RE: [Algorithms] VIPM and UV texturing

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

Hoppe's version of the QEM metric that deals with attributes does help with
these sorts of things, and may well be just what the doctors ordered. It
certainly deals with similar problems with vertex colours, as demonstrated
very convincingly by the "baboon" picture done entirely with untextured
vertex-coloured triangles.

For animation, I have in my brain an idea about having several typical poses
for the character in memory while calculating the QEMs, and using the metric
that gives you the _greatest_ error of all the poses when deciding which
collapse is best to do. That way things like elbows and knees won't vanish
far too early, but the artists don't need any specialist knowledge, or need
to worry about default poses too much.

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

> -----Original Message-----
> From: Jeff Lander [mailto:je...@di...]
> Sent: 10 August 2000 16:09
> To: gda...@li...
> Subject: RE: [Algorithms] VIPM and UV texturing
> 
> 
> I started adding some code to the metric to try and detect 
> and weight the case but never got it to work well with all 
> the other settings in the metric.  Having the artistic 
> control was just more flexible.  We are doing a new rev on 
> the tool and I have someone else working on it so I will have 
> him revisit that.
> 
> There are a lot of aspects to the decimation that I am 
> looking at for the next rev.  Our current metric doesn't take 
> into count the changes brought by animation.  It uses the 
> rest pose which as you know artists can build in strange ways 
> to make weighting easier.  I don't know if anyone else has 
> looked at this.
> 
> Also, the current algorithm leads to a bit of hollowness on 
> the low end of the scale.  It does decent at preserving the 
> base shape but things like the legs get a bit thin.  I am 
> thinking about adding in some volume preservation (like Hoppe 
> had in his recent paper on metrics) or trying some 
> image-space stuff from orthogonal angles to address this.
> 
> -Jeff
> 
> At 05:58 AM 8/10/2000 -0700, you wrote:
> >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.
> >
> >Can you not algorithmically detect this situation as well? 
> Compute the
> >tangent-normal basis for the polygon, and look at the 
> derivative of the
> >texture coordinates w.r.t the tangent vector - if this 
> changes sign you have
> >a seam.
> >
> >More work, I grant you, and I admit not as flexible as 
> having a tool that
> >lets the artists do the markup, but still possible.
> >
> >Tony Cox - DirectX Luminary
> >Windows Gaming Developer Relations Group
> >http://msdn.microsoft.com/directx 
> >
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