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Old 16-11-2005, 12:09 PM   #1
sjurick
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Default Artifacts in DOF - Mental Ray render

Hello all. I'm getting some strange artifacts in a render using IBL, and some DOF on the camera. The artifacts or fuzz as I refer to it only occur when the DOF on the camera is turned on.

Any ideas of what to change?

I'm using FG and 10000 rays, but doesn't seem to make a diff how many I use.
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Old 19-11-2005, 06:50 PM   #2
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I had a similar problem with my render which I posted on


http://forum.simplymaya.com/showthre...threadid=19050


Someone had a good idea, maybe this will help


"Try upping the Final Gather rays to 500-1000 maybe. If that doesn't work , increase it to 2000. But it might be that the actual model is too small, or too large. Since MR uses actual Model size and size characteristics for FG and Photon emission calculations, if your model is longer then 20 units or smaller then 3 or 4, then you should scale it to be between those two values."
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Old 19-11-2005, 07:07 PM   #3
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Im glad my information is helping peeps!
BTW, theres nothing wrong with fuzzy chrome lol!
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Old 20-11-2005, 03:55 PM   #4
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Well, I checked the objects which were a group of balls and the ground object, and it was at 45 units large. I scaled it down to 9.5 units, rendered again from different angle and changed the DOF settings to match my new angles since the size of the model changed significantly.

Now the problem seems to be worse than better. The first image in this thread used 10000 rays for FG, this image uses 50000 rays. I wonder if the amount of rays is actually hurting me here?

I've attached two more pics. One with 50K FG rays and one with 100 FG rays. I don't think it's the FG doing this or maybe I have another setting wrong.
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Old 21-11-2005, 02:20 PM   #5
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No matter what I do I cannot get rid of the fuzz so I'm thinking that there is a problem with using regular Camera DOF with Mental Ray. Should I be using the Mental Ray Physical Lens DOF node instead? Are there known problems with MR and Maya Camera DOF?
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Old 21-11-2005, 03:50 PM   #6
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you shouldn't be using maya's dof. it's crap basically! What you need ot do is render a depth pass separately and use that in photoshop/shake/after effects etc to blur the image. This way you wouldn't have to re-render with your 50k rays (which is an obscene amount of rays btw! ) and you cna tweak it till it looks perfect. I'd do that rather than mess with the render settings.


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Old 21-11-2005, 04:01 PM   #7
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Ya, I actually tried working with the MR DOF lens and it worked great, but took about a 100 times longer b/c I had to also increase AA way up.

I'm not used to rendering in passes (I know I should become familiar with it so why not now?) I looked it up and see that I have several choices but not Depth. How do I render a depth pass?
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