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

Phillip P Prahl pprahl20 at student.scad.edu
Thu Feb 2 15:42:02 EST 2006


is there a file or did I miss something?

----- Original Message -----
From: Jeff Wagner <jeff at sidefx.com>
Date: Tuesday, January 31, 2006 5:22 am
Subject: Re: [Sidefx-houdini-list] uv's along a nurbs spline
> Here's a simple hip file example that builds you the arc length of 
> a 
> curve or face.  Points have to be in order.
> 
> It is a simple matter to convert this to just return the edge 
> length 
> between points. It would be more efficient too!
> 
> 
> -jeff
> 
> Phillip P Prahl wrote:
> 
> >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
> >>>>_______________________________________________
> >>>>Sidefx-houdini-list mailing list
> >>>>Sidefx-houdini-list at sidefx.com
> >>>>https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
> >>>>
> >>>>   
> >>>>
> >>>>        
> >>>>
> >>>_______________________________________________
> >>>Sidefx-houdini-list mailing list
> >>>Sidefx-houdini-list at sidefx.com
> >>>https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
> >>> 
> >>>
> >>>      
> >>>
> >>_______________________________________________
> >>Sidefx-houdini-list mailing list
> >>Sidefx-houdini-list at sidefx.com
> >>https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
> >>
> >>    
> >>
> >_______________________________________________
> >Sidefx-houdini-list mailing list
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> >https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
> >  
> >
> 
> 
> -- 
> Jeff Wagner, jeff at sidefx.com, Senior Technology Consultant
> Side Effects Software, www.sidefx.com, Toronto, Ontario, M5V 3E7
> tel: (416) 504-9876, fax: (416) 504-6648
> 
> 
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