dear vray team i have weird splotches on my geometry…
i have checked the following settings
-double side geometry
-double side material option
-reflect on backside material option
-overlapping geometry
but nothing helps… what do you think is the problem…
many thanks for your help and with best regards
/.mario’
Definately looks like coplanar faces. Raise the secondary Ray Bias (Global Switches Rollout in the Rendersettings) to something like 0.001 or 0.002
Thorsten
or delete them.. 
If you do have double faces, try increasing the secondary rays bias in the Global switches rollout to a small number like 0.001 and see if it helps. If you don’t have any double faces, you can try to rotate the model slightly in one direction. If this still doesn’t help, please email me to vlado@chaosgroup.com
Best regards,
Vlado
I think this is NURBS geometry. Try to rebuild those areas, where you have that looong (or wide) polygons. Manually.
i have changed the secondary ray to the value 0.001 and 0.002
but nothing helps… vlado i prepare the scene for you…
ps. yeah it is a nurbs model from solidworks
/.mario’
*cringe* I get buggard faces like that all the time as all the models I use here are imported from solid works in to max with Poly Trans and its not only vray but MR and Scanline also. Its barely acceptable normally but when doing cutaways like you are there then lately Ive been just rebuilding the part in max that’s giving me the troubles…
-dave
vlado i have sent you the scene…
/.mario’
vlado, i have rendered the scene with the new version you have sent to me… it looks perfekt… 
many thanks…
/.mario’
Can you explain what the issue was please? I have the same problem but there are no issues with the geo. No co-planar faces, I tried adjusting the secondary ray bias etc but nothing works. First time I’ve had this issue
Just fyi, this post was from 2007
Anyway, it could be something anomalous that can or can’t be fixed. As a for instance, if you have a mesh with turbosmooth, set to isoline display, then if you convert it to polys it will
destroy the geometry, with no available fix that I know of. No idea what it manages to do with it but it’s odd. (cue someone with a fix, no doubt 
)
Hopefully your thing won’t be that, but I reckon posting a bit of the mesh be useful to have a look at
Hey. Thanks for the quick response. Sorry to waste your time…it looked very much like a co-planar issue but was actually UVW mapping issues.
Aha! Well that’s an easy fix then
Also I never consider my time wasted, unless it’s like a client meeting for no discernable reason that I have to travel to tomorrow…*sigh
Bart, can you please explain this turbosmooth issue more thoroughly, trying to understand it fully. Does turning off isoline display help? When I have issues with turbosmooth I usually try OpenSubdiv or MeshSmooth as well. I tend to prefer OpenSubdiv overall.
All it is, and is simple to test, is that when the turbosmooth is set to display as isolines, then the conversion totally messes up the mesh.
I guess there must be an underlying reason why it occurs, but it’s very odd and could easily catch someone out who isn’t aware.
For instance, if you have a bunch of models you got from a 3rd party which have that option enabled on some parts - you
start attaching things and may not notice until it’s done and botched, then wonder wtf is going on
Anyway it’s simple enough to avoid or undo if you accidentally do it, by unchecking that option.
The only reason I ever use it is to clear up the display of a dense mesh when doing hard surface stuff, which is how I first noticed it occurring as I iterated to a final mesh.
EDIT: Sorry, I should have been more explicit in what it specifically does; so e.g. one poly is turbosmoothed into 4 polys, which, when converted to editable, shows one poly ‘smoothed’ though which has an extra vertex in each edge, thus destroying the mesh. So it only converts it halfway I guess.
