Re: [Algorithms] calculating weights for blending arbitrary number of animations

[Yordan G. <yo...@gy...>]

Thanks for the paper. It references another paper: Articulated Body
Deformation from Range Scan Data
http://grail.cs.washington.edu/projects/digital-human/pub/allen02articulated.html


Anyway they both apply the following formula:

Wi = 1/(D(p,pi) - 1/D(p,pk)

where D is a distance function and p1... pk are the nearest pose parameters
and p is the supplied new parameter. They also implied that Euclidian
distance does the job. But I struggle to understand how this works when
distance is 0 in either part of the binom... simply wont work.
Its clear that I'm missing something.

I also saw a reference to another method called cardinal radial basis
functions and a reference to a paper that I'm not able to find/download on
the web.  SLOAN, P.-P., ROSE, C., AND COHEN, M. F. 2001. Shape by example.
In Proceedings
of 2001 Symposium on Interactive 3D Graphics.

Does anyone have a link?



-Yordan

----- Original Message ----- 
From: "Alex Mohr" <am...@cs...>
To: <gda...@li...>
Sent: Tuesday, November 30, 2004 7:38 PM
Subject: Re: [Algorithms] calculating weights for blending arbitrary number
of animations


> This from SIGGRAPH last year may be relevant.  Check the video, and I
> believe the paper starting at section 4 would be most useful, but
> reading the whole thing is probably worthwhile.
>
> http://www.cs.wisc.edu/graphics/Gallery/Kovar/ParamMotion/
>
> Alex
>
>
> >Hello,
> >
> >Imagine a soldier (or  character with a weapon of some kind). We are
tying
> >to get its weapon (two weapons, two handed weapon) to point into the
> >direction of aiming.
> >
> >We have 9 animations. Each represents a pose into a certain direction.
Each
> >"pose" animation has a vector associated with it.
> >For a given character aiming direction vector we compute weight for each
> >animation to contribute into the final anim.
> >
> >Question is: Given N (in this paricular case 9) vectors and the aiming
one
> >how to compute good weights that max to 1.0 when the aming coincides with
> >them? (Did I mention that weights need to add up to 1.0? but of course
you
> >know that...)
> >
> >We have tried few methods and we have a couple of working but far from
ideal
> >bodged solutions. I'm sure someone has solved this problem elegantly with
> >some clever maths. A lot of games seem to do that kind of thing although
in
> >some cases IK can be applied.
> >
> >One solution that gives smooth results is just a dot product.
> > Wi = Vi dot Va  where Wi are normalized afterwards with Wi = Wi/sum(Wi)
(Wi
> >weight for each bone, Vi - Direction vectors for anims, Va - aim vector)
> >Unfortunately, this only works perfectly if all direction vectors (Vi)
are
> >perpendicular to each other so when they max out no other anim
contributes
> >to the final. It still works in other cases but the results are not
accurate
> >enough for us.
> >
> >We have also explored few solutions where assumptions have been made that
> >some vectors lie in a certain plane but I'm looking for a generic
solution
> >that will work in all cases.
> >
> >Thanks,
> >Yordan
> >
> >
> >
> >
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