[osg-users] different result rotating Vec3d for Quat or Matrixd

[Trajce Nikolov NICK]

Hi,

> osg::Vec3d localEyeOffset2 = rotationMatrix * eyeOffset;

if you swap the order of the matrix and the vector will you get the same
result?

On Tue, Jan 24, 2017 at 11:25 AM, Gianni Ambrosio <g.ambrosio+osg at gmail.com>
wrote:

> Hi,
> may be this is a newbie question but I would like to understand the reason
> of this behaviour.
>
> I have to calculate the coordinate of a 3D point wrt a different
> coordinate reference. The new coordinate reference is simply rotated wrt
> the first one. I tried two different implementations with different results.
>
> osg::Vec3d eyeOffset(0.0, 0.0, 300.0);
> osg::Quat rotation(osg::DegreesToRadians(0.0), osg::Z_AXIS,
> osg::DegreesToRadians(0.0),  osg::Y_AXIS, osg::DegreesToRadians(45.0),
> osg::X_AXIS);
> osg::Vec3d localEyeOffset = rotation * eyeOffset;
> osg::Matrixd rotationMatrix(rotation);
> osg::Vec3d localEyeOffset2 = rotationMatrix * eyeOffset;
>
> I expected to have the same result for localEyeOffset and localEyeOffset2,
> while this is what I get:
> localEyeOffset is (0.0, -212.132, 212.132)
> localEyeOffset2 is (0.0, 212.132, 212.132)
>
> Can you explain me why?
>
> Regards,
> Gianni
>
> ------------------
> Read this topic online here:
> http://forum.openscenegraph.org/viewtopic.php?p=70034#70034
>
>
>
>
>
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-- 
trajce nikolov nick
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