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

[Jon W. <jw...@gm...>]

pontus birgersson wrote:
>  
> Intressting topic, how would you go about skinning a mesh using this 
> kind of data? Is hardware skinning still an option? I assume matrix 
> and vector operations are heavily optimized on current gpus.

Yes, you can still hardware skin. In fact, you can do more bones per 
pass, because offset+quaternion is only 2 constant registers, whereas a 
matrix is at least 3 constant registers. The code to transform a vertex 
by a quaternion is slightly more expensive than the code to transform by 
a matrix, as is the code to blend quaternions, but it will still fit in 
a shader model 2 vertex shader.

>  
> In the current solution I'm working with we keep the animation data as 
> quaternions and vectors (all transforms relative the parent) in order 
> to interpolate efficiently as well as perform blending operations. In 
> the end we still convert them into matrices, then do a full hierarchy 
> matrix mul before sending the matrices to the gpu.

We do the same thing, except we do the hierarchy multiplication in 
quaternions/offsets, and only convert to matrices when sending to the 
card (as 3x4 mats). It's a decent compromise.

Sincerely,

jw