View Full Version : multi-pass material pass?

11 November 2005, 07:52 AM
Hi. I'm wondering if there's a way to render a buffer for just one mapped material on an object. for example, i have a render of a car and i want a pass that only buffers the car's paint color. Is this possible?

11 November 2005, 08:02 AM
i'm afraid only if you can manually do it, it's more normal to split the painted sections off into seperate objects and then use object buffers to create buffer passes for masks in this sort of situation.

11 November 2005, 08:23 AM
I was afraid of that. One solution I'm trying out right now is rendering a material color pass, and since the colors are different enough, pull a matte for the color i want to change and use it as a buffer. Is this multi-pass option i'm trying to do something that other 3d platforms have?

11 November 2005, 08:30 AM
with renderman you can set up a sort of "user data" style pass, where you can tell it what to do and would have no problem with this. in xsi you have a multipass system which creates instances of your scene which you can then modify and each will be rendered seperately, which when it comes down to it is basically the same as doing it manually, the benefit is that any changes you make to the original partition/scene are passed down to the instances, but effectivly apart from that it's like duplicating the scene and changing it's settings, then batch rendering. maya has a new passes system in r7 which is more or less similar to xsi's.

11 November 2005, 02:51 PM
You can create a black matte material (no channels selected) and add it to the stack in the object manager. Then move the desired material to be isolated to the far right with the black matte to the immediate left. Then render out a pass. Repeat for each material you want to separate.

Anyway, that's one of the "manual" methods. :hmm:

11 November 2005, 05:51 PM
not sure I understand your process, acme. doesn't the black matte shader get covered up by the shader to the right of it? What purpose then does it serve? just curious if i'm missing a step here.

11 November 2005, 08:07 PM
I use the black matte (a null texture) to block out any areas not covered by the right-most texture/material. This makes a black background render, no objects visible, with just the desired texture areas visible. A manual mask might be required to composite in Photoshop/AE.

But, hey, it works for me. ;)

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