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# [QUATERNION] right handed to left handed

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### #1Alundra  Members   -  Reputation: 929

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Posted 07 July 2013 - 07:13 AM

Hi all,

I convert my quaternion to a matrix using left handed coord system.

I have an input who is right handed, so the rotation needs to be inverted on each axis.

When I input my quaternion, if I change w to -w it's ok, inverted axis works too.

What is the more correct, invert the w or invert (x,y,z) ?

Thanks

Edited by Alundra, 07 July 2013 - 07:15 AM.

### #2Paradigm Shifter  Crossbones+   -  Reputation: 5439

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Posted 07 July 2013 - 07:47 AM

It's the same. q and -q both represent the same rotation (although if you interpolate you need to make sure the [4d] dot-product of the quaternions you interpolate between dot(q0, q1) is > 0 to go the short way round (i.e. less than 180 degrees)).

"Most people think, great God will come from the sky, take away everything, and make everybody feel high" - Bob Marley

### #3Alundra  Members   -  Reputation: 929

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Posted 07 July 2013 - 12:15 PM

-q = ( -x, -y; -z; -w )

all components of the quaternion are inverted.
I was talking about just changing the real or the imaginary part of the quaternion.

### #4Paradigm Shifter  Crossbones+   -  Reputation: 5439

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Posted 07 July 2013 - 12:25 PM

No, you were asking whether

q = (x, y, z, -w)

was more correct than

-q = (-x, -y, -z, w)

the answer is neither: they both represent the same rotation/orientation.

Edited by Paradigm Shifter, 07 July 2013 - 12:33 PM.

"Most people think, great God will come from the sky, take away everything, and make everybody feel high" - Bob Marley

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