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MPM | Deformation gradient F to orientation

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sanostol
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Joined: 11月 2005
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Hello,
how can I extract only the orientation from this matrix , without shear and scale? The quaternion function seems not to ignore the scales and shears that are stored in the matrix and this leads to different rotations.

I get strange mblur result when I try te calclate the w attribute from this.
thanks
Martin
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animatrix_
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Joined: 2月 2012
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Hi Martin,

You can do this using the polardecomp [www.sidefx.com] VEX function:

matrix3 R, S;
polardecomp ( F, R, S );
vector4 q = quaternion ( R );
Senior FX TD @ Industrial Light & Magic
Get to the NEXT level in Houdini & VEX with Pragmatic VEX! [www.pragmatic-vfx.com] https://lnk.bio/animatrix [lnk.bio]
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sanostol
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thank You, as always a helping hand
Edited by sanostol - 2025年4月17日 05:59:13
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