ZBrushCentral

Mental Ray Artifacts

ZBrush Usage Questions
#1

Hey Guys,

I can’t quite figure out why I am getting these bizarre artifacts. In Zbrush, there appears to be nothing abnormal on the sculpt but when I render in Mental Ray I get this result. I’de tremendously appreciate any help you anyone can offer.

Stats:
-Rendering in Mental Ray with .map file coverted from .tif. (But have the same problem with the original .tif)
-Levels tweaked in Photoshop
-Exported in ZBrush using Multi Displacement 2 Exporter settings for Maya
-ZBrush sculpt is about 2.2 million polys.
-Applying Sub-D approx editor on clean OBJ mesh with setting to Spatial:
min=3 max=5
-Every other area of mesh, including the body works fine…weird
-When I apply the file to the BMP channel only, it works fine.
-When I render with Maya Software, it appears fine
-Render double sided is off on the shape node
-Feature Displacement is off
-Mesh has correct facing Normals

Thanks guys, Shannon

Question.jpg

Shannon Thomas [www.ShannonThomas.info](http://www.ShannonThomas.info)

[email protected]

#2

I dont have maya, but it looks like you did a local subdivision of the model. Everywhere this subdivision meets the rest of the mesh it causes problems. I would subdivide the rest of the mesh to match.

#3

Thanks for the quick responce. It makes sense what you said but there are a lot of other areas on the mesh, and all over the rest of the body where there are not problems at all. Strange.

#4

Well, when I changed the mesh back to Polys and smoothed it to level 2 the artifacts disappeared. Strange that I have no problem with other areas when in Sub-D Mode. Any Maya users out there? Thanks.

#5

Maya subd’s have always been problematic. The theory is clever, but the implementation has so many little ‘gotchas’ that people tend to avoid them. The main problems have been

-limited options for uv’s (unless you uv the poly cage before converting)
-slow skinning
-mystery construction nodes that get scattered everywhere
-limited mentalray support

Looks like you’ve been bitten by the 4th point. :slight_smile:

Rather than use maya subds, convert your shape back to poly’s and use the mentalray approximation editor to use native mr subds. Scott Spencer has written a fantastic tutorial for this, should answer all your questions:

http://206.145.80.237/zbrush/media/ZBMAYA-pipeline.zip