// using vDown, vNow, dragging, and axisSet, compute rotations
void ArcBall::update ()
{
int setSize = setSizes[axisSet];
Quat *set = (Quat *)(sets[axisSet]);
vFrom = mouseOnSphere(vDown, center, radius);
vTo = mouseOnSphere(vNow, center, radius);
if(dragging)
{
if(axisSet != NoAxes)
{
vFrom = constrainToAxis(vFrom, set[axisIndex]);
vTo = constrainToAxis(vTo, set[axisIndex]);
}
qDrag = fromBallPoints(vFrom, vTo);
qNow = qDrag * qDown;
}
else if(axisSet != NoAxes)
axisIndex = nearestConstraintAxis(vTo, set, setSize);
toBallPoints(qDown, vrFrom, vrTo);
getRotation(qNow.conjugate(), mNow); // gives transpose to OpenGL
}
//------------------------------------------------------------------------------
void ArcBall::drag(const glm::vec2& msc)
{
// Regular drag code to follow...
mVNow = (mScreenToTCS * glm::vec4(msc.x, msc.y, 0.0, 1.0)).xyz();
mVSphereFrom= mouseOnSphere(mVDown);
mVSphereTo = mouseOnSphere(mVNow);
// Construct a quaternion from two points on the unit sphere.
mQDrag = quatFromUnitSphere(mVSphereFrom, mVSphereTo);
mQNow = mQDrag * mQDown;
// Perform complex conjugate
glm::quat q = mQNow;
q.x = -q.x;
q.y = -q.y;
q.z = -q.z;
q.w = q.w;
mMatNow = glm::mat4_cast(q);
}