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

jlait at sidefx.com jlait at sidefx.com
Thu Dec 18 11:52:00 EST 2008


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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