quite a newbie to Blender, I started to fiddle around with compositor and created a scene, where a material is illuminating light itself. To enhance the light effect, I moved the mesh with the emitting material to a different RenderLayer, added a blur effect and mixed back together (tried mix and alpha overlay).
However, as the blur effect is rendered separately, as soon as I mix, also parts of the scene (assigned the illuminating material) that should be rendered behind other meshes were rendered with the blur and got mixed atop.
How can I mask / restrict the blur effect to only visible parts in combined scene? is the separate RenderLayers the right approach at all?
I added a rendered output to better visualize the problem. The marked lamps are actually at the back and not visible from that angle. However, the blur of the lamp RenderLayer mixed put the “glow” on top. see http://i.stack.imgur.com/yJoue.png
Best Thorsten