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Arcon
11-05-2005, 09:23 AM
in Maya 6.5 there's an option in the object's shape node to override FG, including disabling casting/receiving FG. when i've tried using this it produces dark anomolies on other surfaces (see test image below).

the first image is FG on everything. in the second image the oval has FG-cast and receive disabled with the overrides. the pink oval is actually a flat plane with mapped transparency, so i'm not sure if the problem is transparency related but its definitely FG specific (FG disabled in globals fixes the problem). is it something to do with rays or trace depth...? i tried raising values of various things but it didn't help.

any ideas welcome, its pretty late so i have none ;)

http://www.cipher.co.nz/wip/fg_artifact.jpg

akewt
11-05-2005, 10:31 AM
its actually in the top render too but because you have the FG casting bright pink on the floor its less obviuos. it looks like your alphered plane is casting some occlussion on the floor.

hope this makes it clearer.

kev

Arcon
11-05-2005, 08:04 PM
hi - thanks for your reply :)

yeah now that you mention it its still happening in the top one too...hmmm. would you know why the alpha plane is doing that though, and how i would stop it lol...

another weird thing is with the FG override enabled the render took a second longer to render... i would've thought less scene FG = less render time...

PhillipCrond
11-05-2005, 11:58 PM
The fact that it's not casting or receiving FG doesn't mean that it's transparent to FG rays completely. It will still stop an FG ray in its path, it just won't contribute to the lighting of the object. Making an object transparent to FG, yet opaque to the camera is going to require that you do a couple of render passes, one of your final gather solution without the object, and one of your color/reflection pass with the object in place.

Unless there's some MR shader trickery to get around this, you're forced to composite. I've run into this as well, and comping was quick and painless.

Arcon
11-06-2005, 12:48 AM
Unless there's some MR shader trickery to get around this, you're forced to composite. I've run into this as well, and comping was quick and painless.

well that depends on how many objects are in the scenes, and how many are reflective etc ;) i will have to render out in passes though for animated objects, thankfully there are only a few dozen.

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