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

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)).

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

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.