[Sidefx-houdini-list] uv's along a nurbs spline

Dan Seddon dan.seddon at framestore-cfc.com
Mon Jan 30 15:48:22 EST 2006

Phillip P Prahl wrote:

>I'm trying to map a U value along a NURBS spline.
>Imagine a spline that has 4 points:
>1. 0,0,0
>2. 0,0.25,0
>3. 0,0.60,0
>4. 0,1.00,0
>Now all I need is the uv's to reflect the distance
>between these points so that the u value would be:
>1. 0.00
>2. 0.25
>3. 0.60
>4. 1.00
>This could obviously be done by merely mapping $TY to $MAPU.
>However, now imagine a nurbs curve that twists and turns -
>I need the u value to reflect the length along the curve
>to any given point (the arc-length or chord-length).
>Hope someone has an answer ...
>Thanks for your time,
>PS Maya does this automatically :)

Yup - but unlike Maya, Houdini gives you a choice ;)

Get a UV Texture Sop and set it to Texture Type: Arc Length Spline
and Apply To: Point Texture
If you want your UVs to be between 0 and 1 then first you'll need to do:
Basis Sop->Map:

       Origin = 0
       Length = 1

You'll only get the exact result you ask for above if your nurbs is 
linear however.



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