Rendering issue. Any suggestions?

#1

I’ve been working with Renderman 21 for a while now and so far all is working out well. I rendered out a ring today and I noticed some issues along the edge of the ring. I can’t figure out what is causing this distortion. My geometry count is high as well as the rendering settings but this one part of rings edge continues to render out distorted.
Any idea what may be the cause?

Thank you.

#2

This looks like a white clamping issue instead of a geometry issue.

Many render engines that render 32 bit colorspace (keeping exposure data intact for EXR/HDR image formats) will try to display this above 1.0 white the best it can on a computer monitor but ultimately looks aliased. In vray/redshft/arnold etc you can clamp the white value to make it easier for the very bright areas to anti-aliased easier. Renderman has this clamp value somwhere but I haven’t used it since RIS20 was released since that was the last reyes engine release.

If you clamp the white to 4.0 or less… even 1.0 clamping will likely soften this brightness stepping you are seeing.

Unless this isn’t the issue. but it looks like unclamped white values. You can check it if you have nuke by opening the exr output in nuke and floating the mouse over the area and seeing what the rgb values report back.

#3

There are two ways to deal with this apparent aliasing of bright edges.

  1. Do the filtering and tone mapping in your compositor to deal with the bright areas when using floating point files (like exr)
  2. Use the feature that’s built in to RenderMan. https://renderman.pixar.com/resources/RenderMan_20/risFiltering.html

look for the remap fields in the render settings dialog>passes tab

Pete

#4

Hi all.

Thanks for your suggestions.
I was working on the lighting for this project for a couple of days so my eyes were starting to get very tired. After taking a break I came back and realized that the edge of the model (finger ring) didn’t have sufficient geometry. I subdivided the outside edge to smooth it a little more and it fixed the problem right away. Go figure, huh?

Thanks again for your input.