RE: [Algorithms] VIPM and UV texturing

[Tom F. <to...@mu...>]

This is also solved if you start with a low-poly mesh from the artists,
tesselate and displace up to a high-poly mesh, then VIPM down again, but
preserving the original edges. Because the tesselation only uses linear
interpolation for non-geometry attributes, you don't have to deal with nasty
cases like this. Fortunately, coz they are a real pain.

http://www.muckyfoot.com/downloads/tom.shtml

Tom Forsyth - Muckyfoot bloke.
Whizzing and pasting and pooting through the day.

> -----Original Message-----
> From: Jeff Lander [mailto:je...@di...]
> Sent: 09 August 2000 18:06
> To: gda...@li...
> Subject: Re: [Algorithms] VIPM and UV texturing
> 
> 
> Hi all.  New to this discussion but I have recently had a 
> couple of projects where this issue has been very important.
> 
> The issue you bring up about texture coordinates and any sort 
> of mesh LOD system is critical.  That is why I insist that 
> the LOD tools allow artists to hand designate edges that will 
> not collapse.  Any algorithmic method you try and find will 
> fail in certain cases.  The algorithms handle texture 
> projections like sphere and cylinder wraps pretty well but 
> arbitrary UV texturing is a real problem.
> 
> One particular problem I will share that comes up often is 
> when texturing characters.  My system automatically will 
> preserve vertices that have texture coordinate 
> discontinuities.  However, artists will often model a 
> character with only half of the texture (particularly in the 
> face) then just reflect the texture coords to save texture space.
> 
> Now the problem as you would guess is you have the face with 
> coordinates like (1,0) -----  (0,0) ---- (1,0).  Obviously 
> more granular then that. There are no texture coordinate 
> discontinuities so the algorithm says it is ok.  The surface 
> of the face is roughly flat so the internal vertex and edges 
> are good candidates for collapse.  However, you then get the 
> nice situation of  (1,0) ------ (1,0).  Doesn't look so hot.  
> I have the artists tag reflected seam vertices as 
> uncollapsable until very late in the order.
> 
> Let me paraphrase you by saying the algorithms are most 
> efficient when working on trivially textured objects.  
> Anything else requires good artist tools and some TLC.
> 
> -Jeff