Simple hard edged volume spotlight with mental ray

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  09 September 2012
Simple hard edged volume spotlight with mental ray

Hi there, I'm a Maya newbie and have a problem I can't seem to get my head around. I'm building an animation where I need a volume light to pass through a moving object and am using mental ray as the renderer, which gives me everything I need in the scene except for one thing. What I am looking for is a way to have a volumetric spotlight with hard edges and no transparency, but that behaves like a light (a bad example would be something like this:

I found tutorials and forum posts on the parti_volume shader which creates light fog and I've managed to do that just fine but the render time shoots from about 5 secs per frame up to about 35 mins as soon as I use raytrace shadows and the parti_volume node. That would make my project impossible to ever finish. I just need a SIMPLE cone, but one that behaves like a light. It's very graphic, high contrast with no softness in the light whatsoever. This should be simple but I can't find a solution.

I've tried a workaround by using a polygon cone and just having the inside of the cone visible, assigning a white lambert to it and grouping it with an actual light. But that doesn't solve the problem of the cone itself not behaving like a light when passing through an object. An example for such a scene would be a train passing in front of this cone of volumetric light and only letting this light through its windows as it's passing by. Does anyone have any ideas of what other things I could try?

I've thought about trying a second render pass with the Maya Software renderer and the Maya Volume Light but so far have had no luck with that. I'm using Maya 2011 on a Mac Pro.
  09 September 2012
Ah, figured it out. Lightfog works wonders. Even if it gives me problems when passing through objects, I can make it work with a bit of tweaking.
  09 September 2012
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