pass-based tinting

Tint the mesh by re-rendering on top of the original one with the marker color.
Also consider the alpha value of the marker color for the mesh.

src/rviz/default_plugin/markers/mesh_resource_marker.cpp

@@ -145,6 +145,13 @@ void MeshResourceMarker::onNewMessage(const MarkerConstPtr& old_message, const M
         if (material->getName() != "BaseWhiteNoLighting")
         {
           Ogre::MaterialPtr new_material = material->clone(id + material->getName());
+          // add a new pass to every custom material to perform the color tinting
+          Ogre::Pass* pass = new_material->getTechnique(0)->createPass();
+          pass->setAmbient( 0.0f, 0.0f, 0.0f );
+          pass->setDiffuse( 0.0f, 0.0f, 0.0f, 0.0f );
+          pass->setSceneBlending(Ogre::SBT_TRANSPARENT_ALPHA);
+          pass->setDepthWriteEnabled(false);
+          pass->setLightingEnabled(true);
           materials_.insert(new_material);
         }
       }
@@ -196,24 +203,32 @@ void MeshResourceMarker::onNewMessage(const MarkerConstPtr& old_message, const M
   { 
     bool depth_write = a >= 0.9998;
     Ogre::SceneBlendType blending = depth_write ? Ogre::SBT_REPLACE : Ogre::SBT_TRANSPARENT_ALPHA;
-
-    // if the mesh_use_embedded_materials is true and color is non-zero
-    // then the color will be used to tint the embedded materials
-    if( new_message->mesh_use_embedded_materials && r == 0 && g == 0 && b == 0 && a == 0 )
-    {
-      blending = Ogre::SBT_REPLACE;
-      depth_write = true;
-      r = 1; g = 1; b = 1; a = 1;
-    }
+    bool tinting = new_message->mesh_use_embedded_materials;
 
     for (const Ogre::MaterialPtr& material : materials_)
     {
       Ogre::Technique* technique = material->getTechnique(0);
-      technique->setAmbient( r*0.5, g*0.5, b*0.5 );
-      technique->setDiffuse( r, g, b, a );
-      technique->setSceneBlending( blending );
-      technique->setDepthWriteEnabled( depth_write );
-      technique->setLightingEnabled( true );
+      Ogre::Pass* pass0 = technique->getPass(0);
+      Ogre::Pass* passT = technique->getPass(technique->getNumPasses()-1);
+      if (tinting)
+      {
+        // modify material's original color to use given alpha value
+        Ogre::ColourValue color = pass0->getDiffuse();
+        color.a = a;
+        pass0->setDiffuse(color);
+        // tint by re-rendering with marker color
+        passT->setAmbient( r*0.5f, g*0.5f, b*0.5f );
+        passT->setDiffuse( r, g, b, std::min(a, 0.5f) );
+      }
+      else
+      {
+        pass0->setAmbient( r*0.5f, g*0.5f, b*0.5f );
+        pass0->setDiffuse( r, g, b, a );
+      }
+
+      pass0->setSceneBlending( blending );
+      pass0->setDepthWriteEnabled( depth_write );
+      pass0->setLightingEnabled( true );
     }
   }