[Sidefx-houdini-list] dPds, dPdt troubleshooting...

Simon Barrick simon at primalpictures.com
Thu Aug 31 06:12:57 EDT 2006


There's a very long thread on odForce where Mario did battle with this
problem, it even defeated him... Don't have time to find it at the mo.
But a quick search should turn it up.


-----Original Message-----
From: sidefx-houdini-list-bounces at sidefx.com
[mailto:sidefx-houdini-list-bounces at sidefx.com] On Behalf Of Chris
Lawrence
Sent: 31 August 2006 11:12
To: sidefx-houdini-list at sidefx.com
Subject: Re: [Sidefx-houdini-list] dPds, dPdt troubleshooting...


hello all.

I have no idea how similar mantra and PRMan are internally, but there's 
a way of getting around such problems with polys PRMan.  It's described 
in detail on pixar's forum.  If you're a PRMan customer you should be 
able to find it by searching for 'vertex winding order' on their support

forum at https://renderman.pixar.com.  I'd re-post it here but I'm not 
100% sure I'm allowed to.

Cheers

Chris

Simon Barrick wrote:
> If you are using Polys forget it, you have to hack it. If it's a 
> parametric surface you should be ok.
>
>
> -----Original Message-----
> From: sidefx-houdini-list-bounces at sidefx.com
> [mailto:sidefx-houdini-list-bounces at sidefx.com] On Behalf Of 
> hoknamahn at cgtalk.ru
> Sent: 31 August 2006 10:54
> To: sidefx-houdini-list at sidefx.com
> Subject: [Sidefx-houdini-list] dPds, dPdt troubleshooting...
>
>
> Hey guys!
> Can you explain me how mantra calculates derivatives? I know they 
> depend
>
> on topology of geometry. Does they depend on vertex order? I'm playing
> with anisotropic shader based on dPds, dPdt and do some test. Each
test 
> gives me an unpredictable result.
> Don't let me die from this headache, please!
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