Re: [ggt-devel] Quaternion bug?

[Kevin M. <ke...@vr...>]

well, you're making some assumtions based on euler to quat conversion 
(that it works).

try axis angle to quat, it is better tested I think.


On Wed, 12 Mar 2003, Justin Hare wrote:

> I think I may have found a problem with the multiplication of quaternions.
> 
>    // +90 degree rotation about the Y-axis
>    gmtl::Quatf quatA = gmtl::make<gmtl::Quatf>(gmtl::EulerAngleXYZf(0,gmtl::Math::deg2Rad(90.0), 0));
> 
>    // +90 degree rotation about the X-axis
>    gmtl::Quatf quatB = gmtl::make<gmtl::Quatf>(gmtl::EulerAngleXYZf(gmtl::Math::deg2Rad(90.0), 0, 0));
> 
>    // Starting with a point on the X-axis
>    gmtl::Point3f point( 1, 0, 0 );
> 
>    quatA *= quatB;
> 
>    point *= quatA;
> 
> Now the point should be pointing along the Y-axis, but it is actually (0,
> -1, 0), pointing straight down.
> 
> Is this a bug, or am I making some bad assumptions about how quaternion 
> multiplication should work?
> 
> justin
> 
> -----------------------------------------
> Justin Hare  <ja...@vr...>
> Virtual Reality Applications Center
> Iowa State University, Howe Hall
> http://www.vrac.iastate.edu/~jahare
> -----------------------------------------
> 
> 
> 
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