Merge 389e8f82179eac822c7295a9f1d7dd74928583a1 into d63653925c5c55cf16618e5ed16fb71f0c9620dc

Add transparency layer to QgsPoint3DBillboardMaterial entities,
so that they get rendered in the transparent pipeline instead
of the opaque pipeline. Adjust alpha discard threshold in billboard
fragment shader to permit semi-opaque pixel rendering.

Pros: nicely smoothed billboard symbol rendering, without harsh
aliased edges. Billboard symbols can use semi-transparent colors.

Cons: Introduces ordering issues for billboards, where billboards
which should be shown behind others will appear in front from
some angles (i.e. the same issue as we get for 3d polygon objects
with transparency)

src/3d/qgs3dmapscene.cpp

@@ -878,6 +878,14 @@ void Qgs3DMapScene::finalizeNewEntity( Qt3DCore::QEntity *newEntity )
         }
       }
     }
+    else if ( QgsPoint3DBillboardMaterial *billboardMaterial = qobject_cast<QgsPoint3DBillboardMaterial *>( material ) )
+    {
+      Qt3DCore::QEntity *entity = qobject_cast<Qt3DCore::QEntity *>( billboardMaterial->parent() );
+      if ( entity && !entity->components().contains( transparentLayer ) )
+      {
+        entity->addComponent( transparentLayer );
+      }
+    }
     else
     {
       // This handles the phong material with data defined properties, the textured case and point (instanced) symbols.

src/3d/shaders/billboards.frag

@@ -7,9 +7,8 @@ out vec4 fragColor;
 
 void main(void)
 {
-
   fragColor = texture(tex0, vec2(UV.x, 1.0f - UV.y));
 
-  if (fragColor.a < 0.5)
+  if (fragColor.a < 0.01)
       discard;
 }