[FEATURE] QgsMeshLayer part 1: Reading raw mesh

Introducting MDAL, QgsMeshLayer, mesh data providers (mesh_memory, mdal)
to read and visualize raw meshes: vertices and faces. Support dragging
2dm files from browser on canvas to visualize 2dm meshes.
Support for QgsMeshLayer in Python API.

CMakeLists.txt

@@ -95,6 +95,12 @@ IF(WITH_CORE)
     SET (HAVE_GUI TRUE)     # used in qgsconfig.h
   ENDIF()
 
+  # try to configure and build MDAL support
+  SET (WITH_INTERNAL_MDAL TRUE CACHE BOOL "Determines whether MDAL support should be built")
+  IF (NOT WITH_INTERNAL_MDAL)
+    SET (MDAL_PREFIX "" CACHE PATH "Path to MDAL base directory")
+  ENDIF (NOT WITH_INTERNAL_MDAL)
+
   # try to configure and build POSTGRESQL support
   SET (WITH_POSTGRESQL TRUE CACHE BOOL "Determines whether POSTGRESQL support should be built")
   IF (WITH_POSTGRESQL)
@@ -258,6 +264,10 @@ IF(WITH_CORE)
     FIND_PACKAGE(Postgres) # PostgreSQL provider
   ENDIF (WITH_POSTGRESQL)
 
+  IF (NOT WITH_INTERNAL_MDAL)
+    FIND_PACKAGE(MDAL REQUIRED) # MDAL provider
+  ENDIF (NOT WITH_INTERNAL_MDAL)
+
   FIND_PACKAGE(SpatiaLite REQUIRED)
 
   IF (NOT PROJ_FOUND OR NOT GEOS_FOUND OR NOT GDAL_FOUND)

cmake/FindMDAL.cmake

@@ -0,0 +1,32 @@
+# Find MDAL
+# ~~~~~~~~~
+# Copyright (c) 2018, Peter Petrik <zilolv at gmail dot com>
+# Redistribution and use is allowed according to the terms of the BSD license.
+# For details see the accompanying COPYING-CMAKE-SCRIPTS file.
+#
+#
+# Once run this will define: 
+#  MDAL_FOUND - System has MDAL
+#  MDAL_INCLUDE_DIRS - The MDAL include directories
+#  MDAL_LIBRARIES - The libraries needed to use MDAL
+#  MDAL_DEFINITIONS - Compiler switches required for using MDAL
+
+FIND_PACKAGE(PkgConfig)
+PKG_CHECK_MODULES(PC_MDAL QUIET libmdal)
+SET(MDAL_DEFINITIONS ${PC_MDAL_CFLAGS_OTHER})
+
+FIND_PATH(MDAL_INCLUDE_DIR mdal.h
+          HINTS ${PC_MDAL_INCLUDEDIR} ${PC_MDAL_INCLUDE_DIRS} ${MDAL_PREFIX}/include
+          PATH_SUFFIXES libmdal )
+
+FIND_LIBRARY(MDAL_LIBRARY NAMES mdal libmdal
+             HINTS ${PC_MDAL_LIBDIR} ${PC_MDAL_LIBRARY_DIRS} ${MDAL_PREFIX}/lib)
+
+INCLUDE(FindPackageHandleStandardArgs)
+FIND_PACKAGE_HANDLE_STANDARD_ARGS(MDAL DEFAULT_MSG
+                                  MDAL_LIBRARY MDAL_INCLUDE_DIR)
+
+MARK_AS_ADVANCED(MDAL_INCLUDE_DIR MDAL_LIBRARY )
+
+SET(MDAL_LIBRARIES ${MDAL_LIBRARY} )
+SET(MDAL_INCLUDE_DIRS ${MDAL_INCLUDE_DIR} )

external/mdal/api/mdal.h

@@ -0,0 +1,91 @@
+/*
+ MDAL - Mesh Data Abstraction Library (MIT License)
+ Copyright (C) 2018 Peter Petrik (zilolv at gmail dot com)
+*/
+
+#ifndef MDAL_H
+#define MDAL_H
+
+#ifdef MDAL_STATIC
+#  define MDAL_EXPORT
+#else
+#  if defined _WIN32 || defined __CYGWIN__
+#    ifdef mdal_EXPORTS
+#      ifdef __GNUC__
+#        define MDAL_EXPORT __attribute__ ((dllexport))
+#      else
+#        define MDAL_EXPORT __declspec(dllexport) // Note: actually gcc seems to also supports this syntax.
+#      endif
+#    else
+#      ifdef __GNUC__
+#        define MDAL_EXPORT __attribute__ ((dllimport))
+#      else
+#        define MDAL_EXPORT __declspec(dllimport) // Note: actually gcc seems to also supports this syntax.
+#      endif
+#    endif
+#  else
+#    if __GNUC__ >= 4
+#      define MDAL_EXPORT __attribute__ ((visibility ("default")))
+#    else
+#      define MDAL_EXPORT
+#    endif
+#  endif
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stddef.h>
+
+/* Statuses */
+enum Status
+{
+  None,
+  // Errors
+  Err_NotEnoughMemory,
+  Err_FileNotFound,
+  Err_UnknownFormat,
+  Err_IncompatibleMesh,
+  Err_InvalidData,
+  Err_MissingDriver,
+  // Warnings
+  Warn_UnsupportedElement,
+  Warn_InvalidElements,
+  Warn_ElementWithInvalidNode,
+  Warn_ElementNotUnique,
+  Warn_NodeNotUnique
+};
+
+/* Mesh */
+typedef void *MeshH;
+
+//! Return MDAL version
+MDAL_EXPORT const char *MDAL_Version();
+
+//! Return last status message
+MDAL_EXPORT Status MDAL_LastStatus();
+
+//! Load mesh file. On error see MDAL_LastStatus for error type This effectively loads whole mesh in-memory
+MDAL_EXPORT MeshH MDAL_LoadMesh( const char *meshFile );
+//! Close mesh, free the memory
+MDAL_EXPORT void MDAL_CloseMesh( MeshH mesh );
+
+//! Return vertex count for the mesh
+MDAL_EXPORT size_t MDAL_M_vertexCount( MeshH mesh );
+//! Return vertex X coord for the mesh
+MDAL_EXPORT double MDAL_M_vertexXCoordinatesAt( MeshH mesh, size_t index );
+//! Return vertex Y coord for the mesh
+MDAL_EXPORT double MDAL_M_vertexYCoordinatesAt( MeshH mesh, size_t index );
+//! Return face count for the mesh
+MDAL_EXPORT size_t MDAL_M_faceCount( MeshH mesh );
+//! Return number of vertices face consist of, e.g. 3 for triangle
+MDAL_EXPORT size_t MDAL_M_faceVerticesCountAt( MeshH mesh, size_t index );
+//! Return vertex index for face
+MDAL_EXPORT size_t MDAL_M_faceVerticesIndexAt( MeshH mesh, size_t face_index, size_t vertex_index );
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif //MDAL_H

external/mdal/frmts/mdal_2dm.cpp

@@ -0,0 +1,204 @@
+/*
+ MDAL - Mesh Data Abstraction Library (MIT License)
+ Copyright (C) 2018 Peter Petrik (zilolv at gmail dot com)
+*/
+
+#include <stddef.h>
+#include <iosfwd>
+#include <iostream>
+#include <fstream>
+#include <sstream>
+#include <string>
+#include <vector>
+#include <map>
+#include <cassert>
+
+#include "mdal_2dm.hpp"
+#include "mdal.h"
+#include "mdal_utils.hpp"
+
+MDAL::Loader2dm::Loader2dm( const std::string &meshFile ):
+  mMeshFile( meshFile )
+{
+}
+
+MDAL::Mesh *MDAL::Loader2dm::load( Status *status )
+{
+  if ( status ) *status = Status::None;
+
+  if ( !MDAL::fileExists( mMeshFile ) )
+  {
+    if ( status ) *status = Status::Err_FileNotFound;
+    return 0;
+  }
+
+  std::ifstream in( mMeshFile, std::ifstream::in );
+  std::string line;
+  if ( !std::getline( in, line ) || !startsWith( line, "MESH2D" ) )
+  {
+    if ( status ) *status = Status::Err_UnknownFormat;
+    return 0;
+  }
+
+  size_t elemCount = 0;
+  size_t nodeCount = 0;
+
+  // Find out how many nodes and elements are contained in the .2dm mesh file
+  while ( std::getline( in, line ) )
+  {
+    if ( startsWith( line, "E4Q" ) ||
+         startsWith( line, "E3T" ) )
+    {
+      elemCount++;
+    }
+    else if ( startsWith( line, "ND" ) )
+    {
+      nodeCount++;
+    }
+    else if ( startsWith( line, "E2L" ) ||
+              startsWith( line, "E3L" ) ||
+              startsWith( line, "E6T" ) ||
+              startsWith( line, "E8Q" ) ||
+              startsWith( line, "E9Q" ) )
+    {
+      if ( status ) *status = Status::Warn_UnsupportedElement;
+      elemCount += 1; // We still count them as elements
+    }
+  }
+
+  // Allocate memory
+  std::vector<Vertex> vertices( nodeCount );
+  std::vector<Face> faces( elemCount );
+
+  in.clear();
+  in.seekg( 0, std::ios::beg );
+
+  std::vector<std::string> chunks;
+
+  size_t elemIndex = 0;
+  size_t nodeIndex = 0;
+  std::map<size_t, size_t> elemIDtoIndex;
+  std::map<size_t, size_t> nodeIDtoIndex;
+
+  while ( std::getline( in, line ) )
+  {
+    if ( startsWith( line, "E4Q" ) )
+    {
+      chunks = split( line,  " ", SplitBehaviour::SkipEmptyParts );
+      assert( elemIndex < elemCount );
+
+      size_t elemID = toSizeT( chunks[1] );
+
+      std::map<size_t, size_t>::iterator search = elemIDtoIndex.find( elemID );
+      if ( search != elemIDtoIndex.end() )
+      {
+        if ( status ) *status = Status::Warn_ElementNotUnique;
+        continue;
+      }
+      elemIDtoIndex[elemID] = elemIndex;
+      Face &face = faces[elemIndex];
+      face.resize( 4 );
+      // Right now we just store node IDs here - we will convert them to node indices afterwards
+      for ( size_t i = 0; i < 4; ++i )
+        face[i] = toSizeT( chunks[i + 2] );
+
+      elemIndex++;
+    }
+    else if ( startsWith( line, "E3T" ) )
+    {
+      chunks = split( line,  " ", SplitBehaviour::SkipEmptyParts );
+      assert( elemIndex < elemCount );
+
+      size_t elemID = toSizeT( chunks[1] );
+
+      std::map<size_t, size_t>::iterator search = elemIDtoIndex.find( elemID );
+      if ( search != elemIDtoIndex.end() )
+      {
+        if ( status ) *status = Status::Warn_ElementNotUnique;
+        continue;
+      }
+      elemIDtoIndex[elemID] = elemIndex;
+      Face &face = faces[elemIndex];
+      face.resize( 3 );
+      // Right now we just store node IDs here - we will convert them to node indices afterwards
+      for ( size_t i = 0; i < 3; ++i )
+      {
+        face[i] = toSizeT( chunks[i + 2] );
+      }
+
+      elemIndex++;
+    }
+    else if ( startsWith( line, "E2L" ) ||
+              startsWith( line, "E3L" ) ||
+              startsWith( line, "E6T" ) ||
+              startsWith( line, "E8Q" ) ||
+              startsWith( line, "E9Q" ) )
+    {
+      // We do not yet support these elements
+      chunks = split( line,  " ", SplitBehaviour::SkipEmptyParts );
+      assert( elemIndex < elemCount );
+
+      size_t elemID = toSizeT( chunks[1] );
+
+      std::map<size_t, size_t>::iterator search = elemIDtoIndex.find( elemID );
+      if ( search != elemIDtoIndex.end() )
+      {
+        if ( status ) *status = Status::Warn_ElementNotUnique;
+        continue;
+      }
+      elemIDtoIndex[elemID] = elemIndex;
+      assert( false ); //TODO mark element as unusable
+
+      elemIndex++;
+    }
+    else if ( startsWith( line, "ND" ) )
+    {
+      chunks = split( line,  " ", SplitBehaviour::SkipEmptyParts );
+      size_t nodeID = toSizeT( chunks[1] );
+
+      std::map<size_t, size_t>::iterator search = nodeIDtoIndex.find( nodeID );
+      if ( search != nodeIDtoIndex.end() )
+      {
+        if ( status ) *status = Status::Warn_NodeNotUnique;
+        continue;
+      }
+      nodeIDtoIndex[nodeID] = nodeIndex;
+      assert( nodeIndex < nodeCount );
+      Vertex &vertex = vertices[nodeIndex];
+      vertex.x = toDouble( chunks[2] );
+      vertex.y = toDouble( chunks[3] );
+
+      nodeIndex++;
+    }
+  }
+
+  for ( std::vector<Face>::iterator it = faces.begin(); it != faces.end(); ++it )
+  {
+    Face &face = *it;
+    for ( Face::size_type nd = 0; nd < face.size(); ++nd )
+    {
+      size_t nodeID = face[nd];
+
+      std::map<size_t, size_t>::iterator ni2i = nodeIDtoIndex.find( nodeID );
+      if ( ni2i != nodeIDtoIndex.end() )
+      {
+        face[nd] = ni2i->second; // convert from ID to index
+      }
+      else
+      {
+        assert( false ); //TODO mark element as unusable
+
+        if ( status ) *status = Status::Warn_ElementWithInvalidNode;
+      }
+    }
+
+    //TODO check validity of the face
+    //check that we have distinct nodes
+  }
+
+  Mesh *mesh = new Mesh;
+  mesh->faces = faces;
+  mesh->vertices = vertices;
+
+  return mesh;
+}

external/mdal/frmts/mdal_2dm.hpp

@@ -0,0 +1,28 @@
+/*
+ MDAL - Mesh Data Abstraction Library (MIT License)
+ Copyright (C) 2018 Peter Petrik (zilolv at gmail dot com)
+*/
+
+#ifndef MDAL_2DM_HPP
+#define MDAL_2DM_HPP
+
+#include <string>
+
+#include "mdal_defines.hpp"
+#include "mdal.h"
+
+namespace MDAL
+{
+
+  class Loader2dm
+  {
+    public:
+      Loader2dm( const std::string &meshFile );
+      Mesh *load( Status *status );
+
+    private:
+      std::string mMeshFile;
+  };
+
+} // namespace MDAL
+#endif //MDAL_2DM_HPP

external/mdal/mdal.cpp

@@ -0,0 +1,86 @@
+#include <string>
+#include <cassert>
+#include <stddef.h>
+
+#include "mdal.h"
+#include "mdal_loader.hpp"
+#include "mdal_defines.hpp"
+
+static Status sLastStatus;
+
+const char *MDAL_Version()
+{
+  return "0.0.1";
+}
+
+Status MDAL_LastStatus()
+{
+  return sLastStatus;
+}
+
+MeshH MDAL_LoadMesh( const char *meshFile )
+{
+  if ( !meshFile )
+    return nullptr;
+
+  std::string filename( meshFile );
+  return ( MeshH ) MDAL::Loader::load( filename, &sLastStatus );
+}
+
+
+void MDAL_CloseMesh( MeshH mesh )
+{
+  if ( mesh )
+  {
+    MDAL::Mesh *m = ( MDAL::Mesh * ) mesh;
+    delete m;
+  }
+}
+
+
+size_t MDAL_M_vertexCount( MeshH mesh )
+{
+  assert( mesh );
+  MDAL::Mesh *m = ( MDAL::Mesh * ) mesh;
+  return m->vertices.size();
+}
+
+double MDAL_M_vertexXCoordinatesAt( MeshH mesh, size_t index )
+{
+  assert( mesh );
+  MDAL::Mesh *m = ( MDAL::Mesh * ) mesh;
+  assert( m->vertices.size() > index );
+  return m->vertices[index].x;
+}
+
+double MDAL_M_vertexYCoordinatesAt( MeshH mesh, size_t index )
+{
+  assert( mesh );
+  MDAL::Mesh *m = ( MDAL::Mesh * ) mesh;
+  assert( m->vertices.size() > index );
+  return m->vertices[index].y;
+}
+
+size_t MDAL_M_faceCount( MeshH mesh )
+{
+  assert( mesh );
+  MDAL::Mesh *m = ( MDAL::Mesh * ) mesh;
+  return m->faces.size();
+}
+
+size_t MDAL_M_faceVerticesCountAt( MeshH mesh, size_t index )
+{
+  assert( mesh );
+  MDAL::Mesh *m = ( MDAL::Mesh * ) mesh;
+  assert( m->faces.size() > index );
+  return m->faces[index].size();
+}
+
+size_t MDAL_M_faceVerticesIndexAt( MeshH mesh, size_t face_index, size_t vertex_index )
+{
+  assert( mesh );
+  MDAL::Mesh *m = ( MDAL::Mesh * ) mesh;
+  assert( m->faces.size() > face_index );
+  assert( m->faces[face_index].size() > vertex_index );
+  return m->faces[face_index][vertex_index];
+}

external/mdal/mdal_defines.hpp

@@ -0,0 +1,31 @@
+/*
+ MDAL - Mesh Data Abstraction Library (MIT License)
+ Copyright (C) 2018 Peter Petrik (zilolv at gmail dot com)
+*/
+
+#ifndef MDAL_DEFINES_HPP
+#define MDAL_DEFINES_HPP
+
+#include <stddef.h>
+#include <vector>
+
+namespace MDAL
+{
+
+  typedef struct
+  {
+    double x;
+    double y;
+  } Vertex;
+
+  typedef std::vector<size_t> Face;
+
+  struct Mesh
+  {
+    std::vector<Vertex> vertices;
+    std::vector<Face> faces;
+  };
+
+} // namespace MDAL
+#endif //MDAL_DEFINES_HPP
+

external/mdal/mdal_loader.cpp

@@ -0,0 +1,13 @@
+/*
+ MDAL - Mesh Data Abstraction Library (MIT License)
+ Copyright (C) 2018 Peter Petrik (zilolv at gmail dot com)
+*/
+
+#include "mdal_loader.hpp"
+#include "frmts/mdal_2dm.hpp"
+
+MDAL::Mesh *MDAL::Loader::load( const std::string &meshFile, Status *status )
+{
+  MDAL::Loader2dm loader( meshFile );
+  return loader.load( status );
+}

external/mdal/mdal_loader.hpp

@@ -0,0 +1,24 @@
+/*
+ MDAL - Mesh Data Abstraction Library (MIT License)
+ Copyright (C) 2018 Peter Petrik (zilolv at gmail dot com)
+*/
+
+#ifndef MDAL_LOADER_HPP
+#define MDAL_LOADER_HPP
+
+#include <string>
+
+#include "mdal.h"
+#include "mdal_defines.hpp"
+
+namespace MDAL
+{
+
+  class Loader
+  {
+    public:
+      static Mesh *load( const std::string &meshFile, Status *status );
+  };
+
+} // namespace MDAL
+#endif //MDAL_LOADER_HPP

external/mdal/mdal_utils.cpp

@@ -0,0 +1,56 @@
+/*
+ MDAL - Mesh Data Abstraction Library (MIT License)
+ Copyright (C) 2018 Peter Petrik (zilolv at gmail dot com)
+*/
+
+#include "mdal_utils.hpp"
+#include <fstream>
+
+bool MDAL::fileExists( const std::string &filename )
+{
+  std::ifstream in( filename );
+  return in.good();
+}
+
+
+bool MDAL::startsWith( const std::string &str, const std::string &substr )
+{
+  return str.rfind( substr, 0 ) == 0;
+}
+
+std::vector<std::string> MDAL::split( const std::string &str, const std::string &delimiter, SplitBehaviour behaviour )
+{
+  std::string remaining( str );
+  std::vector<std::string> list;
+  size_t pos = 0;
+  std::string token;
+  while ( ( pos = remaining.find( delimiter ) ) != std::string::npos )
+  {
+    token = remaining.substr( 0, pos );
+
+    if ( behaviour == SplitBehaviour::SkipEmptyParts )
+    {
+      if ( !token.empty() )
+        list.push_back( token );
+    }
+    else
+      list.push_back( token );
+
+    remaining.erase( 0, pos + delimiter.length() );
+  }
+  list.push_back( remaining );
+  return list;
+}
+
+size_t MDAL::toSizeT( const std::string &str )
+{
+  int i = atoi( str.c_str() );
+  if ( i < 0 ) // consistent with atoi return
+    i = 0;
+  return i;
+}
+
+double MDAL::toDouble( const std::string &str )
+{
+  return atof( str.c_str() );
+}

external/mdal/mdal_utils.hpp

@@ -0,0 +1,34 @@
+/*
+ MDAL - Mesh Data Abstraction Library (MIT License)
+ Copyright (C) 2018 Peter Petrik (zilolv at gmail dot com)
+*/
+
+#ifndef MDAL_UTILS_HPP
+#define MDAL_UTILS_HPP
+
+#include <string>
+#include <vector>
+#include <stddef.h>
+
+namespace MDAL
+{
+
+  /** Return whether file exists */
+  bool fileExists( const std::string &filename );
+
+  // strings
+  bool startsWith( const std::string &str, const std::string &substr );
+
+  /** Return 0 if not possible to convert */
+  size_t toSizeT( const std::string &str );
+  double toDouble( const std::string &str );
+
+  enum SplitBehaviour
+  {
+    SkipEmptyParts,
+    KeepEmptyParts
+  };
+  std::vector<std::string> split( const std::string &str, const std::string &delimiter, SplitBehaviour behaviour );
+
+} // namespace MDAL
+#endif //MDAL_UTILS_HPP

python/CMakeLists.txt

@@ -119,6 +119,7 @@ INCLUDE_DIRECTORIES(
   ${CMAKE_SOURCE_DIR}/src/core/layout
   ${CMAKE_SOURCE_DIR}/src/core/locator
   ${CMAKE_SOURCE_DIR}/src/core/metadata
+  ${CMAKE_SOURCE_DIR}/src/core/mesh
   ${CMAKE_SOURCE_DIR}/src/core/processing
   ${CMAKE_SOURCE_DIR}/src/core/processing/models
   ${CMAKE_SOURCE_DIR}/src/core/providers

python/core/core_auto.sip

@@ -433,3 +433,6 @@
 %Include qgsuserprofilemanager.sip
 %Include symbology/qgsarrowsymbollayer.sip
 %Include qgsuserprofile.sip
+%Include mesh/qgsmeshdataprovider.sip
+%Include mesh/qgsmeshlayer.sip
+

python/core/mesh/qgsmeshdataprovider.sip.in

@@ -0,0 +1,98 @@
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/mesh/qgsmeshdataprovider.h                                  *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/
+
+
+
+
+
+
+typedef QgsPoint QgsMeshVertex; //xyz coords of vertex
+typedef QVector<size_t> QgsMeshFace; //list of vertex indexes
+
+class QgsMeshSource /Abstract/
+{
+%Docstring
+Mesh is a  collection of vertices and faces in 2D or 3D space
+- vertex - XY(Z) point (in the mesh's coordinate reference system)
+- faces - sets of vertices forming a closed shape - typically triangles or quadrilaterals
+
+Base on the underlying data provider/format, whole mesh is either stored in memory or
+read on demand
+
+.. versionadded:: 3.2
+%End
+
+%TypeHeaderCode
+#include "qgsmeshdataprovider.h"
+%End
+  public:
+    virtual ~QgsMeshSource();
+
+    virtual size_t vertexCount() const = 0;
+%Docstring
+ Return number of vertexes in the native mesh
+
+:return: Number of vertexes in the mesh
+%End
+
+    virtual size_t faceCount() const = 0;
+%Docstring
+ Return number of faces in the native mesh
+
+:return: Number of faces in the mesh
+%End
+
+    virtual QgsMeshVertex vertex( size_t index ) const = 0;
+%Docstring
+ Factory for mesh vertex with index
+
+:return: new mesh vertex on index
+%End
+
+    virtual QgsMeshFace face( size_t index ) const = 0;
+%Docstring
+ Factory for mesh face with index
+
+:return: new mesh face on index
+%End
+};
+
+class QgsMeshDataProvider: QgsDataProvider, QgsMeshSource
+{
+%Docstring
+Base class for providing data for :py:class:`QgsMeshLayer`
+
+Responsible for reading native mesh data
+
+.. seealso:: :py:class:`QgsMeshSource`
+%End
+
+%TypeHeaderCode
+#include "qgsmeshdataprovider.h"
+%End
+  public:
+    QgsMeshDataProvider( const QString &uri = QString() );
+%Docstring
+Ctor
+%End
+
+    virtual QgsRectangle extent() const;
+%Docstring
+Returns the extent of the layer
+
+:return: QgsRectangle containing the extent of the layer
+%End
+};
+
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/mesh/qgsmeshdataprovider.h                                  *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/

python/core/mesh/qgsmeshlayer.sip.in

@@ -0,0 +1,174 @@
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/mesh/qgsmeshlayer.h                                         *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/
+
+
+
+
+
+
+
+class QgsMeshLayer : QgsMapLayer
+{
+%Docstring
+
+Represents a mesh layer supporting display of data on structured or unstructured meshes
+
+The QgsMeshLayer is instantiated by specifying the name of a data provider,
+such as mdal, and url defining the specific data set to connect to.
+The vector layer constructor in turn instantiates a QgsMeshDataProvider subclass
+corresponding to the provider type, and passes it the url. The data provider
+connects to the data source.
+
+The QgsMeshLayer provides a common interface to the different data types. It does not
+yet support editing transactions.
+
+The main data providers supported by QGIS are listed below.
+
+\section providers Mesh data providers
+
+\subsection memory Memory data providerType (mesh_memory)
+
+The memory data provider is used to construct in memory data, for example scratch
+data. There is no inherent persistent storage of the data. The data source uri is constructed.
+Data can be populated by setMesh(const QString &vertices, const QString &faces), where
+vertices and faces is comma separated coordinates and connections for mesh.
+E.g. to create mesh with one quad and one triangle
+
+.. code-block::
+
+      QString uri(
+          "1.0, 2.0 \n" \
+          "2.0, 2.0 \n" \
+          "3.0, 2.0 \n" \
+          "2.0, 3.0 \n" \
+          "1.0, 3.0 \n" \
+          "---"
+          "0, 1, 3, 4 \n" \
+          "1, 2, 3 \n"
+        );
+        QgsMeshLayer *scratchLayer = new QgsMeshLayer(uri, "My Scratch layer", "memory_mesh");
+
+\subsection mdal MDAL data provider (mdal)
+
+Accesses data using the MDAL drivers (https://github.com/lutraconsulting/MDAL). The url
+is the MDAL connection string. QGIS must be built with MDAL support to allow this provider.
+
+.. code-block::
+
+         QString uri = "test/land.2dm";
+         QgsMeshLayer *scratchLayer = new QgsMeshLayer(uri, "My Scratch Layer",  "mdal");
+
+.. versionadded:: 3.2
+%End
+
+%TypeHeaderCode
+#include "qgsmeshlayer.h"
+%End
+  public:
+
+    explicit QgsMeshLayer( const QString &path = QString(), const QString &baseName = QString(), const QString &providerLib = "mesh_memory" );
+%Docstring
+Constructor - creates a mesh layer
+
+The QgsMeshLayer is constructed by instantiating a data provider.  The provider
+interprets the supplied path (url) of the data source to connect to and access the
+data.
+
+:param path:  The path or url of the parameter.  Typically this encodes
+parameters used by the data provider as url query items.
+:param baseName: The name used to represent the layer in the legend
+:param providerLib:  The name of the data provider, e.g., "mesh_memory", "mdal"
+%End
+    ~QgsMeshLayer();
+
+
+    virtual QgsMeshDataProvider *dataProvider();
+
+%Docstring
+Return data provider
+%End
+
+
+    virtual QgsMeshLayer *clone() const /Factory/;
+
+%Docstring
+Returns a new instance equivalent to this one. A new provider is
+created for the same data source and renderers are cloned too.
+
+:return: a new layer instance
+%End
+
+    virtual QgsRectangle extent() const;
+
+%Docstring
+Returns the extent of the layer.
+%End
+
+    virtual QgsMapLayerRenderer *createMapRenderer( QgsRenderContext &rendererContext ) /Factory/;
+%Docstring
+Return new instance of QgsMapLayerRenderer that will be used for rendering of given context
+%End
+
+    QString providerType() const;
+%Docstring
+Return the provider type for this layer
+%End
+
+
+
+    QgsSymbol *nativeMeshSymbol();
+%Docstring
+Returns a line symbol used for rendering native mesh.
+%End
+
+    QgsSymbol *triangularMeshSymbol();
+%Docstring
+Returns a line symbol used for rendering of triangular (derived) mesh.
+
+.. seealso:: :py:func:`toggleTriangularMeshRendering`
+%End
+
+    void toggleTriangularMeshRendering( bool toggle );
+%Docstring
+Toggle rendering of triangular (derived) mesh. Off by default
+%End
+
+    bool readSymbology( const QDomNode &node, QString &errorMessage, QgsReadWriteContext &context );
+%Docstring
+Read the symbology for the current layer from the Dom node supplied.
+
+:param node: node that will contain the symbology definition for this layer.
+:param errorMessage: reference to string that will be updated with any error messages
+:param context: reading context (used for transform from relative to absolute paths)
+
+:return: true in case of success.
+%End
+
+    bool writeSymbology( QDomNode &node, QDomDocument &doc, QString &errorMessage, const QgsReadWriteContext &context ) const;
+%Docstring
+Write the symbology for the layer into the docment provided.
+
+:param node: the node that will have the style element added to it.
+:param doc: the document that will have the QDomNode added.
+:param errorMessage: reference to string that will be updated with any error messages
+:param context: writing context (used for transform from absolute to relative paths)
+
+:return: true in case of success.
+%End
+
+  private:                       // Private methods
+    QgsMeshLayer( const QgsMeshLayer &rhs );
+};
+
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/mesh/qgsmeshlayer.h                                         *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/

python/core/mesh/qgsnativemesh.sip.in

@@ -0,0 +1,28 @@
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/mesh/qgsnativemesh.h                                        *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/
+
+
+
+
+
+typedef QgsPoint QgsMeshVertex; //xyz coords of vertex
+typedef std::vector<int> QgsMeshFace; //list of vertex indexes
+
+struct QgsNativeMesh
+{
+  std::vector<QgsMeshVertex> vertices;
+  std::vector<QgsMeshFace> faces;
+};
+
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/mesh/qgsnativemesh.h                                        *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/

python/core/qgsdataitem.sip.in

@@ -394,7 +394,8 @@ Item that represents a layer that can be opened with one of the providers
       TableLayer,
       Database,
       Table,
-      Plugin
+      Plugin,
+      Mesh
     };
 
 
@@ -470,6 +471,7 @@ Returns the icon name of the given ``layerType``
     static QIcon iconTable();
     static QIcon iconRaster();
     static QIcon iconDefault();
+    static QIcon iconMesh();
 
     virtual QString layerName() const;
 %Docstring

python/core/qgsdataprovider.sip.in

@@ -38,6 +38,10 @@ to generic QgsVectorDataProvider's) depends on it.
     {
       sipType = sipType_QgsRasterDataProvider;
     }
+    else if ( qobject_cast<QgsMeshDataProvider *>( sipCpp ) )
+    {
+      sipType = sipType_QgsMeshDataProvider;
+    }
     else
     {
       sipType = 0;

python/core/qgsmaplayer.sip.in

@@ -41,6 +41,9 @@ This is the base class for all map layer types (vector, raster).
         case QgsMapLayer::PluginLayer:
           sipType = sipType_QgsPluginLayer;
           break;
+        case QgsMapLayer::MeshLayer:
+          sipType = sipType_QgsMeshLayer;
+          break;
         default:
           sipType = nullptr;
           break;
@@ -53,7 +56,8 @@ This is the base class for all map layer types (vector, raster).
     {
       VectorLayer,
       RasterLayer,
-      PluginLayer
+      PluginLayer,
+      MeshLayer
     };
 
     enum PropertyType

python/core/qgsmimedatautils.sip.in

@@ -52,6 +52,14 @@ Get vector layer from uri if possible, otherwise returns 0 and error is set
 %Docstring
 Get raster layer from uri if possible, otherwise returns 0 and error is set
 
+:param owner: set to true if caller becomes owner
+:param error: set to error message if cannot get raster
+%End
+
+      QgsMeshLayer *meshLayer( bool &owner, QString &error ) const;
+%Docstring
+Get mesh layer from uri if possible, otherwise returns 0 and error is set
+
 :param owner: set to true if caller becomes owner
 :param error: set to error message if cannot get raster
 %End

python/core/qgsproviderregistry.sip.in

@@ -162,6 +162,7 @@ buildSupportedRasterFileFilter to a string, which is then returned.
 
    This replaces :py:func:`QgsRasterLayer.buildSupportedRasterFileFilter()`
 %End
+
     virtual QString databaseDrivers() const;
 %Docstring
 Return a string containing the available database drivers

src/analysis/processing/qgsalgorithmpackage.cpp

@@ -142,6 +142,12 @@ QVariantMap QgsPackageAlgorithm::processAlgorithm( const QVariantMap &parameters
         feedback->pushDebugInfo( QObject::tr( "Packaging plugin layers is not supported." ) );
         errored = true;
         break;
+
+      case QgsMapLayer::MeshLayer:
+        //not supported
+        feedback->pushDebugInfo( QObject::tr( "Packaging mesh layers is not supported." ) );
+        errored = true;
+        break;
     }
   }
 

src/app/CMakeLists.txt

@@ -597,6 +597,7 @@ INCLUDE_DIRECTORIES(
   ${CMAKE_SOURCE_DIR}/src/core/geometry
   ${CMAKE_SOURCE_DIR}/src/core/geocms/geonode
   ${CMAKE_SOURCE_DIR}/src/core/metadata
+  ${CMAKE_SOURCE_DIR}/src/core/mesh
   ${CMAKE_SOURCE_DIR}/src/core/layertree
   ${CMAKE_SOURCE_DIR}/src/core/locator
   ${CMAKE_SOURCE_DIR}/src/core/providers/memory

src/app/qgisapp.cpp

@@ -228,6 +228,7 @@ Q_GUI_EXPORT extern int qt_defaultDpiX();
 #include "qgsmessageviewer.h"
 #include "qgsmessagebar.h"
 #include "qgsmessagebaritem.h"
+#include "qgsmeshlayer.h"
 #include "qgsmemoryproviderutils.h"
 #include "qgsmimedatautils.h"
 #include "qgsmessagelog.h"
@@ -1667,6 +1668,11 @@ void QgisApp::handleDropUriList( const QgsMimeDataUtils::UriList &lst )
     {
       addRasterLayer( uri, u.name, u.providerKey );
     }
+    else if ( u.layerType == QLatin1String( "mesh" ) )
+    {
+      QgsMeshLayer *layer = new QgsMeshLayer( uri, u.name, u.providerKey );
+      addMapLayer( layer );
+    }
     else if ( u.layerType == QLatin1String( "plugin" ) )
     {
       addPluginLayer( uri, u.name, u.providerKey );

src/core/CMakeLists.txt

@@ -446,6 +446,12 @@ SET(QGIS_CORE_SRCS
   raster/qgssinglebandpseudocolorrenderer.cpp
   raster/qgshillshaderenderer.cpp
 
+  mesh/qgsmeshdataprovider.cpp
+  mesh/qgsmeshlayer.cpp
+  mesh/qgsmeshlayerrenderer.cpp
+  mesh/qgsmeshmemorydataprovider.cpp
+  mesh/qgstriangularmesh.cpp
+
   geometry/qgsabstractgeometry.cpp
   geometry/qgsbox3d.cpp
   geometry/qgscircle.cpp
@@ -682,6 +688,10 @@ SET(QGIS_CORE_MOC_HDRS
   raster/qgsrasterlayerrenderer.h
   raster/qgsrasterprojector.h
 
+  mesh/qgsmeshdataprovider.h
+  mesh/qgsmeshlayer.h
+  mesh/qgsmeshmemorydataprovider.h
+
   geometry/qgsabstractgeometry.h
   geometry/qgsgeometry.h
   geometry/qgspoint.h
@@ -1058,6 +1068,9 @@ SET(QGIS_CORE_HDRS
   raster/qgssinglebandpseudocolorrenderer.h
   raster/qgshillshaderenderer.h
 
+  mesh/qgstriangularmesh.h
+  mesh/qgsmeshlayerrenderer.h
+
   scalebar/qgsdoubleboxscalebarrenderer.h
   scalebar/qgsnumericscalebarrenderer.h
   scalebar/qgsscalebarsettings.h
@@ -1177,6 +1190,7 @@ INCLUDE_DIRECTORIES(
   scalebar
   symbology
   metadata
+  mesh
   ${CMAKE_SOURCE_DIR}/external/nmea
 )
 IF (WITH_INTERNAL_QEXTSERIALPORT)

src/core/expression/qgsexpressionfunction.cpp

@@ -3622,6 +3622,8 @@ static QVariant fcnGetLayerProperty( const QVariantList &values, const QgsExpres
         return QCoreApplication::translate( "expressions", "Vector" );
       case QgsMapLayer::RasterLayer:
         return QCoreApplication::translate( "expressions", "Raster" );
+      case QgsMapLayer::MeshLayer:
+        return QCoreApplication::translate( "expressions", "Mesh" );
       case QgsMapLayer::PluginLayer:
         return QCoreApplication::translate( "expressions", "Plugin" );
     }

src/core/mesh/qgsmeshdataprovider.cpp

@@ -0,0 +1,40 @@
+/***************************************************************************
+                         qgsmeshdataprovider.cpp
+                         -----------------------
+    begin                : April 2018
+    copyright            : (C) 2018 by Peter Petrik
+    email                : zilolv at gmail dot com
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgsmeshdataprovider.h"
+
+QgsMeshDataProvider::QgsMeshDataProvider( const QString &uri )
+  : QgsDataProvider( uri )
+{
+}
+
+
+QgsRectangle QgsMeshDataProvider::extent() const
+{
+  QgsRectangle rec;
+  rec.setMinimal();
+  for ( size_t i = 0; i < vertexCount(); ++i )
+  {
+    QgsMeshVertex v = vertex( i );
+    rec.setXMinimum( std::min( rec.xMinimum(), v.x() ) );
+    rec.setYMinimum( std::min( rec.yMinimum(), v.y() ) );
+    rec.setXMaximum( std::max( rec.xMaximum(), v.x() ) );
+    rec.setYMaximum( std::max( rec.yMaximum(), v.y() ) );
+  }
+  return rec;
+
+}

src/core/mesh/qgsmeshdataprovider.h

@@ -0,0 +1,104 @@
+/***************************************************************************
+                         qgsmeshdataprovider.h
+                         ---------------------
+    begin                : April 2018
+    copyright            : (C) 2018 by Peter Petrik
+    email                : zilolv at gmail dot com
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef QGSMESHDATAPROVIDER_H
+#define QGSMESHDATAPROVIDER_H
+
+#include <cstddef>
+
+#include "qgis_core.h"
+#include "qgis.h"
+#include "qgspoint.h"
+#include "qgsrectangle.h"
+#include "qgsdataprovider.h"
+#include "qgscoordinatereferencesystem.h"
+
+#include <QVector>
+#include <QHash>
+#include <QString>
+#include <QVariant>
+
+typedef QgsPoint QgsMeshVertex; //xyz coords of vertex
+typedef QVector<size_t> QgsMeshFace; //list of vertex indexes
+
+/**
+ * \ingroup core
+ * Mesh is a  collection of vertices and faces in 2D or 3D space
+ *  - vertex - XY(Z) point (in the mesh's coordinate reference system)
+ *  - faces - sets of vertices forming a closed shape - typically triangles or quadrilaterals
+ *
+ * Base on the underlying data provider/format, whole mesh is either stored in memory or
+ * read on demand
+ *
+ * \since QGIS 3.2
+ */
+class CORE_EXPORT QgsMeshSource SIP_ABSTRACT
+{
+  public:
+    //! Dtor
+    virtual ~QgsMeshSource() = default;
+
+    /**
+     * \brief Return number of vertexes in the native mesh
+     * \returns Number of vertexes in the mesh
+     */
+    virtual size_t vertexCount() const = 0;
+
+    /**
+     * \brief Return number of faces in the native mesh
+     * \returns Number of faces in the mesh
+     */
+    virtual size_t faceCount() const = 0;
+
+    /**
+     * \brief Factory for mesh vertex with index
+     * \returns new mesh vertex on index
+     */
+    virtual QgsMeshVertex vertex( size_t index ) const = 0;
+
+    /**
+     * \brief Factory for mesh face with index
+     * \returns new mesh face on index
+     */
+    virtual QgsMeshFace face( size_t index ) const = 0;
+};
+
+/**
+ * \ingroup core
+  * Base class for providing data for QgsMeshLayer
+  *
+  * Responsible for reading native mesh data
+  *
+  * \see QgsMeshSource
+  *
+  */
+class CORE_EXPORT QgsMeshDataProvider: public QgsDataProvider, public QgsMeshSource
+{
+    Q_OBJECT
+
+  public:
+    //! Ctor
+    QgsMeshDataProvider( const QString &uri = QString() );
+
+    /**
+     * Returns the extent of the layer
+     * \returns QgsRectangle containing the extent of the layer
+     */
+    virtual QgsRectangle extent() const;
+};
+
+#endif // QGSMESHDATAPROVIDER_H

src/core/mesh/qgsmeshlayer.cpp

@@ -0,0 +1,217 @@
+/***************************************************************************
+                         qgsmeshlayer.cpp
+                         ----------------
+    begin                : April 2018
+    copyright            : (C) 2018 by Peter Petrik
+    email                : zilolv at gmail dot com
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+#include <QUuid>
+
+#include "qgsmeshlayer.h"
+#include "qgis.h"
+#include "qgsmaplayerrenderer.h"
+#include "qgsmeshdataprovider.h"
+#include "qgsmeshlayerrenderer.h"
+#include "qgstriangularmesh.h"
+#include "qgssinglesymbolrenderer.h"
+#include "qgsmeshmemorydataprovider.h"
+#include "qgsfillsymbollayer.h"
+#include "qgsproviderregistry.h"
+#include "qgslogger.h"
+
+QgsMeshLayer::QgsMeshLayer( const QString &meshLayerPath,
+                            const QString &baseName,
+                            const QString &providerKey )
+  : QgsMapLayer( MeshLayer, baseName, meshLayerPath )
+  , mProviderKey( providerKey )
+{
+  // load data
+  setDataProvider( providerKey );
+
+  QgsSymbolLayerList l1;
+  l1 << new QgsSimpleFillSymbolLayer( Qt::white, Qt::NoBrush, Qt::black, Qt::SolidLine, 1.0 );
+  mNativeMeshSymbol = new QgsFillSymbol( l1 );
+
+
+  toggleTriangularMeshRendering( false );
+
+} // QgsMeshLayer ctor
+
+
+
+QgsMeshLayer::~QgsMeshLayer()
+{
+  clearMeshes();
+
+  if ( mDataProvider )
+    delete mDataProvider;
+
+  if ( mNativeMeshSymbol )
+    delete mNativeMeshSymbol;
+
+  if ( mTriangularMeshSymbol )
+    delete mTriangularMeshSymbol;
+}
+
+QgsMeshDataProvider *QgsMeshLayer::dataProvider()
+{
+  return mDataProvider;
+}
+
+const QgsMeshDataProvider *QgsMeshLayer::dataProvider() const
+{
+  return mDataProvider;
+}
+
+QgsMeshLayer *QgsMeshLayer::clone() const
+{
+  QgsMeshLayer *layer = new QgsMeshLayer( source(), name(), mProviderKey );
+  QgsMapLayer::clone( layer );
+  return layer;
+}
+
+QgsRectangle QgsMeshLayer::extent() const
+{
+  if ( mDataProvider )
+    return mDataProvider->extent();
+  else
+  {
+    QgsRectangle rec;
+    rec.setMinimal();
+    return rec;
+  }
+}
+
+QString QgsMeshLayer::providerType() const
+{
+  return mProviderKey;
+}
+
+void QgsMeshLayer::toggleTriangularMeshRendering( bool toggle )
+{
+  if ( toggle && mTriangularMeshSymbol )
+    return;
+
+  if ( mTriangularMeshSymbol )
+    delete mTriangularMeshSymbol;
+
+  if ( toggle )
+  {
+    QgsSymbolLayerList l2;
+    l2 << new QgsSimpleFillSymbolLayer( Qt::white, Qt::NoBrush, Qt::red, Qt::SolidLine, 0.26 );
+    mTriangularMeshSymbol = new QgsFillSymbol( l2 );
+  }
+  else
+  {
+    mTriangularMeshSymbol = nullptr;
+  }
+  triggerRepaint();
+}
+
+void QgsMeshLayer::fillNativeMesh()
+{
+  Q_ASSERT( !mNativeMesh );
+
+  mNativeMesh = new QgsMesh();
+
+  if ( !( dataProvider() && dataProvider()->isValid() ) )
+    return;
+
+  mNativeMesh->vertices.resize( dataProvider()->vertexCount() );
+  for ( size_t i = 0; i < dataProvider()->vertexCount(); ++i )
+  {
+    mNativeMesh->vertices[i] = dataProvider()->vertex( i );
+  }
+
+  mNativeMesh->faces.resize( dataProvider()->faceCount() );
+  for ( size_t i = 0; i < dataProvider()->faceCount(); ++i )
+  {
+    mNativeMesh->faces[i] = dataProvider()->face( i );
+  }
+}
+
+QgsMapLayerRenderer *QgsMeshLayer::createMapRenderer( QgsRenderContext &rendererContext )
+{
+  if ( !mNativeMesh )
+  {
+    fillNativeMesh();
+  }
+
+  if ( !mTriangularMesh )
+    mTriangularMesh = new QgsTriangularMesh();
+
+  triangularMesh()->update( mNativeMesh, &rendererContext );
+  return new QgsMeshLayerRenderer( this, rendererContext );
+}
+
+bool QgsMeshLayer::readSymbology( const QDomNode &node, QString &errorMessage, QgsReadWriteContext &context )
+{
+  Q_UNUSED( node );
+  Q_UNUSED( errorMessage );
+  Q_UNUSED( context );
+  return true;
+}
+
+bool QgsMeshLayer::writeSymbology( QDomNode &node, QDomDocument &doc, QString &errorMessage, const QgsReadWriteContext &context ) const
+{
+  Q_UNUSED( node );
+  Q_UNUSED( doc );
+  Q_UNUSED( errorMessage );
+  Q_UNUSED( context );
+  return true;
+}
+
+void QgsMeshLayer::clearMeshes()
+{
+  if ( mTriangularMesh )
+    delete mTriangularMesh;
+
+  if ( mNativeMesh )
+    delete mNativeMesh;
+
+}
+
+bool QgsMeshLayer::setDataProvider( QString const &provider )
+{
+  clearMeshes();
+
+  mProviderKey = provider;
+  QString dataSource = mDataSource;
+
+  if ( mDataProvider )
+    delete mDataProvider;
+
+  mDataProvider = qobject_cast<QgsMeshDataProvider *>( QgsProviderRegistry::instance()->createProvider( provider, dataSource ) );
+  if ( !mDataProvider )
+  {
+    QgsDebugMsgLevel( QStringLiteral( "Unable to get mesh data provider" ), 2 );
+    return false;
+  }
+
+  mDataProvider->setParent( this );
+  QgsDebugMsgLevel( QStringLiteral( "Instantiated the mesh data provider plugin" ), 2 );
+
+  mValid = mDataProvider->isValid();
+  if ( !mValid )
+  {
+    QgsDebugMsgLevel( QStringLiteral( "Invalid mesh provider plugin %1" ).arg( QString( mDataSource.toUtf8() ) ), 2 );
+    return false;
+  }
+
+  if ( provider == QStringLiteral( "mesh_memory" ) )
+  {
+    // required so that source differs between memory layers
+    mDataSource = mDataSource + QStringLiteral( "&uid=%1" ).arg( QUuid::createUuid().toString() );
+  }
+
+  return true;
+} // QgsMeshLayer:: setDataProvider

src/core/mesh/qgsmeshlayer.h

@@ -0,0 +1,224 @@
+/***************************************************************************
+                         qgsmeshlayer.h
+                         --------------
+    begin                : April 2018
+    copyright            : (C) 2018 by Peter Petrik
+    email                : zilolv at gmail dot com
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef QGSMESHLAYER_H
+#define QGSMESHLAYER_H
+
+#include "qgis_core.h"
+#include <QMap>
+#include <QSet>
+#include <QSharedPointer>
+#include <QList>
+#include <QStringList>
+#include <QFont>
+#include <QMutex>
+
+#include "qgis.h"
+#include "qgsmaplayer.h"
+#include "qgsrendercontext.h"
+#include "qgsmeshdataprovider.h"
+
+class QgsMapLayerRenderer;
+class QgsSymbol;
+
+class QgsMeshDataProvider;
+class QgsNativeMesh;
+class QgsTriangularMesh;
+struct QgsMesh;
+
+/**
+ * \ingroup core
+ *
+ * Represents a mesh layer supporting display of data on structured or unstructured meshes
+ *
+ * The QgsMeshLayer is instantiated by specifying the name of a data provider,
+ * such as mdal, and url defining the specific data set to connect to.
+ * The vector layer constructor in turn instantiates a QgsMeshDataProvider subclass
+ * corresponding to the provider type, and passes it the url. The data provider
+ * connects to the data source.
+ *
+ * The QgsMeshLayer provides a common interface to the different data types. It does not
+ * yet support editing transactions.
+ *
+ * The main data providers supported by QGIS are listed below.
+ *
+ * \section providers Mesh data providers
+ *
+ * \subsection memory Memory data providerType (mesh_memory)
+ *
+ * The memory data provider is used to construct in memory data, for example scratch
+ * data. There is no inherent persistent storage of the data. The data source uri is constructed.
+ * Data can be populated by setMesh(const QString &vertices, const QString &faces), where
+ * vertices and faces is comma separated coordinates and connections for mesh.
+ * E.g. to create mesh with one quad and one triangle
+ *
+ * \code
+ *  QString uri(
+ *      "1.0, 2.0 \n" \
+ *      "2.0, 2.0 \n" \
+ *      "3.0, 2.0 \n" \
+ *      "2.0, 3.0 \n" \
+ *      "1.0, 3.0 \n" \
+ *      "---"
+ *      "0, 1, 3, 4 \n" \
+ *      "1, 2, 3 \n"
+ *    );
+ *    QgsMeshLayer *scratchLayer = new QgsMeshLayer(uri, "My Scratch layer", "memory_mesh");
+ * \endcode
+ *
+ * \subsection mdal MDAL data provider (mdal)
+ *
+ * Accesses data using the MDAL drivers (https://github.com/lutraconsulting/MDAL). The url
+ * is the MDAL connection string. QGIS must be built with MDAL support to allow this provider.
+
+ * \code
+ *     QString uri = "test/land.2dm";
+ *     QgsMeshLayer *scratchLayer = new QgsMeshLayer(uri, "My Scratch Layer",  "mdal");
+ * \endcode
+ *
+ * \since QGIS 3.2
+ */
+class CORE_EXPORT QgsMeshLayer : public QgsMapLayer
+{
+    Q_OBJECT
+  public:
+
+    /**
+     * Constructor - creates a mesh layer
+     *
+     * The QgsMeshLayer is constructed by instantiating a data provider.  The provider
+     * interprets the supplied path (url) of the data source to connect to and access the
+     * data.
+     *
+     * \param path  The path or url of the parameter.  Typically this encodes
+     *               parameters used by the data provider as url query items.
+     * \param baseName The name used to represent the layer in the legend
+     * \param providerLib  The name of the data provider, e.g., "mesh_memory", "mdal"
+     */
+    explicit QgsMeshLayer( const QString &path = QString(), const QString &baseName = QString(), const QString &providerLib = "mesh_memory" );
+    //! Dtor
+    ~QgsMeshLayer() override;
+
+    //! QgsMeshLayer cannot be copied.
+    QgsMeshLayer( const QgsMeshLayer &rhs ) = delete;
+    //! QgsMeshLayer cannot be copied.
+    QgsMeshLayer &operator=( QgsMeshLayer const &rhs ) = delete;
+
+    //! Return data provider
+    QgsMeshDataProvider *dataProvider() override;
+
+    //! Return const data provider
+    const QgsMeshDataProvider *dataProvider() const override SIP_SKIP;
+
+    /**
+     * Returns a new instance equivalent to this one. A new provider is
+     *  created for the same data source and renderers are cloned too.
+     * \returns a new layer instance
+     */
+    QgsMeshLayer *clone() const override SIP_FACTORY;
+
+    //! Returns the extent of the layer.
+    QgsRectangle extent() const override;
+
+    /**
+     * Return new instance of QgsMapLayerRenderer that will be used for rendering of given context
+     */
+    virtual QgsMapLayerRenderer *createMapRenderer( QgsRenderContext &rendererContext ) SIP_FACTORY;
+
+    //! Return the provider type for this layer
+    QString providerType() const;
+
+    //! return native mesh (nullprt before rendering)
+    QgsMesh *nativeMesh() SIP_SKIP {return mNativeMesh;}
+
+    //! return triangular mesh (nullprt before rendering)
+    QgsTriangularMesh *triangularMesh() SIP_SKIP {return mTriangularMesh;}
+
+    //! Returns a line symbol used for rendering native mesh.
+    QgsSymbol *nativeMeshSymbol() {return mNativeMeshSymbol;}
+
+    /**
+     * Returns a line symbol used for rendering of triangular (derived) mesh.
+     * \see toggleTriangularMeshRendering
+     */
+    QgsSymbol *triangularMeshSymbol() {return mTriangularMeshSymbol;}
+
+    //! Toggle rendering of triangular (derived) mesh. Off by default
+    void toggleTriangularMeshRendering( bool toggle );
+
+    /**
+     * Read the symbology for the current layer from the Dom node supplied.
+     * \param node node that will contain the symbology definition for this layer.
+     * \param errorMessage reference to string that will be updated with any error messages
+     * \param context reading context (used for transform from relative to absolute paths)
+     * \returns true in case of success.
+     */
+    bool readSymbology( const QDomNode &node, QString &errorMessage, QgsReadWriteContext &context );
+
+    /**
+     * Write the symbology for the layer into the docment provided.
+     *  \param node the node that will have the style element added to it.
+     *  \param doc the document that will have the QDomNode added.
+     *  \param errorMessage reference to string that will be updated with any error messages
+     *  \param context writing context (used for transform from absolute to relative paths)
+     *  \returns true in case of success.
+     */
+    bool writeSymbology( QDomNode &node, QDomDocument &doc, QString &errorMessage, const QgsReadWriteContext &context ) const;
+
+  private:                       // Private methods
+
+    /**
+     * Returns true if the provider is in read-only mode
+     */
+    bool isReadOnly() const override {return true;}
+
+    /**
+     * Bind layer to a specific data provider
+     * \param provider provider key string, must match a valid QgsMeshDataProvider key. E.g. "mesh_memory", etc.
+     */
+    bool setDataProvider( QString const &provider );
+
+#ifdef SIP_RUN
+    QgsMeshLayer( const QgsMeshLayer &rhs );
+#endif
+
+  private:
+    //! Clear native and triangular mesh
+    void clearMeshes();
+    void fillNativeMesh();
+
+  private:
+    //! Pointer to native mesh structure, used as cache for rendering
+    QgsMesh *mNativeMesh = nullptr;
+
+    //! Pointer to derived mesh structure
+    QgsTriangularMesh *mTriangularMesh = nullptr;
+
+    //! Pointer to data provider derived from the abastract base class QgsMeshDataProvider
+    QgsMeshDataProvider *mDataProvider = nullptr;
+
+    //! Data provider key
+    QString mProviderKey;
+
+    //! rendering native mesh
+    QgsSymbol *mNativeMeshSymbol = nullptr;
+
+    //! rendering triangular mesh
+    QgsSymbol *mTriangularMeshSymbol = nullptr;
+};
+
+#endif //QGSMESHLAYER_H

src/core/mesh/qgsmeshlayerrenderer.cpp

@@ -0,0 +1,109 @@
+/***************************************************************************
+                         qgsmeshlayerrenderer.cpp
+                         ------------------------
+    begin                : April 2018
+    copyright            : (C) 2018 by Peter Petrik
+    email                : zilolv at gmail dot com
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgsmeshlayerrenderer.h"
+
+#include "qgsrenderer.h"
+#include "qgsrendercontext.h"
+#include "qgsmeshlayer.h"
+#include "qgsexception.h"
+#include "qgslogger.h"
+#include "qgssettings.h"
+#include "qgssinglesymbolrenderer.h"
+#include "qgsfield.h"
+#include "qgstriangularmesh.h"
+#include "qgspointxy.h"
+
+#include <QPicture>
+
+
+QgsMeshLayerRenderer::QgsMeshLayerRenderer( QgsMeshLayer *layer, QgsRenderContext &context )
+  : QgsMapLayerRenderer( layer->id() )
+  , mContext( context )
+{
+  // make copies for mesh data
+  Q_ASSERT( layer->nativeMesh() );
+  Q_ASSERT( layer->triangularMesh() );
+  mNativeMesh = *( layer->nativeMesh() );
+  mTriangularMesh = *( layer->triangularMesh() );
+
+  // make copies for symbols
+  if ( layer->nativeMeshSymbol() )
+  {
+    mNativeMeshSymbol = layer->nativeMeshSymbol()->clone();
+  }
+
+  if ( layer->triangularMeshSymbol() )
+  {
+    mTriangularMeshSymbol = layer->triangularMeshSymbol()->clone();
+  }
+}
+
+
+QgsMeshLayerRenderer::~QgsMeshLayerRenderer()
+{
+  if ( mNativeMeshSymbol )
+    delete mNativeMeshSymbol;
+
+  if ( mTriangularMeshSymbol )
+    delete mTriangularMeshSymbol;
+}
+
+
+
+bool QgsMeshLayerRenderer::render()
+{
+  renderMesh( mNativeMeshSymbol, mNativeMesh.faces ); // native mesh
+  renderMesh( mTriangularMeshSymbol, mTriangularMesh.triangles() ); // triangular mesh
+
+  return true;
+}
+
+void QgsMeshLayerRenderer::renderMesh( QgsSymbol *symbol, const QVector<QgsMeshFace> &faces )
+{
+  if ( !symbol )
+    return;
+
+  QgsFields fields;
+  QgsSingleSymbolRenderer renderer( symbol->clone() );
+  renderer.startRender( mContext, fields );
+
+  for ( int i = 0; i < faces.size(); ++i )
+  {
+    if ( mContext.renderingStopped() )
+      break;
+
+    const QgsMeshFace &face = faces[i];
+    QgsFeature feat;
+    feat.setFields( fields );
+    QVector<QgsPointXY> ring;
+    for ( int j = 0; j < face.size(); ++j )
+    {
+      int vertex_id = face[j];
+      Q_ASSERT( vertex_id < mTriangularMesh.vertices().size() ); //Triangular mesh vertices contains also native mesh vertices
+      const QgsPoint &vertex = mTriangularMesh.vertices()[vertex_id];
+      ring.append( vertex );
+    }
+    QgsPolygonXY polygon;
+    polygon.append( ring );
+    QgsGeometry geom = QgsGeometry::fromPolygonXY( polygon );
+    feat.setGeometry( geom );
+    renderer.renderFeature( feat, mContext );
+  }
+
+  renderer.stopRender( mContext );
+}

src/core/mesh/qgsmeshlayerrenderer.h

@@ -0,0 +1,79 @@
+/***************************************************************************
+                         qgsmeshlayerrenderer.h
+                         ----------------------
+    begin                : April 2018
+    copyright            : (C) 2018 by Peter Petrik
+    email                : zilolv at gmail dot com
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef QGSMESHLAYERRENDERER_H
+#define QGSMESHLAYERRENDERER_H
+
+class QgsRenderContext;
+class QgsMeshLayer;
+class QgsMeshVectorFieldRenderer;
+class QgsSingleSymbolRenderer;
+class QgsTriangularMesh;
+class QgsSymbol;
+
+#define SIP_NO_FILE
+
+#include <QList>
+#include <QPainter>
+
+#include "qgis.h"
+#include "qgsfeedback.h"
+
+#include "qgsmaplayerrenderer.h"
+#include "qgsmeshdataprovider.h"
+#include "qgstriangularmesh.h"
+
+/**
+ * \ingroup core
+ * Implementation of threaded rendering for mesh layers.
+ *
+ * \since QGIS 3.2
+ * \note not available in Python bindings
+ */
+class QgsMeshLayerRenderer : public QgsMapLayerRenderer
+{
+  public:
+    QgsMeshLayerRenderer( QgsMeshLayer *layer, QgsRenderContext &context );
+    ~QgsMeshLayerRenderer() override;
+
+    bool render() override;
+
+  private:
+    void renderMesh( QgsSymbol *symbol, const QVector<QgsMeshFace> &faces );
+
+
+  protected:
+    // copy from mesh layer
+    QgsMesh mNativeMesh;
+
+    // copy from mesh layer
+    QgsTriangularMesh mTriangularMesh;
+
+    // copy from mesh layer
+    QgsSymbol *mNativeMeshSymbol = nullptr;
+
+    // copy from mesh layer
+    QgsSymbol *mTriangularMeshSymbol = nullptr;
+
+    // rendering context
+    QgsRenderContext &mContext;
+
+
+};
+
+
+#endif // QGSMESHLAYERRENDERER_H

src/core/mesh/qgsmeshmemorydataprovider.cpp

@@ -0,0 +1,166 @@
+/***************************************************************************
+                         qgsmeshmemorydataprovider.cpp
+                         -----------------------------
+    begin                : April 2018
+    copyright            : (C) 2018 by Peter Petrik
+    email                : zilolv at gmail dot com
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgsmeshmemorydataprovider.h"
+#include <QFile>
+#include <QJsonDocument>
+#include <limits>
+
+static const QString TEXT_PROVIDER_KEY = QStringLiteral( "mesh_memory" );
+static const QString TEXT_PROVIDER_DESCRIPTION = QStringLiteral( "Mesh memory provider" );
+
+bool QgsMeshMemoryDataProvider::isValid() const
+{
+  return true;
+}
+
+QString QgsMeshMemoryDataProvider::name() const
+{
+  return "mesh_memory";
+}
+
+QString QgsMeshMemoryDataProvider::description() const
+{
+  return "memory data provider for mesh layer";
+}
+
+QgsCoordinateReferenceSystem QgsMeshMemoryDataProvider::crs() const
+{
+  return QgsCoordinateReferenceSystem();
+}
+
+QgsMeshMemoryDataProvider::QgsMeshMemoryDataProvider( const QString &uri )
+  : QgsMeshDataProvider( uri )
+  , mIsValid( false )
+{
+  mIsValid = splitSections( uri );
+}
+
+QgsMeshMemoryDataProvider::~QgsMeshMemoryDataProvider()
+{
+}
+
+QString QgsMeshMemoryDataProvider::providerKey()
+{
+  return TEXT_PROVIDER_KEY;
+}
+
+QString QgsMeshMemoryDataProvider::providerDescription()
+{
+  return TEXT_PROVIDER_DESCRIPTION;
+}
+
+QgsMeshMemoryDataProvider *QgsMeshMemoryDataProvider::createProvider( const QString &uri )
+{
+  return new QgsMeshMemoryDataProvider( uri );
+}
+
+bool QgsMeshMemoryDataProvider::splitSections( const QString &uri )
+{
+  QStringList sections = uri.split( "---", QString::SkipEmptyParts );
+  if ( sections.size() != 2 )
+  {
+    setError( QgsError( QStringLiteral( "Invalid mesh definition, does not contain 2 sections" ),
+                        QStringLiteral( "Mesh Memory Provider" ) ) );
+    return false;
+  }
+
+  if ( addVertices( sections[0] ) )
+    return addFaces( sections[1] );
+  else
+    return false;
+}
+
+bool QgsMeshMemoryDataProvider::addVertices( const QString &def )
+{
+  QVector<QgsMeshVertex> vertices;
+
+  QStringList verticesCoords = def.split( "\n", QString::SkipEmptyParts );
+  for ( int i = 0; i < verticesCoords.size(); ++i )
+  {
+    QStringList coords = verticesCoords[i].split( ",", QString::SkipEmptyParts );
+    if ( coords.size() != 2 )
+    {
+      setError( QgsError( QStringLiteral( "Invalid mesh definition, vertex definition does not contain x, y" ),
+                          QStringLiteral( "Mesh Memory Provider" ) ) );
+      return false;
+    }
+    double x = coords.at( 0 ).toDouble();
+    double y = coords.at( 1 ).toDouble();
+    QgsMeshVertex vertex( x, y );
+    vertices.push_back( vertex );
+  }
+
+  mVertices = vertices;
+  return true;
+}
+
+bool QgsMeshMemoryDataProvider::addFaces( const QString &def )
+{
+  QVector<QgsMeshFace> faces;
+
+  QStringList facesVertices = def.split( "\n", QString::SkipEmptyParts );
+  for ( int i = 0; i < facesVertices.size(); ++i )
+  {
+    QStringList vertices = facesVertices[i].split( ",", QString::SkipEmptyParts );
+    if ( vertices.size() < 3 )
+    {
+      setError( QgsError( QStringLiteral( "Invalid mesh definition, face must contain at least 3 vertices" ),
+                          QStringLiteral( "Mesh Memory Provider" ) ) );
+      return false;
+    }
+    QgsMeshFace face;
+    for ( int j = 0; j < vertices.size(); ++j )
+    {
+      int vertex_id = vertices[j].toInt();
+      face.push_back( vertex_id );
+      if ( face[j] >= mVertices.size() )
+      {
+        setError( QgsError( QStringLiteral( "Invalid mesh definition, missing vertex id defined in face" ),  QStringLiteral( "Mesh Memory Provider" ) ) );
+        return false;
+      }
+    }
+    faces.push_back( face );
+  }
+
+  mFaces = faces;
+  return true;
+}
+
+size_t QgsMeshMemoryDataProvider::vertexCount() const
+{
+  return mVertices.size();
+}
+
+size_t QgsMeshMemoryDataProvider::faceCount() const
+{
+  return mFaces.size();
+}
+
+QgsMeshVertex QgsMeshMemoryDataProvider::vertex( size_t index ) const
+{
+  Q_ASSERT( vertexCount() > index );
+  return mVertices[index];
+}
+
+QgsMeshFace QgsMeshMemoryDataProvider::face( size_t index ) const
+{
+  Q_ASSERT( faceCount() > index );
+  return mFaces[index];
+}
+
+

src/core/mesh/qgsmeshmemorydataprovider.h

@@ -0,0 +1,100 @@
+/***************************************************************************
+                         qgsmeshmemorydataprovider.h
+                         ---------------------------
+    begin                : April 2018
+    copyright            : (C) 2018 by Peter Petrik
+    email                : zilolv at gmail dot com
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef QGSMESHMEMORYDATAPROVIDER_H
+#define QGSMESHMEMORYDATAPROVIDER_H
+
+#define SIP_NO_FILE
+
+///@cond PRIVATE
+
+#include <cstddef>
+
+#include <QString>
+
+#include "qgis_core.h"
+#include "qgis.h"
+#include "qgsmeshdataprovider.h"
+#include "qgsrectangle.h"
+
+/**
+ * \ingroup core
+ * Provides data stored in-memory for QgsMeshLayer. Useful for plugins or tests.
+ * \since QGIS 3.2
+ */
+class QgsMeshMemoryDataProvider: public QgsMeshDataProvider
+{
+    Q_OBJECT
+
+  public:
+
+    /**
+     * Construct a mesh in-memory data provider from data string
+     *
+     * Data string constains simple definition of vertices and faces
+     * Each entry is separated by "\n" sign and section deliminer "---"
+     * vertex is x and y coordinate separated by comma
+     * face is list of vertex indexes, numbered from 0
+     * For example:
+     *
+     *  \code
+     *    QString uri(
+     *      "1.0, 2.0 \n" \
+     *      "2.0, 2.0 \n" \
+     *      "3.0, 2.0 \n" \
+     *      "2.0, 3.0 \n" \
+     *      "1.0, 3.0 \n" \
+     *      "---"
+     *      "0, 1, 3, 4 \n" \
+     *      "1, 2, 3 \n"
+     *    );
+     * \endcode
+     */
+    QgsMeshMemoryDataProvider( const QString &uri = QString() );
+    ~QgsMeshMemoryDataProvider();
+
+    bool isValid() const override;
+    QString name() const override;
+    QString description() const override;
+    QgsCoordinateReferenceSystem crs() const override;
+
+    size_t vertexCount() const override;
+    size_t faceCount() const override;
+    QgsMeshVertex vertex( size_t index ) const override;
+    QgsMeshFace face( size_t index ) const override;
+
+    //! Returns the memory provider key
+    static QString providerKey();
+    //! Returns the memory provider description
+    static QString providerDescription();
+    //! Provider factory
+    static QgsMeshMemoryDataProvider *createProvider( const QString &uri );
+  private:
+    bool splitSections( const QString &uri );
+
+    bool addVertices( const QString &def );
+    bool addFaces( const QString &def );
+
+    QVector<QgsMeshVertex> mVertices;
+    QVector<QgsMeshFace> mFaces;
+
+    bool mIsValid;
+};
+
+///@endcond
+
+#endif // QGSMESHMEMORYDATAPROVIDER_H

src/core/mesh/qgstriangularmesh.cpp

@@ -0,0 +1,110 @@
+/***************************************************************************
+                         qgstriangularmesh.cpp
+                         ---------------------
+    begin                : April 2018
+    copyright            : (C) 2018 by Peter Petrik
+    email                : zilolv at gmail dot com
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgstriangularmesh.h"
+#include "qgsmeshdataprovider.h"
+#include "qgsrendercontext.h"
+#include "qgscoordinatereferencesystem.h"
+#include "qgscoordinatetransform.h"
+#include "qgsmeshlayer.h"
+
+
+QgsTriangularMesh::QgsTriangularMesh( )
+{
+}
+
+QgsTriangularMesh::~QgsTriangularMesh()
+{
+}
+
+void QgsTriangularMesh::update( QgsMesh *nativeMesh, QgsRenderContext *context )
+{
+  Q_ASSERT( nativeMesh );
+  Q_ASSERT( context );
+
+  mTriangularMesh.vertices.clear();
+  mTriangularMesh.faces.clear();
+  mTrianglesToNativeFaces.clear();
+
+  // TRANSFORM VERTICES
+  QgsCoordinateTransform transform = context->coordinateTransform();
+  mTriangularMesh.vertices.resize( nativeMesh->vertices.size() );
+  for ( int i = 0; i < nativeMesh->vertices.size(); ++i )
+  {
+    QgsMeshVertex vertex = nativeMesh->vertices[i];
+    if ( transform.isValid() )
+    {
+      QgsPointXY mapPoint = transform.transform( QgsPointXY( vertex.x(), vertex.y() ) );
+      QgsMeshVertex mapVertex( mapPoint );
+      mapVertex.setZ( vertex.z() );
+      mapVertex.setM( vertex.m() );
+      mTriangularMesh.vertices[i] = mapVertex;
+    }
+    else
+    {
+      mTriangularMesh.vertices[i] = vertex;
+    }
+  }
+
+  // CREATE TRIANGULAR MESH
+  for ( int i = 0; i < nativeMesh->faces.size(); ++i )
+  {
+    QgsMeshFace face = nativeMesh->faces[i] ;
+    if ( face.size() == 3 )
+    {
+      // triangle
+      mTriangularMesh.faces.push_back( face );
+      mTrianglesToNativeFaces.push_back( i );
+    }
+    else if ( face.size() == 4 )
+    {
+      // quad
+      QgsMeshFace face1;
+      face1.push_back( face[0] );
+      face1.push_back( face[1] );
+      face1.push_back( face[2] );
+
+      mTriangularMesh.faces.push_back( face1 );
+      mTrianglesToNativeFaces.push_back( i );
+
+      QgsMeshFace face2;
+      face2.push_back( face[0] );
+      face2.push_back( face[2] );
+      face2.push_back( face[3] );
+
+      mTriangularMesh.faces.push_back( face2 );
+      mTrianglesToNativeFaces.push_back( i );
+    }
+  }
+
+}
+
+const QVector<QgsMeshVertex> &QgsTriangularMesh::vertices() const
+{
+  return mTriangularMesh.vertices;
+}
+
+const QVector<QgsMeshFace> &QgsTriangularMesh::triangles() const
+{
+  return mTriangularMesh.faces;
+}
+
+const QVector<int> &QgsTriangularMesh::trianglesToNativeFaces() const
+{
+  return mTrianglesToNativeFaces;
+}
+

src/core/mesh/qgstriangularmesh.h

@@ -0,0 +1,83 @@
+/***************************************************************************
+                         qgstriangularmesh.h
+                         -------------------
+    begin                : April 2018
+    copyright            : (C) 2018 by Peter Petrik
+    email                : zilolv at gmail dot com
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef QGSTRIANGULARMESH_H
+#define QGSTRIANGULARMESH_H
+
+
+#define SIP_NO_FILE
+
+#include <QList>
+#include <QPainter>
+#include <QVector>
+
+#include "qgis.h"
+#include "qgis_core.h"
+#include "qgsmeshdataprovider.h"
+#include "qgscoordinatereferencesystem.h"
+
+class QgsRenderContext;
+
+//! Mesh - vertices and faces
+struct CORE_EXPORT QgsMesh
+{
+  //! vertices
+  QVector<QgsMeshVertex> vertices;
+  //! faces
+  QVector<QgsMeshFace> faces;
+};
+
+/**
+ * Triangular/Derived Mesh
+ * \since QGIS 3.2
+ */
+class CORE_EXPORT QgsTriangularMesh
+{
+  public:
+    //! Ctor
+    QgsTriangularMesh();
+    //! Dtor
+    ~QgsTriangularMesh();
+
+    /**
+     * Construct triangular mesh from layer's native mesh and context
+     * \param layer QgsMeshLayer to get native mesh data
+     * \param context Rendering context to estimate number of triagles to create for an face
+    */
+    void update( QgsMesh *nativeMesh, QgsRenderContext *context );
+
+    /**
+     * Return vertices in map CRS
+     *
+     * The list of consist of vertices from native mesh (0-N) and
+     * extra vertices needed to create triangles (N+1 - len)
+     */
+    const QVector<QgsMeshVertex> &vertices() const ;
+    //! Return triangles
+    const QVector<QgsMeshFace> &triangles() const ;
+    //! Return mapping between triangles and original faces
+    const QVector<int> &trianglesToNativeFaces() const ;
+
+  private:
+    // vertices: map CRS; 0-N ... native vertices, N+1 - len ... extra vertices
+    // faces are derived triangles
+    QgsMesh mTriangularMesh;
+    QVector<int> mTrianglesToNativeFaces; //len(mTrianglesToNativeFaces) == len(mTriangles). Mapping derived -> native
+};
+
+
+#endif // QGSTRIANGULARMESH_H

src/core/processing/qgsprocessingutils.cpp

@@ -111,6 +111,8 @@ QgsMapLayer *QgsProcessingUtils::mapLayerFromStore( const QString &string, QgsMa
         return !canUseLayer( qobject_cast< QgsRasterLayer * >( layer ) );
       case QgsMapLayer::PluginLayer:
         return true;
+      case QgsMapLayer::MeshLayer:
+        return false;
     }
     return true;
   } ), layers.end() );

src/core/qgsdataitem.cpp

@@ -74,6 +74,12 @@ QIcon QgsLayerItem::iconRaster()
   return QgsApplication::getThemeIcon( QStringLiteral( "/mIconRaster.svg" ) );
 }
 
+QIcon QgsLayerItem::iconMesh()
+{
+  // TODO new icon!
+  return QgsApplication::getThemeIcon( QStringLiteral( "/mIconPointLayer.svg" ) );
+}
+
 QIcon QgsLayerItem::iconDefault()
 {
   return QgsApplication::getThemeIcon( QStringLiteral( "/mIconLayer.png" ) );
@@ -602,6 +608,8 @@ QgsMapLayer::LayerType QgsLayerItem::mapLayerType() const
 {
   if ( mLayerType == QgsLayerItem::Raster )
     return QgsMapLayer::RasterLayer;
+  if ( mLayerType == QgsLayerItem::Mesh )
+    return QgsMapLayer::MeshLayer;
   if ( mLayerType == QgsLayerItem::Plugin )
     return QgsMapLayer::PluginLayer;
   return QgsMapLayer::VectorLayer;
@@ -637,6 +645,8 @@ QString QgsLayerItem::iconName( QgsLayerItem::LayerType layerType )
     case Raster:
       return QStringLiteral( "/mIconRaster.svg" );
       break;
+    case Mesh:
+    //TODO add icon!
     default:
       return QStringLiteral( "/mIconLayer.png" );
       break;
@@ -670,6 +680,9 @@ QgsMimeDataUtils::Uri QgsLayerItem::mimeUri() const
     case QgsMapLayer::RasterLayer:
       u.layerType = QStringLiteral( "raster" );
       break;
+    case QgsMapLayer::MeshLayer:
+      u.layerType = QStringLiteral( "mesh" );
+      break;
     case QgsMapLayer::PluginLayer:
       u.layerType = QStringLiteral( "plugin" );
       break;

src/core/qgsdataitem.h

@@ -422,7 +422,8 @@ class CORE_EXPORT QgsLayerItem : public QgsDataItem
       TableLayer,
       Database,
       Table,
-      Plugin     //!< Added in 2.10
+      Plugin,    //!< Added in 2.10
+      Mesh       //!< Added in 3.2
     };
 
     Q_ENUM( LayerType );
@@ -498,6 +499,7 @@ class CORE_EXPORT QgsLayerItem : public QgsDataItem
     static QIcon iconTable();
     static QIcon iconRaster();
     static QIcon iconDefault();
+    static QIcon iconMesh();
 
     //! \returns the layer name
     virtual QString layerName() const { return name(); }

src/core/qgsdataprovider.h

@@ -59,6 +59,10 @@ class CORE_EXPORT QgsDataProvider : public QObject
     {
       sipType = sipType_QgsRasterDataProvider;
     }
+    else if ( qobject_cast<QgsMeshDataProvider *>( sipCpp ) )
+    {
+      sipType = sipType_QgsMeshDataProvider;
+    }
     else
     {
       sipType = 0;

src/core/qgsmaplayer.h

@@ -85,6 +85,9 @@ class CORE_EXPORT QgsMapLayer : public QObject
         case QgsMapLayer::PluginLayer:
           sipType = sipType_QgsPluginLayer;
           break;
+        case QgsMapLayer::MeshLayer:
+          sipType = sipType_QgsMeshLayer;
+          break;
         default:
           sipType = nullptr;
           break;
@@ -100,7 +103,8 @@ class CORE_EXPORT QgsMapLayer : public QObject
     {
       VectorLayer,
       RasterLayer,
-      PluginLayer
+      PluginLayer,
+      MeshLayer      //!< Added in 3.2
     };
 
     /**

src/core/qgsmaplayermodel.cpp

@@ -359,6 +359,11 @@ QIcon QgsMapLayerModel::iconForLayer( QgsMapLayer *layer )
       return QgsLayerItem::iconRaster();
     }
 
+    case QgsMapLayer::MeshLayer:
+    {
+      return QgsLayerItem::iconMesh();
+    }
+
     case QgsMapLayer::VectorLayer:
     {
       QgsVectorLayer *vl = dynamic_cast<QgsVectorLayer *>( layer );

src/core/qgsmimedatautils.cpp

@@ -24,6 +24,7 @@
 #include "qgsrasterlayer.h"
 #include "qgsvectordataprovider.h"
 #include "qgsvectorlayer.h"
+#include "qgsmeshlayer.h"
 
 static const char *QGIS_URILIST_MIMETYPE = "application/x-vnd.qgis.qgis.uri";
 
@@ -108,6 +109,18 @@ QgsRasterLayer *QgsMimeDataUtils::Uri::rasterLayer( bool &owner, QString &error
   return new QgsRasterLayer( uri, name, providerKey );
 }
 
+QgsMeshLayer *QgsMimeDataUtils::Uri::meshLayer( bool &owner, QString &error ) const
+{
+  owner = false;
+  if ( layerType != QLatin1String( "mesh" ) )
+  {
+    error = QObject::tr( "%1: Not a mesh layer." ).arg( name );
+    return nullptr;
+  }
+  owner = true;
+  return new QgsMeshLayer( uri, name, providerKey );
+}
+
 // -----
 
 bool QgsMimeDataUtils::isUriList( const QMimeData *data )

src/core/qgsmimedatautils.h

@@ -24,6 +24,7 @@ class QgsLayerItem;
 class QgsLayerTreeNode;
 class QgsVectorLayer;
 class QgsRasterLayer;
+class QgsMeshLayer;
 
 /**
  * \ingroup core
@@ -63,7 +64,14 @@ class CORE_EXPORT QgsMimeDataUtils
        */
       QgsRasterLayer *rasterLayer( bool &owner, QString &error ) const;
 
-      //! Type of URI. Recognized types: "vector" / "raster" / "plugin" / "custom" / "project"
+      /**
+       * Get mesh layer from uri if possible, otherwise returns 0 and error is set
+       * \param owner set to true if caller becomes owner
+       * \param error set to error message if cannot get raster
+       */
+      QgsMeshLayer *meshLayer( bool &owner, QString &error ) const;
+
+      //! Type of URI. Recognized types: "vector" / "raster" / "mesh" / "plugin" / "custom" / "project"
       QString layerType;
 
       /**

src/core/qgsproviderregistry.cpp

@@ -31,7 +31,7 @@
 #include "qgsvectorlayer.h"
 #include "qgsproject.h"
 #include "providers/memory/qgsmemoryprovider.h"
-
+#include "mesh/qgsmeshmemorydataprovider.h"
 
 // typedefs for provider plugin functions of interest
 typedef QString providerkey_t();
@@ -87,6 +87,7 @@ void QgsProviderRegistry::init()
 {
   // add standard providers
   mProviders[ QgsMemoryProvider::providerKey() ] = new QgsProviderMetadata( QgsMemoryProvider::providerKey(), QgsMemoryProvider::providerDescription(), &QgsMemoryProvider::createProvider );
+  mProviders[ QgsMeshMemoryDataProvider::providerKey() ] = new QgsProviderMetadata( QgsMeshMemoryDataProvider::providerKey(), QgsMeshMemoryDataProvider::providerDescription(), &QgsMeshMemoryDataProvider::createProvider );
 
   mLibraryDirectory.setSorting( QDir::Name | QDir::IgnoreCase );
   mLibraryDirectory.setFilter( QDir::Files | QDir::NoSymLinks );

src/core/qgsproviderregistry.h

@@ -167,6 +167,7 @@ class CORE_EXPORT QgsProviderRegistry
       \note This replaces QgsRasterLayer::buildSupportedRasterFileFilter()
      */
     virtual QString fileRasterFilters() const;
+
     //! Return a string containing the available database drivers
     virtual QString databaseDrivers() const;
     //! Return a string containing the available directory drivers

src/gui/CMakeLists.txt

@@ -890,6 +890,7 @@ INCLUDE_DIRECTORIES(
   ${CMAKE_SOURCE_DIR}/src/core/locator
   ${CMAKE_SOURCE_DIR}/src/core/metadata
   ${CMAKE_SOURCE_DIR}/src/core/processing
+  ${CMAKE_SOURCE_DIR}/src/core/mesh
   ${CMAKE_SOURCE_DIR}/src/core/providers/memory
   ${CMAKE_SOURCE_DIR}/src/core/raster
   ${CMAKE_SOURCE_DIR}/src/core/scalebar

src/gui/qgsbrowserdockwidget_p.cpp

@@ -35,7 +35,7 @@
 #include "qgsvectorlayer.h"
 #include "qgsproject.h"
 #include "qgssettings.h"
-
+#include "qgsmeshlayer.h"
 
 #include <QDragEnterEvent>
 
@@ -154,6 +154,20 @@ void QgsBrowserLayerProperties::setItem( QgsDataItem *item )
       delete layer;
     }
   }
+  else if ( type == QgsMapLayer::MeshLayer )
+  {
+    QgsDebugMsg( "creating mesh layer" );
+    QgsMeshLayer *layer = new QgsMeshLayer( layerItem->uri(), layerItem->uri(), layerItem->providerKey() );
+    if ( layer )
+    {
+      if ( layer->isValid() )
+      {
+        layerCrs = layer->crs();
+        layerMetadata = layer->htmlMetadata();
+      }
+      delete layer;
+    }
+  }
   else if ( type == QgsMapLayer::VectorLayer )
   {
     QgsDebugMsg( "creating vector layer" );

src/providers/CMakeLists.txt

@@ -16,6 +16,7 @@ ADD_SUBDIRECTORY(wfs)
 ADD_SUBDIRECTORY(spatialite)
 ADD_SUBDIRECTORY(virtual)
 ADD_SUBDIRECTORY(db2)
+ADD_SUBDIRECTORY(mdal)
 
 IF (WITH_ORACLE)
   ADD_SUBDIRECTORY(oracle)

src/providers/mdal/CMakeLists.txt

@@ -0,0 +1,80 @@
+SET(MDAL_SRCS
+  qgsmdalprovider.cpp
+  qgsmdaldataitems.cpp
+)
+SET(MDAL_MOC_HDRS
+  qgsmdalprovider.h
+  qgsmdaldataitems.h
+)
+SET(MDAL_HDRS
+)
+
+
+########################################################
+# Compile internal MDAL
+IF (WITH_INTERNAL_MDAL)
+  ADD_DEFINITIONS(-DMDAL_STATIC)
+
+  INCLUDE_DIRECTORIES(
+    ${CMAKE_SOURCE_DIR}/external/mdal
+    ${CMAKE_SOURCE_DIR}/external/mdal/api
+  )
+
+  SET(MDAL_LIB_SRCS
+    ${CMAKE_SOURCE_DIR}/external/mdal/mdal.cpp
+    ${CMAKE_SOURCE_DIR}/external/mdal/mdal_utils.cpp
+    ${CMAKE_SOURCE_DIR}/external/mdal/mdal_loader.cpp
+    ${CMAKE_SOURCE_DIR}/external/mdal/frmts/mdal_2dm.cpp
+  )
+
+  SET(MDAL_LIB_HDRS
+    ${CMAKE_SOURCE_DIR}/external/mdal/api/mdal.h
+    ${CMAKE_SOURCE_DIR}/external/mdal/mdal_utils.hpp
+    ${CMAKE_SOURCE_DIR}/external/mdal/mdal_loader.hpp
+    ${CMAKE_SOURCE_DIR}/external/mdal/mdal_defines.hpp
+    ${CMAKE_SOURCE_DIR}/external/mdal/frmts/mdal_2dm.hpp
+  )
+
+  UNSET(MDAL_LIBRARY)
+  UNSET(MDAL_INCLUDE_DIR)
+
+ELSE (WITH_INTERNAL_MDAL)
+
+  INCLUDE_DIRECTORIES (SYSTEM
+    ${MDAL_INCLUDE_DIR}
+  )
+
+ENDIF (WITH_INTERNAL_MDAL)
+
+########################################################
+
+INCLUDE_DIRECTORIES (
+  ${CMAKE_SOURCE_DIR}/src/core
+  ${CMAKE_SOURCE_DIR}/src/core/mesh
+  ${CMAKE_SOURCE_DIR}/src/core/expression
+  ${CMAKE_SOURCE_DIR}/src/core/geometry
+  ${CMAKE_SOURCE_DIR}/src/core/metadata
+
+  ${CMAKE_BINARY_DIR}/src/core
+)
+
+QT5_WRAP_CPP(MDAL_MOC_SRCS ${MDAL_MOC_HDRS})
+ADD_LIBRARY (mdalprovider MODULE ${MDAL_SRCS} ${MDAL_MOC_HDRS} ${MDAL_MOC_SRCS} ${MDAL_LIB_SRCS} ${MDAL_LIB_HDRS})
+
+TARGET_LINK_LIBRARIES (mdalprovider
+  qgis_core
+  ${MDAL_LIBRARY}
+)
+
+# clang-tidy
+IF(CLANG_TIDY_EXE)
+  SET_TARGET_PROPERTIES(
+    mdalprovider PROPERTIES
+    CXX_CLANG_TIDY "${DO_CLANG_TIDY}"
+  )
+ENDIF(CLANG_TIDY_EXE)
+
+INSTALL(TARGETS mdalprovider
+  RUNTIME DESTINATION ${QGIS_PLUGIN_DIR}
+  LIBRARY DESTINATION ${QGIS_PLUGIN_DIR})
+

src/providers/mdal/qgsmdaldataitems.cpp

@@ -0,0 +1,76 @@
+/***************************************************************************
+    qgsmdaldataitems.cpp
+    ---------------------
+    begin                : April 2018
+    copyright            : (C) 2018 by Peter Petrik
+    email                : zilolv at gmail dot com
+ ***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+#include "qgsmdaldataitems.h"
+#include "qgsmdalprovider.h"
+#include "qgslogger.h"
+#include "qgssettings.h"
+
+#include <QFileInfo>
+
+
+QgsMdalLayerItem::QgsMdalLayerItem( QgsDataItem *parent,
+                                    const QString &name, const QString &path, const QString &uri )
+  : QgsLayerItem( parent, name, path, uri, QgsLayerItem::Mesh, QStringLiteral( "mdal" ) )
+{
+  mToolTip = uri;
+  setState( Populated );
+}
+
+QString QgsMdalLayerItem::layerName() const
+{
+  QFileInfo info( name() );
+  return info.completeBaseName();
+}
+
+// ---------------------------------------------------------------------------
+static QStringList sExtensions = QStringList();
+
+QGISEXTERN int dataCapabilities()
+{
+  return QgsDataProvider::File;
+}
+
+QGISEXTERN QgsDataItem *dataItem( QString path, QgsDataItem *parentItem )
+{
+  if ( path.isEmpty() )
+    return nullptr;
+
+  QgsDebugMsgLevel( "thePath = " + path, 2 );
+
+  // get suffix, removing .gz if present
+  QFileInfo info( path );
+  QString suffix = info.suffix().toLower();
+  // extract basename with extension
+  info.setFile( path );
+  QString name = info.fileName();
+
+  // allow only normal files
+  if ( !info.isFile() )
+    return nullptr;
+
+  // get supported extensions
+  if ( sExtensions.isEmpty() )
+  {
+    // TODO ask MDAL for extensions !
+    sExtensions << QStringLiteral( "2dm" );
+  }
+
+  // Filter files by extension
+  if ( !sExtensions.contains( suffix ) )
+    return nullptr;
+
+  return new QgsMdalLayerItem( parentItem, name, path, path );
+}
+

src/providers/mdal/qgsmdaldataitems.h

@@ -0,0 +1,29 @@
+/***************************************************************************
+    qgsmdaldataitems.h
+    ------------------
+    begin                : April 2018
+    copyright            : (C) 2018 by Peter Petrik
+    email                : zilolv at gmail dot com
+ ***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+#ifndef QGSMDALDATAITEMS_H
+#define QGSMDALDATAITEMS_H
+
+#include "qgsdataitem.h"
+
+class QgsMdalLayerItem : public QgsLayerItem
+{
+    Q_OBJECT
+  public:
+    QgsMdalLayerItem( QgsDataItem *parent, const QString &name, const QString &path, const QString &uri );
+
+    QString layerName() const override;
+};
+
+#endif // QGSMDALDATAITEMS_H

src/providers/mdal/qgsmdalprovider.cpp

@@ -0,0 +1,137 @@
+/***************************************************************************
+                         qgsmeshmemorydataprovider.cpp
+                         -----------------------------
+    begin                : April 2018
+    copyright            : (C) 2018 by Peter Petrik
+    email                : zilolv at gmail dot com
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgsmdalprovider.h"
+#include <QFile>
+#include <QJsonDocument>
+#include <limits>
+#include "mdal.h"
+
+static const QString TEXT_PROVIDER_KEY = QStringLiteral( "mdal" );
+static const QString TEXT_PROVIDER_DESCRIPTION = QStringLiteral( "MDAL provider" );
+
+bool QgsMdalProvider::isValid() const
+{
+  return mMeshH != nullptr;
+}
+
+QString QgsMdalProvider::name() const
+{
+  return TEXT_PROVIDER_KEY;
+}
+
+QString QgsMdalProvider::description() const
+{
+  return TEXT_PROVIDER_DESCRIPTION;
+}
+
+QgsCoordinateReferenceSystem QgsMdalProvider::crs() const
+{
+  return QgsCoordinateReferenceSystem();
+}
+
+QgsMdalProvider::QgsMdalProvider( const QString &uri )
+  : QgsMeshDataProvider( uri )
+{
+  QByteArray curi = uri.toAscii();
+  mMeshH = MDAL_LoadMesh( curi.constData() );
+}
+
+QgsMdalProvider::~QgsMdalProvider()
+{
+  if ( mMeshH )
+    MDAL_CloseMesh( mMeshH );
+}
+
+size_t QgsMdalProvider::vertexCount() const
+{
+  if ( mMeshH )
+    return MDAL_M_vertexCount( mMeshH );
+  else
+    return ( size_t ) 0;
+}
+
+size_t QgsMdalProvider::faceCount() const
+{
+  if ( mMeshH )
+    return MDAL_M_faceCount( mMeshH );
+  else
+    return ( size_t ) 0;
+}
+
+QgsMeshVertex QgsMdalProvider::vertex( size_t index ) const
+{
+  Q_ASSERT( index < vertexCount() );
+  double x = MDAL_M_vertexXCoordinatesAt( mMeshH, index );
+  double y = MDAL_M_vertexYCoordinatesAt( mMeshH, index );
+  QgsMeshVertex vertex( x, y );
+  return vertex;
+}
+
+QgsMeshFace QgsMdalProvider::face( size_t index ) const
+{
+  Q_ASSERT( index < faceCount() );
+  QgsMeshFace face;
+  int n_face_vertices = MDAL_M_faceVerticesCountAt( mMeshH, index );
+  for ( size_t j = 0; j < n_face_vertices; ++j )
+  {
+    int vertex_index = MDAL_M_faceVerticesIndexAt( mMeshH, index, j );
+    face.push_back( vertex_index );
+  }
+  return face;
+}
+
+/*----------------------------------------------------------------------------------------------*/
+
+/**
+ * Class factory to return a pointer to a newly created
+ * QgsGdalProvider object
+ */
+QGISEXTERN QgsMdalProvider *classFactory( const QString *uri )
+{
+  return new QgsMdalProvider( *uri );
+}
+
+/**
+ * Required key function (used to map the plugin to a data store type)
+*/
+QGISEXTERN QString providerKey()
+{
+  return TEXT_PROVIDER_KEY;
+}
+
+/**
+ * Required description function
+ */
+QGISEXTERN QString description()
+{
+  return TEXT_PROVIDER_DESCRIPTION;
+}
+
+/**
+ * Required isProvider function. Used to determine if this shared library
+ * is a data provider plugin
+ */
+QGISEXTERN bool isProvider()
+{
+  return true;
+}
+
+QGISEXTERN void cleanupProvider()
+{
+}
+

src/providers/mdal/qgsmdalprovider.h

@@ -0,0 +1,71 @@
+/***************************************************************************
+    qgsmdalprovider.h
+    -----------------
+    begin                : April 2018
+    copyright            : (C) 2018 by Peter Petrik
+    email                : zilolv at gmail dot com
+ ***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef QGSMDALPROVIDER_H
+#define QGSGDALPROVIDER_H
+
+#include <cstddef>
+
+#include "qgscoordinatereferencesystem.h"
+#include "qgsdataitem.h"
+#include "qgsmeshdataprovider.h"
+#include "qgsrectangle.h"
+
+#include <QString>
+#include <QStringList>
+#include <QDomElement>
+#include <QMap>
+#include <QVector>
+
+#include <mdal.h>
+
+class QMutex;
+class QgsCoordinateTransform;
+
+/**
+  \brief Data provider for MDAL layers.
+*/
+class QgsMdalProvider : public QgsMeshDataProvider
+{
+    Q_OBJECT
+
+  public:
+
+    /**
+     * Constructor for the provider.
+     *
+     * \param   uri         file name
+     * \param   newDataset  handle of newly created dataset.
+     *
+     */
+    QgsMdalProvider( const QString &uri = QString() );
+    ~QgsMdalProvider();
+
+    bool isValid() const override;
+    QString name() const override;
+    QString description() const override;
+    QgsCoordinateReferenceSystem crs() const override;
+
+    size_t vertexCount() const override;
+    size_t faceCount() const override;
+    QgsMeshVertex vertex( size_t index ) const override;
+    QgsMeshFace face( size_t index ) const override;
+
+  private:
+    MeshH mMeshH;
+};
+
+#endif
+

src/providers/ogr/qgsgeopackagedataitems.cpp

@@ -228,6 +228,12 @@ bool QgsGeoPackageCollectionItem::handleDrop( const QMimeData *data, Qt::DropAct
         srcLayer = dropUri.vectorLayer( owner, error );
         isVector = true;
       }
+      else if ( dropUri.layerType == QStringLiteral( "mesh" ) )
+      {
+        // unsuported
+        hasError = true;
+        continue;
+      }
       else
       {
         srcLayer = dropUri.rasterLayer( owner, error );

tests/src/core/CMakeLists.txt

@@ -20,6 +20,7 @@ INCLUDE_DIRECTORIES(${CMAKE_CURRENT_SOURCE_DIR}
   ${CMAKE_SOURCE_DIR}/src/core/raster
   ${CMAKE_SOURCE_DIR}/src/core/scalebar
   ${CMAKE_SOURCE_DIR}/src/core/symbology
+  ${CMAKE_SOURCE_DIR}/src/core/mesh
   ${CMAKE_SOURCE_DIR}/src/test
   ${CMAKE_BINARY_DIR}/src/core
 )
@@ -186,7 +187,9 @@ SET(TESTS
  testqgsvectorlayerjoinbuffer.cpp
  testqgsvectorlayer.cpp
  testziplayer.cpp
-    )
+ testqgsmeshlayer.cpp
+ testqgsmeshlayerrenderer.cpp
+   )
 
 IF(WITH_QTWEBKIT)
   SET(TESTS ${TESTS}

tests/src/core/testqgsmeshlayer.cpp

@@ -0,0 +1,132 @@
+/***************************************************************************
+                         testqgsmeshlayer.cpp
+                         --------------------
+    begin                : April 2018
+    copyright            : (C) 2018 by Peter Petrik
+    email                : zilolv at gmail dot com
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgstest.h"
+#include <QObject>
+#include <QString>
+#include <QLabel>
+#include <QStringList>
+#include <QApplication>
+#include <QFileInfo>
+#include <QDir>
+#include <QDesktopServices>
+
+//qgis includes...
+#include "qgsmaplayer.h"
+#include "qgsmeshlayer.h"
+#include "qgsapplication.h"
+#include "qgsproviderregistry.h"
+#include "qgsproject.h"
+#include "qgsmaprenderersequentialjob.h"
+#include "qgsmeshmemorydataprovider.h"
+
+/**
+ * \ingroup UnitTests
+ * This is a unit test for a mesh layer
+ */
+class TestQgsMeshLayer : public QObject
+{
+    Q_OBJECT
+
+  public:
+    TestQgsMeshLayer() = default;
+
+  private:
+    QgsMeshLayer *mMemoryLayer = nullptr;
+    QgsMeshLayer *mMdalLayer = nullptr;
+
+  private slots:
+    void initTestCase();// will be called before the first testfunction is executed.
+    void cleanupTestCase();// will be called after the last testfunction was executed.
+    void init() {} // will be called before each testfunction is executed.
+    void cleanup() {} // will be called after every testfunction.
+
+    void test_data_provider();
+    void test_extent();
+};
+
+void TestQgsMeshLayer::initTestCase()
+{
+  // init QGIS's paths - true means that all path will be inited from prefix
+  QgsApplication::init();
+  QgsApplication::initQgis();
+  QgsApplication::showSettings();
+  QString myDataDir( TEST_DATA_DIR ); //defined in CmakeLists.txt
+  myDataDir += "/mesh";
+  // Memory layer
+  QFile f( myDataDir + "/quad_and_triangle.txt" );
+  QVERIFY( f.open( QIODevice::ReadOnly | QIODevice::Text ) );
+  QString uri( f.readAll() );
+  QVERIFY( !uri.isEmpty() );
+  mMemoryLayer = new QgsMeshLayer( uri, "Triangle and Quad Memory", "mesh_memory" );
+  QVERIFY( mMemoryLayer->isValid() );
+  QgsProject::instance()->addMapLayers(
+    QList<QgsMapLayer *>() << mMemoryLayer );
+
+  // MDAL Layer
+  uri = myDataDir + "/quad_and_triangle.2dm";
+  mMdalLayer = new QgsMeshLayer( uri, "Triangle and Quad MDAL", "mdal" );
+  QVERIFY( mMdalLayer->isValid() );
+  QgsProject::instance()->addMapLayers(
+    QList<QgsMapLayer *>() << mMdalLayer );
+}
+
+void TestQgsMeshLayer::cleanupTestCase()
+{
+  QgsApplication::exitQgis();
+}
+
+void TestQgsMeshLayer::test_data_provider()
+{
+  QList<const QgsMeshDataProvider *> dataProviders;
+  dataProviders.append( mMemoryLayer->dataProvider() );
+  dataProviders.append( mMdalLayer->dataProvider() );
+
+  QgsRectangle expectedExtent( 1000.0, 2000.0, 3000.0, 3000.0 );
+
+  foreach ( auto dp, dataProviders )
+  {
+    QVERIFY( dp != nullptr );
+    QVERIFY( dp->isValid() );
+    QCOMPARE( expectedExtent, dp->extent() );
+
+    QCOMPARE( ( size_t ) 5, dp->vertexCount() );
+    QCOMPARE( QgsMeshVertex( 1000.0, 2000.0 ), dp->vertex( 0 ) );
+    QCOMPARE( QgsMeshVertex( 2000.0, 2000.0 ), dp->vertex( 1 ) );
+    QCOMPARE( QgsMeshVertex( 3000.0, 2000.0 ), dp->vertex( 2 ) );
+    QCOMPARE( QgsMeshVertex( 2000.0, 3000.0 ), dp->vertex( 3 ) );
+    QCOMPARE( QgsMeshVertex( 1000.0, 3000.0 ), dp->vertex( 4 ) );
+
+    QCOMPARE( ( size_t ) 2, dp->faceCount() );
+    QgsMeshFace f1;
+    f1 << 0 << 1 << 3 << 4;
+    QCOMPARE( f1, dp->face( 0 ) );
+
+    QgsMeshFace f2;
+    f2 << 1 << 2 << 3;
+    QCOMPARE( f2, dp->face( 1 ) );
+  }
+}
+
+void TestQgsMeshLayer::test_extent()
+{
+  QCOMPARE( mMemoryLayer->dataProvider()->extent(), mMemoryLayer->extent() );
+  QCOMPARE( mMdalLayer->dataProvider()->extent(), mMdalLayer->extent() );
+}
+
+QGSTEST_MAIN( TestQgsMeshLayer )
+#include "testqgsmeshlayer.moc"

tests/src/core/testqgsmeshlayerrenderer.cpp

@@ -0,0 +1,123 @@
+/***************************************************************************
+                         testqgsmeshlayer.cpp
+                         --------------------
+    begin                : April 2018
+    copyright            : (C) 2018 by Peter Petrik
+    email                : zilolv at gmail dot com
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgstest.h"
+#include <QObject>
+#include <QString>
+#include <QLabel>
+#include <QStringList>
+#include <QApplication>
+#include <QFileInfo>
+#include <QDir>
+#include <QDesktopServices>
+
+//qgis includes...
+#include "qgsmaplayer.h"
+#include "qgsmeshlayer.h"
+#include "qgsapplication.h"
+#include "qgsproviderregistry.h"
+#include "qgsproject.h"
+#include "qgsmaprenderersequentialjob.h"
+#include "qgsmeshmemorydataprovider.h"
+
+//qgis test includes
+#include "qgsrenderchecker.h"
+
+/**
+ * \ingroup UnitTests
+ * This is a unit test for the different renderers for mesh layers.
+ */
+class TestQgsMeshRenderer : public QObject
+{
+    Q_OBJECT
+
+  public:
+    TestQgsMeshRenderer() = default;
+
+  private:
+    QgsMeshLayer *mMemoryLayer = nullptr;
+    QgsMapSettings *mMapSettings = nullptr;
+
+  private slots:
+    void initTestCase();// will be called before the first testfunction is executed.
+    void cleanupTestCase();// will be called after the last testfunction was executed.
+    void init() {} // will be called before each testfunction is executed.
+    void cleanup() {} // will be called after every testfunction.
+    bool imageCheck( const QString &testType );
+
+    void test_native_mesh_rendering();
+    void test_triangular_mesh_rendering();
+};
+
+void TestQgsMeshRenderer::initTestCase()
+{
+  // init QGIS's paths - true means that all path will be inited from prefix
+  QgsApplication::init();
+  QgsApplication::initQgis();
+  QgsApplication::showSettings();
+  QString myDataDir( TEST_DATA_DIR ); //defined in CmakeLists.txt
+  myDataDir += "/mesh";
+
+  mMapSettings = new QgsMapSettings();
+
+  // Memory layer
+  QFile f( myDataDir + "/quad_and_triangle.txt" );
+  QVERIFY( f.open( QIODevice::ReadOnly | QIODevice::Text ) );
+  QString uri( f.readAll() );
+  QVERIFY( !uri.isEmpty() );
+  mMemoryLayer = new QgsMeshLayer( uri, "Triangle and Quad Memory", "mesh_memory" );
+  QVERIFY( mMemoryLayer->isValid() );
+  QgsProject::instance()->addMapLayers(
+    QList<QgsMapLayer *>() << mMemoryLayer );
+  mMapSettings->setLayers(
+    QList<QgsMapLayer *>() << mMemoryLayer );
+}
+void TestQgsMeshRenderer::cleanupTestCase()
+{
+  QgsApplication::exitQgis();
+}
+
+bool TestQgsMeshRenderer::imageCheck( const QString &testType )
+{
+  mMapSettings->setExtent( mMemoryLayer->extent() );
+  mMapSettings->setDestinationCrs( mMemoryLayer->crs() );
+  mMapSettings->setOutputDpi( 96 );
+  QgsRenderChecker myChecker;
+  myChecker.setControlPathPrefix( QStringLiteral( "mesh" ) );
+  myChecker.setControlName( "expected_" + testType );
+  myChecker.setMapSettings( *mMapSettings );
+  myChecker.setColorTolerance( 15 );
+  bool myResultFlag = myChecker.runTest( testType, 0 );
+  return myResultFlag;
+}
+
+void TestQgsMeshRenderer::test_native_mesh_rendering()
+{
+  mMemoryLayer->toggleTriangularMeshRendering( false );
+  QVERIFY( mMemoryLayer->triangularMeshSymbol() == nullptr );
+  QVERIFY( imageCheck( "quad_and_triangle_native_mesh" ) );
+}
+
+void TestQgsMeshRenderer::test_triangular_mesh_rendering()
+{
+  mMemoryLayer->toggleTriangularMeshRendering( true );
+  QVERIFY( mMemoryLayer->triangularMeshSymbol() != nullptr );
+  QVERIFY( imageCheck( "quad_and_triangle_triangular_mesh" ) );
+}
+
+QGSTEST_MAIN( TestQgsMeshRenderer )
+#include "testqgsmeshlayerrenderer.moc"

tests/testdata/mesh/quad_and_triangle.2dm

@@ -0,0 +1,8 @@
+MESH2D      1000.000      2000.000    0.000000     200     300  1.000  1.000
+ND         1      1000.000      2000.000      20.000
+ND         2      2000.000      2000.000      30.000
+ND         3      3000.000      2000.000      40.000
+ND         4      2000.000      3000.000      50.000
+ND         5      1000.000      3000.000      10.000
+E4Q        1    1    2    4    5   1
+E3T        2    2    3    4    1

tests/testdata/mesh/quad_and_triangle.txt

@@ -0,0 +1,8 @@
+1000.0, 2000.0
+2000.0, 2000.0
+3000.0, 2000.0
+2000.0, 3000.0
+1000.0, 3000.0
+---
+0, 1, 3, 4
+1, 2, 3