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Bad Antialiasing with 32-bit frame buffer and rendering, specles in hightlights etc.
show user profile  Nanne
This have been a problem for me for a long time and I haven't been able to figure it out yet.

When rendering with mental ray's 32bit frame buffer and to OpenEXR floating-point I get really bad antialiasing in hightlights. I know why, because of the difference in pixel brightness allowed with floating-point makes the smoothing algorithm "fail" to smooth out the highlights correctly. My questing is;

how can I work around this? Any tick or cheat is welcomed! :)


Kristoffer Helander
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read 825 times
9/12/2011 5:54:31 PM (last edit: 9/12/2011 5:54:31 PM)
show user profile  Error404
In VRay there is a similar issue if you have a VERY bright pixel next to a relativly darker pixel (like one pixel reflecting the sun, and another reflecting something else).

The solution in VRay is to clamp the image before the anti-alising happens. I usually clamp at a value of 6, (well above 255 white), this brings down the super bright hightlights enough so that they can be properly anti-alised, but still gives generous highlight detail for composting. Maybe there is a similar setting in Mentalray? -

read 810 times
9/12/2011 6:56:24 PM (last edit: 9/12/2011 6:56:24 PM)
show user profile  Dr. Jim
Ah ha!
Damn!.......Unfortunately, I dont have an anwswer for you Nanne....BUT just helped me out alot. That one has given me issues many times! thanks.

read 797 times
9/12/2011 9:20:24 PM (last edit: 9/12/2011 9:20:24 PM)
show user profile  Error404
Jim, it's especially useful if you are using the sun/sky system, or an HDR that has a very hot hotspot(s) in the HDR that aren't clamped. If I remember correctly, it was usually most problimatic with glossy reflections and sometimes in motionblur, but I think I remember it happening on crisp reflections sometimes too. The setting is in the color mapping section. I've never really needed to go lower than 5 or 6. Still gives plenty of highlight latitude for comp :) -

read 787 times
9/12/2011 11:07:21 PM (last edit: 9/12/2011 11:08:10 PM)
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