I need some pointers on how to implement billboarded meshes, especially when in a bone hiearchy. I've managed to build a matrix that compensates for the camera's angle, but whenever a parent bone rotates it is no longer properly billboarded. How do you sovle this? I've thought of decomposing the parent matrix and performing an inverse rotation to compensate for this. Is this correct? I've had no luck finding docs on this subject (note: meshes, not simple sprite billboards!). Links are welcome!

I would transform the midpoint of the billboard using the skeleton, and then generate the actual billboard geometry separately using the camera up/right vectors, at that transformed point.

I doubt you read my post as I stated that:

1) I use meshes, and NOT sprite billboards
2) I already have a matrix that compensates for the camera rotation

Also, say I have a generic rotation matrix. Is there a way to extract how much it rotates around a specific axis?

Like: M = M_around_z * M_rest

(I want M_around_z, or more specifically the angle it rotates around z).