How to make background animation?

How can I pre-key out the background in blender?

• I am starting making videos and one of the first thing to do is make backgrounds, props and animals or other beings. On my way to this I have found the problem that 3D rendering programs can be expensive, but luckily Blender is around. I have had no problems with blender other than the background. I need to key out the background but is hard as I have so many colors in my animation, is there anyway I could key it out in Blender. I keep hearing about alpha channels. Thanks ~Joe

• Answer:

  Alpha channel is much better option then keying out a color. Goto Render tab in blender, search for the output panel select a format which supports alpha channel(png, tiff) and enable RGBA. Now with these settings you can use the output images as sequence in any video compositing software without having to key out any color cause it will leave the background with zero alpha. If you want to use the render in Blender video editor itself then: 1) Add your background image or movie in video sequencer. 2)Add scene to video sequencer, above your background image or movie. 3)Select scene in the video sequencer goto edit strip panel(left side in video sequencer, press n if not present) select Alpha over in Blend pull down menu. 4)Render.