[Sidefx-houdini-list] calculating du dv in sops

Andy Walker andy.walker at framestore-cfc.com
Wed Nov 21 09:27:39 EST 2007


There's a primduv expression, does that do what you want? e.g:

-primduv("../texture1",$PR,"P",0,$MAPU+ch("du_off"),$MAPV,1,0)

Cheers,

Andy

Rangi Sutton wrote:
> Andrew D Lyons wrote:
>   
>> Hi,
>>
>> Has anyone got a trick for calculating du dv at sop level?
>>
>> We have a surface with good uv's and we want to derive point vectors
>> that orient along u and v.
>>   
>>     
> Hey Andrew,
>
> I've setup a system where we baked out P to maps, then used cops to 
> calculate the surface derivatives. Should also work with uvs. There's a 
> derivative vop that wraps up easily into a cop node.
>
> Someone might have a better idea that doesn't involve baking though... 
> I'd be keen to hear it!
>
> Cheers,
> r.
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