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# 1 19-04-2011 , 06:07 PM
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Rendering Volumetric Clouds/Ray Marching/ Volume Sattering

Hello, I have a scene in a temple and I really need to have some raylights which make the dust particles visible. I've done a pretty big research, but most of the info i got was for old maya versions (before v.7).

What i do is to make a volume container for the lightrays, assign a transmat in the mental ray shader-override for material and shadow, then add a Parti_volume node for the scattering. So far, so good, after some tweeking and adding a physical light node into a maya lght I get a pretty decent image like the attachment (ignore the wierd shadows). The PROBLEM is, that if i want to get smooth results, i need a pretty BIG container... and i CAN NOT enter with the renderable camera into the volume container. It just doesnt render the light... I have tried adding another light with photon emission into the container, than adding a photon_parti_node into his photon-volume attribute... but still doesnt work. I will be very glad, if there is some experienced mental ray artist (or just anyone who knows what I am talking about user added image ), who can help me solve this problem,. Thank you!

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# 2 20-04-2011 , 02:21 AM
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I don't get the problem. Apart from the mix/max step lens attribute on the partiVolume, volume container size and grain are unrelated as far as I know plus I don't see any noise in the render. I don't use the "physical light", a regular Maya light with a quadratic falloff is more accurate so I don't know if that is part of the problem, it could be dying before it gets a chance to illuminate the scene. I can't imagine why the camera being inside the volume makes the lights not render :s.

This is a render that is using a renderable camera and it's inside the volume primitive.

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# 3 20-04-2011 , 01:03 PM
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This is really nice render! Do you use anything except parti_volume? Again, I tried just a really simple setup - cube container (material transmat, parti_volume), 1 maya point light with quadratic decay (and decent intensity of 50). I havent tweeked the party volume node, but the problem still persists: When the camera is outside the container - theres light, when i cross the bounding box - no light at all!

What could go so wrong? Thank you for the troubleshooting, maybe if you can upload your scene It can be helpful too.

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Last edited by xukca; 20-04-2011 at 01:06 PM.
# 4 21-04-2011 , 03:47 AM
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Actually I was just about to ask you to upload yours as it would make it easier to pinpoint what got messed up.


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# 5 21-04-2011 , 04:08 PM
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Oh well...I just realized, that maybe i havent had anything as background, to actually see the rays... Because these rays does get rendered on top of something else, they dont have its own alpha. After I did a closed interior shot, there are no more problems seeing the scattering, when the camera is inside the container. (actually if i get closed interior my camera SHOULD be inside to render it, lol...) Thank you for the assistance, helped me to clear this up user added image

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