qgsphongtexturedmaterialsettings: Add support for opacity

Qt3DRender::QTexture2D does not handle opacity. Therefore, it is not
possible to use the default Qt3DExtras::QDiffuseSpecularMaterial
implementation. This problem is solved by using
Qt3DRender::QMaterial and copying the
Qt3DExtras::QDiffuseSpecularMaterial shaders from Qt3D source
code. Then, the texture color needs to be changed to set the correct
opacity. This is achieved in the fragement shader:

```
vec4 diffuseTextureColor = vec4(texture(diffuseTexture, texCoord).rgb,
opacity);
```

instead of the default:

```
vec4 diffuseTextureColor = vec4(texture(diffuseTexture, texCoord));
```

As far as the FrameGraph is concerned, this is already handled in
Qgs3DMapScene::finalizeNewEntity which checks for all material which
have an effect with an opacity parameter.

python/3d/auto_generated/materials/qgsphongtexturedmaterialsettings.sip.in

@@ -88,6 +88,13 @@ during triangulation.quiresTextureCoordinates
     float textureRotation() const;
 %Docstring
 Returns the texture rotation, in degrees.
+%End
+
+    float opacity() const;
+%Docstring
+Returns the opacity of the surface
+
+.. versionadded:: 3.28
 %End
 
     void setAmbient( const QColor &ambient );
@@ -121,6 +128,13 @@ If the texture scale is less than 1 the texture will be stretched
     void setTextureRotation( float rotation );
 %Docstring
 Sets the texture rotation in degrees
+%End
+
+    void setOpacity( float opacity );
+%Docstring
+Sets opacity of the surface.
+
+.. versionadded:: 3.28
 %End
 
     virtual void readXml( const QDomElement &elem, const QgsReadWriteContext &context );

src/3d/materials/qgsphongtexturedmaterialsettings.cpp

@@ -20,11 +20,12 @@
 #include "qgsimagecache.h"
 #include "qgsimagetexture.h"
 #include "qgsphongmaterialsettings.h"
-#include <Qt3DExtras/QDiffuseSpecularMaterial>
 #include <Qt3DRender/QPaintedTextureImage>
 #include <Qt3DRender/QTexture>
 #include <Qt3DRender/QParameter>
 #include <Qt3DRender/QEffect>
+#include <Qt3DRender/QTechnique>
+#include <Qt3DRender/QGraphicsApiFilter>
 #include <QMap>
 
 
@@ -71,6 +72,7 @@ void QgsPhongTexturedMaterialSettings::readXml( const QDomElement &elem, const Q
   mAmbient = QgsSymbolLayerUtils::decodeColor( elem.attribute( QStringLiteral( "ambient" ), QStringLiteral( "25,25,25" ) ) );
   mSpecular = QgsSymbolLayerUtils::decodeColor( elem.attribute( QStringLiteral( "specular" ), QStringLiteral( "255,255,255" ) ) );
   mShininess = elem.attribute( QStringLiteral( "shininess" ) ).toFloat();
+  mOpacity = elem.attribute( QStringLiteral( "opacity" ), QStringLiteral( "1.0" ) ).toFloat();
   mDiffuseTexturePath = elem.attribute( QStringLiteral( "diffuse_texture_path" ), QString() );
   mTextureScale = elem.attribute( QStringLiteral( "texture_scale" ), QString( "1.0" ) ).toFloat();
   mTextureRotation = elem.attribute( QStringLiteral( "texture-rotation" ), QString( "0.0" ) ).toFloat();
@@ -83,6 +85,7 @@ void QgsPhongTexturedMaterialSettings::writeXml( QDomElement &elem, const QgsRea
   elem.setAttribute( QStringLiteral( "ambient" ), QgsSymbolLayerUtils::encodeColor( mAmbient ) );
   elem.setAttribute( QStringLiteral( "specular" ), QgsSymbolLayerUtils::encodeColor( mSpecular ) );
   elem.setAttribute( QStringLiteral( "shininess" ), mShininess );
+  elem.setAttribute( QStringLiteral( "opacity" ), mOpacity );
   elem.setAttribute( QStringLiteral( "diffuse_texture_path" ), mDiffuseTexturePath );
   elem.setAttribute( QStringLiteral( "texture_scale" ), mTextureScale );
   elem.setAttribute( QStringLiteral( "texture-rotation" ), mTextureRotation );
@@ -113,16 +116,50 @@ Qt3DRender::QMaterial *QgsPhongTexturedMaterialSettings::toMaterial( QgsMaterial
         QgsPhongMaterialSettings phongSettings = QgsPhongMaterialSettings();
         phongSettings.setAmbient( mAmbient );
         phongSettings.setDiffuse( QColor::fromRgbF( 0.7f, 0.7f, 0.7f, 1.0f ) ); // default diffuse color from QDiffuseSpecularMaterial
-        phongSettings.setOpacity( 1.0 ); // QgsPhongTexturedMaterialSettings does not handle opacity
+        phongSettings.setOpacity( mOpacity );
         phongSettings.setShininess( mShininess );
         phongSettings.setSpecular( mSpecular );
         Qt3DRender::QMaterial *material = phongSettings.toMaterial( technique, context );
         return material;
       }
 
-      QgsImageTexture *textureImage = new QgsImageTexture( textureSourceImage );
-      Qt3DExtras::QDiffuseSpecularMaterial *material = new Qt3DExtras::QDiffuseSpecularMaterial;
+      // Use a custom material because Qt3DRender::QTexture2D does not handle opacity.
+      Qt3DRender::QMaterial *material = new Qt3DRender::QMaterial;
 
+      Qt3DRender::QEffect *effect = new Qt3DRender::QEffect( material );
+
+      Qt3DRender::QTechnique *technique = new Qt3DRender::QTechnique;
+      technique->graphicsApiFilter()->setApi( Qt3DRender::QGraphicsApiFilter::OpenGL );
+      technique->graphicsApiFilter()->setProfile( Qt3DRender::QGraphicsApiFilter::CoreProfile );
+      technique->graphicsApiFilter()->setMajorVersion( 3 );
+      technique->graphicsApiFilter()->setMinorVersion( 3 );
+      Qt3DRender::QFilterKey *filterKey = new Qt3DRender::QFilterKey();
+      filterKey->setName( QStringLiteral( "renderingStyle" ) );
+      filterKey->setValue( QStringLiteral( "forward" ) );
+      technique->addFilterKey( filterKey );
+
+      Qt3DRender::QRenderPass *renderPass = new Qt3DRender::QRenderPass();
+      Qt3DRender::QShaderProgram *shaderProgram = new Qt3DRender::QShaderProgram();
+
+      //Load shader programs
+      const QUrl urlVert( QStringLiteral( "qrc:/shaders/diffuseSpecular.vert" ) );
+      shaderProgram->setShaderCode( Qt3DRender::QShaderProgram::Vertex, Qt3DRender::QShaderProgram::loadSource( urlVert ) );
+      const QUrl urlFrag( QStringLiteral( "qrc:/shaders/diffuseSpecular.frag" ) );
+      shaderProgram->setShaderCode( Qt3DRender::QShaderProgram::Fragment, Qt3DRender::QShaderProgram::loadSource( urlFrag ) );
+
+      renderPass->setShaderProgram( shaderProgram );
+      technique->addRenderPass( renderPass );
+
+      int opacity = mOpacity * 255;
+      QColor ambient = context.isSelected() ? context.selectionColor().darker() : mAmbient;
+      effect->addParameter( new Qt3DRender::QParameter( QStringLiteral( "ka" ), QColor( ambient.red(), ambient.green(), ambient.blue(), opacity ) ) );
+      effect->addParameter( new Qt3DRender::QParameter( QStringLiteral( "ks" ), QColor( mSpecular.red(), mSpecular.green(), mSpecular.blue(), opacity ) ) );
+      effect->addParameter( new Qt3DRender::QParameter( QStringLiteral( "shininess" ), mShininess ) );
+      effect->addParameter( new Qt3DRender::QParameter( QStringLiteral( "opacity" ), mOpacity ) );
+
+      // TODO : if ( context.isSelected() ) dampen the color of diffuse texture
+      // with context.map().selectionColor()
+      QgsImageTexture *textureImage = new QgsImageTexture( textureSourceImage );
       Qt3DRender::QTexture2D *texture = new Qt3DRender::QTexture2D();
       texture->addTextureImage( textureImage );
 
@@ -136,21 +173,11 @@ Qt3DRender::QMaterial *QgsPhongTexturedMaterialSettings::toMaterial( QgsMaterial
       texture->setMagnificationFilter( Qt3DRender::QTexture2D::Linear );
       texture->setMinificationFilter( Qt3DRender::QTexture2D::Linear );
 
-      material->setDiffuse( QVariant::fromValue( texture ) );
-
-      material->setSpecular( mSpecular );
-      material->setAmbient( mAmbient );
-      material->setShininess( mShininess );
-      material->setTextureScale( mTextureScale );
-
-      if ( context.isSelected() )
-      {
-        // update the material with selection colors
-        // TODO : dampen the color of diffuse texture
-        //      mat->setDiffuse( context.map().selectionColor() );
-        material->setAmbient( context.selectionColor().darker() );
-      }
+      effect->addParameter( new Qt3DRender::QParameter( QStringLiteral( "diffuseTexture" ), QVariant::fromValue( texture ) ) );
+      effect->addParameter( new Qt3DRender::QParameter( QStringLiteral( "texCoordScale" ), mTextureScale ) );
 
+      effect->addTechnique( technique );
+      material->setEffect( effect );
       return material;
     }
 

src/3d/materials/qgsphongtexturedmaterialsettings.h

@@ -89,6 +89,12 @@ class _3D_EXPORT QgsPhongTexturedMaterialSettings : public QgsAbstractMaterialSe
      */
     float textureRotation() const;
 
+    /**
+     * Returns the opacity of the surface
+     * \since QGIS 3.28
+     */
+    float opacity() const { return mOpacity; }
+
     //! Sets ambient color component
     void setAmbient( const QColor &ambient ) { mAmbient = ambient; }
 
@@ -113,6 +119,12 @@ class _3D_EXPORT QgsPhongTexturedMaterialSettings : public QgsAbstractMaterialSe
     //! Sets the texture rotation in degrees
     void setTextureRotation( float rotation ) { mTextureRotation = rotation; }
 
+    /**
+     * Sets opacity of the surface.
+     * \since QGIS 3.28
+     */
+    void setOpacity( float opacity ) { mOpacity = opacity; }
+
     void readXml( const QDomElement &elem, const QgsReadWriteContext &context ) override;
     void writeXml( QDomElement &elem, const QgsReadWriteContext &context ) const override;
 #ifndef SIP_RUN
@@ -126,6 +138,7 @@ class _3D_EXPORT QgsPhongTexturedMaterialSettings : public QgsAbstractMaterialSe
       return mAmbient == other.mAmbient &&
              mSpecular == other.mSpecular &&
              mShininess == other.mShininess &&
+             mOpacity == other.mOpacity &&
              mDiffuseTexturePath == other.mDiffuseTexturePath &&
              mTextureScale == other.mTextureScale &&
              mTextureRotation == other.mTextureRotation;
@@ -135,6 +148,7 @@ class _3D_EXPORT QgsPhongTexturedMaterialSettings : public QgsAbstractMaterialSe
     QColor mAmbient{ QColor::fromRgbF( 0.1f, 0.1f, 0.1f, 1.0f ) };
     QColor mSpecular{ QColor::fromRgbF( 1.0f, 1.0f, 1.0f, 1.0f ) };
     float mShininess = 0.0f;
+    float mOpacity = 1.0f;
     QString mDiffuseTexturePath;
     float mTextureScale{ 1.0f };
     float mTextureRotation{ 0.0f };

src/3d/qgs3dmapscene.cpp

@@ -943,7 +943,7 @@ void Qgs3DMapScene::finalizeNewEntity( Qt3DCore::QEntity *newEntity )
     }
     else
     {
-      // This handles the phong material with data defined properties.
+      // This handles the phong material with data defined properties and the textured case.
       Qt3DRender::QEffect *effect = material->effect();
       if ( effect )
       {

src/3d/shaders.qrc

@@ -1,5 +1,7 @@
 <RCC>
     <qresource prefix="/">
+        <file>shaders/diffuseSpecular.frag</file>
+        <file>shaders/diffuseSpecular.vert</file>
         <file>shaders/instanced.frag</file>
         <file>shaders/instanced.vert</file>
         <file>shaders/light.inc.frag</file>

src/3d/shaders/diffuseSpecular.frag

@@ -0,0 +1,23 @@
+#version 330
+
+in vec3 worldPosition;
+in vec3 worldNormal;
+in vec2 texCoord;
+
+uniform vec3 eyePosition;
+uniform vec4 ka;
+uniform vec4 ks;
+uniform float shininess;
+uniform sampler2D diffuseTexture;
+uniform float opacity;
+
+out vec4 fragColor;
+
+#pragma include phong.inc.frag
+
+void main(void)
+{
+    vec4 diffuseTextureColor = vec4(texture(diffuseTexture, texCoord).rgb, opacity);
+    vec3 worldView = normalize(eyePosition - worldPosition);
+    fragColor = phongFunction(ka, diffuseTextureColor, ks, shininess, worldPosition, worldView, worldNormal);
+}

src/3d/shaders/diffuseSpecular.vert

@@ -0,0 +1,30 @@
+// copied from qt3d/src/extras/shaders/gl3/default.vert
+
+#version 330
+
+in vec3 vertexPosition;
+in vec3 vertexNormal;
+in vec2 vertexTexCoord;
+
+out vec3 worldPosition;
+out vec3 worldNormal;
+out vec2 texCoord;
+
+uniform mat4 modelMatrix;
+uniform mat3 modelNormalMatrix;
+uniform mat4 modelViewProjection;
+
+uniform float texCoordScale;
+
+void main(void)
+{
+    // Pass through scaled texture coordinates
+    texCoord = vertexTexCoord * texCoordScale;
+
+    // Transform position and normal to world space
+    worldPosition = vec3(modelMatrix * vec4(vertexPosition, 1.0));
+    worldNormal = normalize(modelNormalMatrix * vertexNormal);
+
+    // Calculate vertex position in clip coordinates
+    gl_Position = modelViewProjection * vec4(vertexPosition, 1.0);
+}