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

kuba roth kuba.roth at gmail.com
Wed May 5 09:05:25 EDT 2010


I had in the past problems importing NURBS surfaces from rhino / 3dsmax -
trim surfaces were not preserved. I would rather export models from
rhino exclusively - it is more accurate then 3dsmax and gives you some
choices how the model is exported. As of a IGES type (in export options)
have a go with 144 - these settings worked best in houdini.

On Wed, Apr 28, 2010 at 6:26 PM, Antoine Durr <antoine at rhythm.com> wrote:

> 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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