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
--
Andreas Goebel
Visit http://www.raumgeometrie.de to take a look at
Archimedes Geo3D, a program for dynamic geometry
in three dimensions!
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