3d: Use absolute clamping for 3d data by default

When providing a project DTM/DEM, the default behavior for vector
feature with a z-component is to offset the $z coordinates from the
terrain elevation model in the elevation profile view. However, the
geometry coordinates are supposed to be absolute.

So it makes more sense, to only use the $z coordinate by default in
that case.

The different unit tests are updated accordingly.

Closes: #59757

src/3d/symbols/qgsline3dsymbol.h

@@ -123,7 +123,7 @@ class _3D_EXPORT QgsLine3DSymbol : public QgsAbstract3DSymbol SIP_NODEFAULTCTORS
 
   private:
     //! how to handle altitude of vector features
-    Qgis::AltitudeClamping mAltClamping = Qgis::AltitudeClamping::Relative;
+    Qgis::AltitudeClamping mAltClamping = Qgis::AltitudeClamping::Absolute;
     //! how to handle clamping of vertices of individual features
     Qgis::AltitudeBinding mAltBinding = Qgis::AltitudeBinding::Centroid;
 

src/3d/symbols/qgslinevertexdata_p.h

@@ -77,7 +77,7 @@ struct QgsLineVertexData
     bool withAdjacency = false; //!< Whether line strip with adjacency primitive will be used
 
     // extra info to calculate elevation
-    Qgis::AltitudeClamping altClamping = Qgis::AltitudeClamping::Relative;
+    Qgis::AltitudeClamping altClamping = Qgis::AltitudeClamping::Absolute;
     Qgis::AltitudeBinding altBinding = Qgis::AltitudeBinding::Vertex;
     float baseHeight = 0;
     Qgs3DRenderContext renderContext; // used for altitude clamping

src/3d/symbols/qgsmesh3dsymbol.h

@@ -354,7 +354,7 @@ class _3D_EXPORT QgsMesh3DSymbol : public QgsAbstract3DSymbol
 #endif
 
     //! how to handle altitude of vector features
-    Qgis::AltitudeClamping mAltClamping = Qgis::AltitudeClamping::Relative;
+    Qgis::AltitudeClamping mAltClamping = Qgis::AltitudeClamping::Absolute;
     float mHeight = 0.0f;                                           //!< Base height of triangles
     std::unique_ptr<QgsAbstractMaterialSettings> mMaterialSettings; //!< Defines appearance of objects
     bool mAddBackFaces = false;

src/3d/symbols/qgspoint3dsymbol.h

@@ -175,7 +175,7 @@ class _3D_EXPORT QgsPoint3DSymbol : public QgsAbstract3DSymbol SIP_NODEFAULTCTOR
 
   private:
     //! how to handle altitude of vector features
-    Qgis::AltitudeClamping mAltClamping = Qgis::AltitudeClamping::Relative;
+    Qgis::AltitudeClamping mAltClamping = Qgis::AltitudeClamping::Absolute;
 
     std::unique_ptr<QgsAbstractMaterialSettings> mMaterialSettings; //!< Defines appearance of objects
     Qgis::Point3DShape mShape = Qgis::Point3DShape::Cylinder;       //!< What kind of shape to use

src/3d/symbols/qgspolygon3dsymbol.h

@@ -186,7 +186,7 @@ class _3D_EXPORT QgsPolygon3DSymbol : public QgsAbstract3DSymbol SIP_NODEFAULTCT
 
   private:
     //! how to handle altitude of vector features
-    Qgis::AltitudeClamping mAltClamping = Qgis::AltitudeClamping::Relative;
+    Qgis::AltitudeClamping mAltClamping = Qgis::AltitudeClamping::Absolute;
     //! how to handle clamping of vertices of individual features
     Qgis::AltitudeBinding mAltBinding = Qgis::AltitudeBinding::Centroid;
 

tests/src/3d/testqgs3drendering.cpp

@@ -2003,6 +2003,15 @@ void TestQgs3DRendering::testAmbientOcclusion()
   mapSettings.setLightSources( { defaultPointLight.clone() } );
   mapSettings.setOutputDpi( 92 );
 
+  QgsPhongMaterialSettings materialSettings;
+  materialSettings.setAmbient( Qt::lightGray );
+  QgsPolygon3DSymbol *symbol3d = new QgsPolygon3DSymbol;
+  symbol3d->setMaterialSettings( materialSettings.clone() );
+  symbol3d->setExtrusionHeight( 10.f );
+  symbol3d->setAltitudeClamping( Qgis::AltitudeClamping::Relative );
+  QgsVectorLayer3DRenderer *renderer3d = new QgsVectorLayer3DRenderer( symbol3d );
+  mLayerBuildings->setRenderer3D( renderer3d );
+
   // =========== creating Qgs3DMapScene
   QPoint winSize = QPoint( 640, 480 ); // default window size
 

tests/src/python/test_qgsmesh3dsymbol.py

@@ -38,9 +38,9 @@ def test_getters_and_setters(self):
         self.assertEqual(symbol.cullingMode(), Qgs3DTypes.Front)
 
         # Test altitude clamping
-        self.assertEqual(symbol.altitudeClamping(), Qgis.AltitudeClamping.Relative)
-        symbol.setAltitudeClamping(Qgis.AltitudeClamping.Absolute)
         self.assertEqual(symbol.altitudeClamping(), Qgis.AltitudeClamping.Absolute)
+        symbol.setAltitudeClamping(Qgis.AltitudeClamping.Relative)
+        self.assertEqual(symbol.altitudeClamping(), Qgis.AltitudeClamping.Relative)
 
         # Test height
         self.assertEqual(symbol.height(), 0.0)
@@ -152,9 +152,9 @@ def test_equality(self):
         self.assertEqual(symbol1, symbol2)
 
         # Test altitude clamping
-        symbol2.setAltitudeClamping(Qgis.AltitudeClamping.Absolute)
-        self.assertNotEqual(symbol1, symbol2)
         symbol2.setAltitudeClamping(Qgis.AltitudeClamping.Relative)
+        self.assertNotEqual(symbol1, symbol2)
+        symbol2.setAltitudeClamping(Qgis.AltitudeClamping.Absolute)
         self.assertEqual(symbol1, symbol2)
 
         # Test height