[Sidefx-houdini-list] Quaternons and Lag CHOP

zhang xiao zhangxiao6776 at gmail.com
Thu Sep 1 13:25:04 EDT 2011


i think you need spherical interpolation for quaternions
http://theory.org/software/qfa/writeup/node12.html

2011/9/1 Pablo Giménez <pablogipi at gmail.com>

> Hi all.
> I am having some weird problems trying to apply some CHOPs to quaternion
> channels.
> I have a quaternion rot attribute (vector4).
> I read it using a Geometry CHOP as rot[xyzw] channels.
> Then I apply a Lag CHOP ( I have similar problems using Spring). Most of
> the
> rotations for my points works all right, except some of them, some points
> randomly at some frames just flip.
> Like if I werent using quaternions and you get the typical rotations
> flipping due to euler angles limitations.
> If I pass through the channels and import my rot attribute again without
> any
> effect it works, but as soon I apply a lag it gives me this random rotation
> flipping.
> If I change  the lag parameters then the flipping happens in other points
> at
> different frames.
> Really weird.
> Has anybody tried to lag rotations using chops?
> Thanks.
>
> --
> Un saludo
> Best Regards
> Pablo Giménez
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