[Sidefx-houdini-list] my non-rational NURBS surface gets rational when written to disk

Robert Kelly isstuff at gmail.com
Thu Dec 18 12:08:30 EST 2008


Thank you, that did the trick!

As a side note I tried to set the weights on all points to 1 after it was
made rational, that didn't work. For future reference, is there a way to
convince a nurbs curve / surface to go back to non-rational?

2008/12/18 <jlait at sidefx.com>

> On Wed, Dec 17, 2008 at 01:47:47PM -0500, Robert Kelly wrote:
> > my non-rational NURBS surface gets rational when written to disk!?
> > And is messing up my creep!
> >
> > i am making a fairly heavy network and wanted to include some writing and
> > reading from disk to make it a bit more stable. Only to find that my
> creep
> > went funny when I read it from disk. after some head scratching i spotted
> > that the one from disk becomes  rational when read in, while the geometry
> > that it is meant to be writing to disk is non-rational.
> >
> > So how do I ether have it read and write properly {BUG?} or as a band aid
> > solution make my now rational nurbs surface back into a non-rational one?
>
>     Bandaid solution:
> Point Sop
>    New Weights
>        delete channel, set to 1.
>    Do this in the Skin SOP before your geometry output to catch the
> culprit at the source.
>
>    What is going wrong is that slight numerical tolerance issues are
> making the weights non-one.  This causes the geometry to be flagged as
> rational when read from disk.  When operated in memory, Houdini only
> checks to see if they are non-one if something happens that should
> make them non-one.  Since the skin shouldn't result in non-one
> weights, we don't check, so the NURBs stays flagged as non-rational.
> --
>        - Jeff Lait
>
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