Fix facesColoredPerFaceFlatShaded rendering.

ObjectTypes/VolumeMeshObject/VolumeMeshNodeT.cc

@@ -860,6 +860,12 @@ void VolumeMeshNodeT<VolumeMeshT>::getFaceRenderObjects(IRenderer* _renderer, GL
         ro.shaderDesc.numLights = -1;
         ro.shaderDesc.shadeMode = SG_SHADE_GOURAUD;
     }
+    else if (_drawMode & drawModes_.facesColoredPerFaceFlatShaded)
+    {
+        ro.shaderDesc.vertexColors = true;
+        ro.shaderDesc.numLights = -1;
+        ro.shaderDesc.shadeMode = SG_SHADE_FLAT;
+    }
     else
     {
         ro.shaderDesc.numLights = 0;