View Full Version : Fluid Compositing...

09 September 2009, 12:30 AM
Alloo All,

Does anyone have any tips when it comes time for composting fluids. I have a tornado with a few passes of fluids rendered separately and a background. The issue I am having is when I pull them all into after effects to layer them..I get a white...sometimes black rim around each fluid pass. Ideas?

I think there's an issue with the renders being pre-multiplied. I am not sure tho. Can some explain how pre-multiplication works in maya? Should I render with premult turned "off" or "on" in general ? and why?

Also my other framebuffer settings are set to defaults other than the data type which is set to RGBA 4x32bit.

Thanks in Advace !

Cheers :beer:

09 September 2009, 06:06 PM
your comp application should offer the possibility to unpremultiply your footage, so you could easely check if that is causing the problem.

09 September 2009, 10:03 PM
Thanks.. I'm using nuke. and I tried the premult and unpremult but still i have a weird outline.

09 September 2009, 08:14 AM
Have you checked pre-multiplied when importing to aftereffects?

09 September 2009, 10:18 AM
You should always render your fluid against a black background. Turn off any color or image plane before you render your fluid out. Otherwise you will get your fluid premultiplied against a color other then black and that may be a pain to comp sometimes.

I've also tried to render it unpremultiplied (mental ray gives you that option) but that wasn't good either.

In nuke, there's a difference between using the "premultiplied" ticker on the read node and using a "premult" node. I don't really know that the difference is, but they look different. Most of the times using the "premult" node looks better. Try them borh... maybe both on the same time.

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09 September 2009, 10:18 AM
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