Re: [Algorithms] Representing Animation Key Frame with Quaternion + Translation Vector

[Cedric P. <mor...@pl...>]

Hi,
Interesting topic, i am currently doing skinning and i would like to 
have some other point of views. I use similar technique from 
http://www.intel.com/cd/ids/developer/asmo-na/eng/172124.htm
1 - in the pre process i identify set of vertex by uniq transform set 
(eg v0 v1 and v2 are transformed by bone1 and bone2 with the weight1 and 
weight2).

2 - Then i have a flaten list of transform by vertex group to update 
each frame eg:
so to have the final transform (in animation space) for the set of 
vertex ( v0, v1,v2) i have to collapse ( transform bone1 * w1 + 
transform bone2 *w2)

3 - Then in cpu or gpu i have to do only one matrix * the vertex. 
Because previous work computed the concatenation of matrix, it reduces 
the number of matrix needed in the vertex shader.

the method is describe here,
http://www.intel.com/cd/ids/developer/asmo-na/eng/172124.htm
What do you think about that ?

Cedric

Jon Watte wrote:
> Lim Sin Chian wrote:
>   
>> Just wondering if anyone has done this before and whether it is really 
>> better in terms of performance and accuracy.
>>     
>
> I'm under the impression that everybody does that. Not only does it save 
> space (assuming you don't need scale), but it also interpolates much 
> better. Interpolating between two frames with a matrix looks pretty 
> crufty. The only thing to watch out for is to make sure you go the 
> "short way" around -- dot product the two quaternions, and if the 
> outcome is negative, negate all the values of the destination.
>
> To compose quaternions, you just multiply them. Because it's a 
> rotation-translation pair, if it's parent relative, then you apply the 
> parent rotation to the child translation, and then apply your own 
> rotation around that point.
>
> Sincerely,
>
> jw
>
>
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-- 
+33 (0) 6 63 20 03 56  Cedric Pinson mailto:mor...@pl... http://www.plopbyte.net