[Sidefx-houdini-list] Rendering NURBs... again...

Antoine Durr antoine at rhythm.com
Wed Apr 28 12:26:47 EDT 2010


Have you verified that the patch bases are the same in Houdini as they 
were in Rhino?  If the basis order got inadvertently changed, e.g. from 
4 to 3, or even just on the trim curve itself, that might explain the 
separation artifacts you're seeing.

-- Antoine

Abdelkareem Abonamous wrote:
> I'm sure that this topic has come up before (heck, I might have  
> contributed to that at some point, just can't recall any of it).
> 
> Trying to render NURBs straight as NURBS (as opposed to pre- 
> tessellating). And I keep running into artifacts, specially around  
> trim edges (tiny gaps between the trimmed surfaces). The models come  
> in as IGES out of rhino, and both rhino and 3dsmax render them without  
> artifacts at all, but despite my hardest effort (using all sorts of  
> weird coving/no-coving/dicing methodology voodoo), I can't make the  
> gaps disappear. Converting to polys is prohibitive due to very heavy  
> models and big closeups. I thought that IGES might be the issue  
> (accuracy), so I scaled up the original in rhino by about 100,  
> exported it then, and the same problem shows up. And besides, 3dsmax  
> dealt with the same IGES file just fine.
> 
> It's immensely frustrating and It's driving me insane :D FYI I'm  
> rendering in micropoly mode and there is no raytracing involved so far  
> (so it can't be a raytracing bias issue). Any tips out there?
> 
> cheers,
> Abdelkareem
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