I am doing a simple scene in Cycles with glass shards. I added a plane with the image I want as a background. However, I need to render only the glass shards, and their distortion of the background, and not the background it self. How could this be done?
I figured it out myself :P
I needed to put the shards on layer 1, and background on layer 2. Then I shift-click both layers, so they are both visible. Then, I opened up render-layers and set the scene to layer 1 and layer 2 if they were not showing, and I selected only layer 1 under the "Layer" tab.