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Matrix Extraction for data

Started by webjeff Oct 20, 2005 at 2:46 PM 0 replies 550+ views

Original Post

Oct 20, 2005 at 2:46 PM

I am trying to extract 3d scale/position/rotation from a 4x4 transform matrix. Its easy enough to get the position vector. I think I have the rotation vector correctly, but someone who knows how to get all 3 vectors would be great. Any help would be appreciated. Especially because the scale is inheriently combined with the rotation components in the transform matrix. Any ideas would help. Jeff.

Zakwayda

1,120

Zakwayda

Oct 20, 2005 at 3:07 PM

I'm not sure what you mean by rotation vector, but assuming the matrix represents the sequence S->R->T, here's how to extract the info:

1. Position comes straight from translation vector (which you already know)
2. Scale factors are the lengths of the basis vectors (rows or columns of upper-left 3x3 matrix)
3. Divide basis vectors by scale factors to orthonormalize
4. Stop there, or convert basis vectors into something else (axis-angle, Euler angles, quat) if desired

Let us know if you need any clarification. Also, if you need more specific help perhaps you could tell us whether the matrix is in row- or column-vector form.

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