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Rendering only objects close to camera
We have a glass panels spinning around the Y axis in a large ring. The animation picks up speed over time. We need to render the panels in the foreground separate from the ones in the background without loosing the distorted image of the background panels in the foreground ones so we can composite things in the middle. Were new to c4d so if this is obvious, please excuse, but we need help with a solution.
Thank you!
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4 Replies
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Group the front panels under a null and add a compositing tag to the null. In the tag’s properties you’ll see an object buffer tab. Enable an object buffer and note the number assigned.
Then, in render>multipass settings, add an object buffer pass and set the same number as you noted above. Set a save location for the multipass file(s).
What this does is create an alpha for the front panels only. You can use that as a luma matte in your compositor of choice to place the front panels in front of something else.
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Thank you for the info!
Here’s the only wrinkle I see. All the glass panels are the “front” panels at one point or another since they are spinning around the Y axis. The camera is looking down the z axis. The panels orbit the y axis coming close to the camera then arcing around and back away from camera, then across the back of the frame becoming background panels, then back around to the front.
Can I change the camera’s far clipping plane to render one pass with only the front showing and then change the near clipping plane to render only the back?
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Ah, tricky! Unfortunately Cinema supports near clipping but not far clipping, so that’s not going to help. I can think to two solutions:
1) Two-render solution: place a large plane with a “look at camera” tag and a flat black (no specular) material on it so that it blocks the rear objects and render with the object buffer; or
2) One-render solution: give each individual object a compositing tag set to use the same buffer. Then create an Xpresso expression that disables the object buffer based upon distance to the camera.
Which you choose would probably depend on how long the animation takes to render, i.e., if it’s relatively quick, pick No. 1; if it’s a mult-hour affair, go with No. 2.
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Thanks, we’ll give that a try.
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