Thanks J.P. for all the help, this problem was starting to give me a headach.
For future refrence, this is how to get the correct angle of rotation about the
z-axis:
quat.getRotate(angle,axis);
double zAxisRotation = angle*axis.z();
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:osg-users-
> [EMAIL PROTECTED] On Behalf Of J.P. Delport
> Sent: 28. februar 2008 17:12
> To: OpenSceneGraph Users
> Subject: Re: [osg-users] Getting correct angles from osg::Matrixd in
> the 4'th Quadrant
>
> Hi,
>
> >> seems like the matrix.getrotate is broken again. 'osgunittests quat'
> >> also reports lots of problems.
> > sorry, I've spoken too soon. Matrix.getrotate is fine. The unittests
> > report false positives (q = -q is OK), will fix this.
> I promise to still fix the unittests...
>
> >
> > For your problem angles, quat(angle,axis) = -1 *
> osgTrans.getRotate(),
> > which is fine ito the rotation. It seems that quat.getRotate is the
> > culprit. Still looking...
> I was wrong again, quat.getRotate is also fine. The expectation (yours
> and mine) of what quat.getRotate(angle, axis) does was wrong.
>
> quat.getRotate _sets_ both the axis and angle. The axis is not a
> parameter in the sense of asking "What is the angle about this axis?",
> it is set by the call. If you print out the axis as well as the angle
> you will see that all is well, e.g. 271 deg about (0 0 -1) is the same
> as 89 about (0 0 1).
>
> I attach a modified version of your test.
>
> Sorry for all the noise, hope this clears it up.
>
> regards
> jp
>
> >
> > jp
> >
> >> I'm comparing with old working versions, will let you know.
> >>
> >> jp
> >>
> >> [EMAIL PROTECTED] wrote:
> >>> I've run into a problem using Quaternion rotation with osg::Matrixd
> that I can't seem to figure out. Consider the following test example
> and resulting output:
> >>>
> >>> #define DEG2RAD(d) d*(2*M_PI/360.0)
> >>> #define RAD2DEG(r) r*360.0/2*M_PI
> >>>
> >>> void testQuaternionRotation()
> >>> {
> >>> osg::Matrixd osgTrans;
> >>> osgTrans.set(osg::Matrix::identity());
> >>> osg::Vec3f axis(0.0,0.0,1.0);
> >>> double osgTransAngle,osgQuatAngle;
> >>>
> >>>
> >>> printf("\n*** Doing a 360 deg quaternion rotation about z-
> axis using OSG ***\n");
> >>> for(int i = 0; i < 360; ++i)
> >>> {
> >>> double angle = DEG2RAD(i);
> >>> osg::Quat quat(angle,axis);
> >>> quat.getRotate(osgQuatAngle,axis);
> >>>
> >>> //Set the quat rotation on matrix
> >>> osgTrans.setRotate(quat);
> >>> quat = osgTrans.getRotate();
> >>> quat.getRotate(osgTransAngle,axis);
> >>> printf("Rot: %.1f osgQang: %.1f osgTransAng:
> %.1f\n",RAD2DEG(angle),RAD2DEG(osgQuatAngle),RAD2DEG(osgTransAngle));
> >>> }
> >>> }
> >>>
> >>> Output:
> >>> Rot: 268.0 osgQang: 268.0 osgTransAng: 268.0
> >>> Rot: 269.0 osgQang: 269.0 osgTransAng: 269.0
> >>> Rot: 270.0 osgQang: 270.0 osgTransAng: 90.0
> >>> Rot: 271.0 osgQang: 271.0 osgTransAng: 89.0
> >>>
> >>> Reading back rotation angles in the 4'th quadrant gives me invalid
> values. I would have expected to either get negative angle or the angle
> that I used to rotate about the z-axis. Am I missing a elementary
> consept here or is this an actual bug in the implementation?
> >>> Setting the matrix using a quaternion with angles from the 4'th
> quaderant seems to be working just fine, it's only reading it back that
> doesn't work.
> >>>
> >>> Thanks for any help on this,
> >>> Filip
> >>> _______________________________________________
> >>> osg-users mailing list
> >>> [email protected]
> >>> http://lists.openscenegraph.org/listinfo.cgi/osg-users-
> openscenegrap
> >>> h.org
> >
>
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