Group all the Objects you want as different layers and parent them to Null objects — as long as it doesn’t interfere with the scene. I do this so I can label the null ” wheel layer ” and so on. Then add compositing tags to each layer and set the object buffer — in your situation you’ll need to make 4 separate object buffers for each layer.
Go into your render settings and set multipass — then make sure it sends out an ‘object buffer’ multipass layer. This isn’t going to be JUST the wheels — it is going to be an alpha channel of JUST the wheels that you’ll stencil over the entire quicktime. Make sure you export out an AE file.
You’ll need to pre-comp all the multipass layers on the main quicktime. It takes a little longer to render each frame with the mattes, but it looks cool. The ae file will bring in a camera. I noticed that anything longer than 15seconds bogs down a dual 2.7 w/4gigs of ram (they bought me that…nice compy). When you import your c4d file into ae have patience. If you get the whirlie or hourglass go watch tv for a few minutes — it’ll eventually import.
Check out your manual too…it explains the object buffer bit….
Nicholas Toth
Freelance Animator
nicholastoth.com