[FEATURE] Add rule-based 3D renderer

Next to the "simple" vector layer 3D renderer that uses a single symbol
for all features, this new renderer allows definition of hierarchy
of rules with 3D symbols to define how a layer is rendered in 3D view,
similar to how 2D rule-based rendering or labeling works.

This commit does not add any GUI support yet.

src/3d/CMakeLists.txt

@@ -15,6 +15,7 @@ SET(QGIS_3D_SRCS
   qgsphongmaterialsettings.cpp
   qgspointlightsettings.cpp
   qgsraycastingutils_p.cpp
+  qgsrulebased3drenderer.cpp
   qgstessellatedpolygongeometry.cpp
   qgstilingscheme.cpp
   qgsvectorlayer3drenderer.cpp
@@ -101,6 +102,7 @@ SET(QGIS_3D_HDRS
   qgsphongmaterialsettings.h
   qgspointlightsettings.h
   qgsraycastingutils_p.h
+  qgsrulebased3drenderer.h
   qgstessellatedpolygongeometry.h
   qgstilingscheme.h
   qgsvectorlayer3drenderer.h

src/3d/qgs3dmapscene.cpp

@@ -43,6 +43,7 @@
 #include "qgschunknode_p.h"
 #include "qgsmeshlayer.h"
 #include "qgsmeshlayer3drenderer.h"
+#include "qgsrulebased3drenderer.h"
 #include "qgsterrainentity_p.h"
 #include "qgsterraingenerator.h"
 #include "qgstessellatedpolygongeometry.h"
@@ -539,6 +540,10 @@ void Qgs3DMapScene::addLayerEntity( QgsMapLayer *layer )
     {
       static_cast<QgsVectorLayer3DRenderer *>( renderer )->setLayer( static_cast<QgsVectorLayer *>( layer ) );
     }
+    else if ( layer->type() == QgsMapLayer::VectorLayer && renderer->type() == QLatin1String( "rulebased" ) )
+    {
+      static_cast<QgsRuleBased3DRenderer *>( renderer )->setLayer( static_cast<QgsVectorLayer *>( layer ) );
+    }
     else if ( layer->type() == QgsMapLayer::MeshLayer && renderer->type() == QLatin1String( "mesh" ) )
     {
       static_cast<QgsMeshLayer3DRenderer *>( renderer )->setLayer( static_cast<QgsMeshLayer *>( layer ) );