SkinWeights and Offset Matrix in .X File

SkinWeights and Offset Matrix in .X File

Post by b.. » Thu, 17 Oct 2002 20:28:12



I'm wondering if someone can elaborate on the Offset Matrix found in
the SkinWeights template in the .X file format.

Here's my problem:

I want to be able to transform the bones back to their "original" pose
(ie. the position which was used to weight the mesh). But the .X file
format stores the bone's transformation matrix already transformed by
the animation but the mesh is stored untransformed.

if you take the .X file in the skinmesh example (Tiny.x) for example.
The mesh's position is untransformed (it's in a classic DaVinci pose)
but the bones are transformed to the first frame of the animation!

So I guess the matrix offset can be used to transform the bone back to
their original "Da Vinci" pose also... but I'm not sure how to do
this... can't make heads or tail of what it contains.

tx
Dom

 
 
 

SkinWeights and Offset Matrix in .X File

Post by Craig Peeper [MS » Sun, 27 Oct 2002 01:49:40


If you want the "base" pose, set all the frame matrices to identity.  This
should result in the figure pose of the model that is stored in the vertex
buffer.

--
Craig Peeper
Microsoft, Direct3D

This posting is provided "AS IS" with no warranties, and confers no rights.

Quote:> I'm wondering if someone can elaborate on the Offset Matrix found in
> the SkinWeights template in the .X file format.

> Here's my problem:

> I want to be able to transform the bones back to their "original" pose
> (ie. the position which was used to weight the mesh). But the .X file
> format stores the bone's transformation matrix already transformed by
> the animation but the mesh is stored untransformed.

> if you take the .X file in the skinmesh example (Tiny.x) for example.
> The mesh's position is untransformed (it's in a classic DaVinci pose)
> but the bones are transformed to the first frame of the animation!

> So I guess the matrix offset can be used to transform the bone back to
> their original "Da Vinci" pose also... but I'm not sure how to do
> this... can't make heads or tail of what it contains.

> tx
> Dom


 
 
 

1. Matrix contents of the SkinWeights section in a .X file

I have been examining the contents of a .X file.  The "SkinWeights"
section of the mesh has a matrix specified at the end.  I would like
to convert this matrix to a quaternion and offset vector but I cannot
because the matrix is not a simple rotation/translation matrix.

What I would like to know is what is the content of these matrices so
that I might properly decompose it.

Thanks
Murrgon

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