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

Phillip P Prahl pprahl20 at student.scad.edu
Mon Jan 30 16:22:28 EST 2006


Hey,

So I came up with something that seems a bit more accurate but not so
elegant ...
here is the network:

1. curve sop
2. texture sop set to arc length spline
3. point sop that runs arclen() for each of the points using the uvs and
uses the result as the new uv.

This could then be normalized... with the measure sop as Dan described.
Thanks again for the help!
Phillip






----- Original Message -----
From: Dan Seddon <dan.seddon at framestore-cfc.com>
Date: Monday, January 30, 2006 12:58 pm
Subject: Re: [Sidefx-houdini-list] uv's along a nurbs spline
> You can use the Measure Sop to calculate the "Perimeter" then 
> multiply 
> this against the uv's you've just made and that should give the 
> length 
> along the spline. You can use Attribute Promote to get the 
> Perimeter 
> Attribute into the context of a point expression easily.
> 
> Ta
> 
> Dan
> 
> >So is there no way to get it to calculate the
> >actual length? Only the linear values?
> >Thanks again!
> >Phillip
> >
> >PS I figured the maya comment would get people to respond 
> furiously fast.
> >
> >
> >----- Original Message -----
> >From: Dan Seddon <dan.seddon at framestore-cfc.com>
> >Date: Monday, January 30, 2006 12:48 pm
> >Subject: Re: [Sidefx-houdini-list] uv's along a nurbs spline
> >  
> >
> >>Phillip P Prahl wrote:
> >>
> >>    
> >>
> >>>Hey,
> >>>
> >>>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,
> >>>Phillip
> >>>
> >>>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.
> >>
> >>Cheers
> >>
> >>Dan
> >>_______________________________________________
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> >>
> >>    
> >>
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> >
> 
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