Matthias Ferch schrieb:
Andreas Goebel schrieb:
Matthias Ferch schrieb:
in my app, the user can enter 3 angles in degrees (float AngleX,
AngleY, AngleZ) in text controls to set the rotation of a
PositionAttitudeTransform. the entered values are then processed
like this:
float qx = (AngleX*PI)/180.0f;
float qy = (AngleY*PI)/180.0f;
float qz = (AngleX*PI)/180.0f;
MeshTransform->setAttitude( Quat(qx, Vec3(1.0f, 0.0f, 0.0f), qy,
Vec3(0.0f, 0.0f, 1.0f), -qz, Vec3(0.0f, 1.0f, 0.0f)) );
the user can alternativly simply rotate the
PositionAttitudeTransform with the mouse. so i need to get the
updated rotation values to update my text controls. my question is
now, how can i extract these values back from the transform (in
degrees)? yeah i suck at maths :D
thanks in advance!
_______________________________________________
Hi,
it´s not that easy and no shame to ask.
I have the nice book "Geometric toosl for computer graphics", and
there is the following solution:
- convert the quat to a matrix. Lets assume your matrix is r00, r01,
r02 (first row), r10, r11, r12 (second row) and so on (convert this
to your needs)
thetaY = asin(r02);
if (thetaY < PI/2.0) {
if (thetaY > -PI /2.0) {
thetaX = atan2(-r12, r22);
thetaZ = atan2(-r01, r00);
} else{
//solution is not unique!
thetaX = -atan2(r10, r11);
thetaZ = 0;
}
}else{
thetaX = atan2(r10, r11);
thetaZ = 0;
}
atan2 is defined in math.h
Please let me know if it works. You will have to calculate back the
values do degrees, of yourse. The solution is not unique, and I don´t
know if you have the ordering x, y, z.
Regards,
Andreas
oha ok, thank you! one problem though, i created a matrix from the
quat, but how can i access the members of a matrix in osg? the []
operator is not defined..
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ok, i got it like this now:
osg::Quat attitude =
parent_data->MeshTransform->getAttitude();
osg::Matrix matrix = osg::Matrix( attitude );
float r02 = matrix(0, 2);
float r12 = matrix(1, 2);
float r22 = matrix(2, 2);
float r01 = matrix(0, 1);
float r00 = matrix(0, 0);
float r10 = matrix(1, 0);
float r11 = matrix(1, 1);
float thetaX, thetaY, thetaZ;
thetaY = asin( r02 );
if( thetaY < PI/2.0 )
{
if( thetaY > -PI/2.0 )
{
thetaX = atan2( -r12, r22 );
thetaZ = atan2( -r01, r00 );
}
else
{
thetaX = -atan2( r10, r11 );
thetaZ = 0;
}
}
else
{
thetaX = atan2( r10, r11 );
thetaZ = 0;
}
VectorX->SetValue( -(thetaX*180.0f)/PI ); // why do
i need a minus here?
VectorY->SetValue( -(thetaZ*180.0f)/PI );
VectorZ->SetValue( (thetaY*180.0f)/PI );)
does this look reasonable? well, it works correctly, if i enter values
for VectorX and VectorY, but keep VectorZ = 0.0f. it also works if I
enter a value for VectorZ, but keep VectorX = 0.0 and VectorZ = 0.0. but
as soon as enter values for VectorZ and either ValueX or ValueY, the
values are not given back correctly. trotzdem vielen dank schonmal :P
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