From 4fa41bf62d3abb1f706adce761ec22f5c0a7910b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lo=C3=AFc=20Bartoletti?= <loic.bartoletti@oslandia.com>
Date: Mon, 5 Oct 2020 15:42:56 +0200
Subject: [PATCH] Fix Z interpolation on vertex moved/added by the vertex tool.
 fixes #38561

---
 src/app/vertextool/qgsvertextool.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/app/vertextool/qgsvertextool.cpp b/src/app/vertextool/qgsvertextool.cpp
index 695e74243e3..a3b6504a187 100644
--- a/src/app/vertextool/qgsvertextool.cpp
+++ b/src/app/vertextool/qgsvertextool.cpp
@@ -2080,6 +2080,10 @@ void QgsVertexTool::moveVertex( const QgsPointXY &mapPoint, const QgsPointLocato
 
   QgsPoint layerPoint = matchToLayerPoint( dragLayer, mapPoint, mapPointMatch );
 
+  // needed to get Z value
+  if ( mapPointMatch && mapPointMatch->layer() && QgsWkbTypes::hasZ( mapPointMatch->layer()->wkbType() ) && mapPointMatch->hasEdge() )
+    layerPoint = mapPointMatch->interpolatedPoint();
+
   QgsVertexId vid;
   if ( !geom.vertexIdFromVertexNr( dragVertexId, vid ) )
   {