/**
* Performs a great circle interpolation between quaternion q1 and quaternion q2 and places the
* result into this quaternion.
*
* @param q1 the first quaternion
* @param q2 the second quaternion
* @param alpha the alpha interpolation parameter
*/
public final void interpolate(Quat4f q1, Quat4f q2, float alpha) {
// From "Advanced Animation and Rendering Techniques"
// by Watt and Watt pg. 364, function as implemented appeared to be
// incorrect. Fails to choose the same quaternion for the double
// covering. Resulting in change of direction for rotations.
// Fixed function to negate the first quaternion in the case that the
// dot product of q1 and this is negative. Second case was not needed.
double dot, s1, s2, om, sinom;
dot = q2.x * q1.x + q2.y * q1.y + q2.z * q1.z + q2.w * q1.w;
if (dot < 0) {
// negate quaternion
q1.x = -q1.x;
q1.y = -q1.y;
q1.z = -q1.z;
q1.w = -q1.w;
dot = -dot;
}
if ((1.0 - dot) > 0.000001f) {
om = Math.acos(dot);
sinom = Math.sin(om);
s1 = Math.sin((1.0 - alpha) * om) / sinom;
s2 = Math.sin(alpha * om) / sinom;
} else {
s1 = 1.0 - alpha;
s2 = alpha;
}
w = (float) (s1 * q1.w + s2 * q2.w);
x = (float) (s1 * q1.x + s2 * q2.x);
y = (float) (s1 * q1.y + s2 * q2.y);
z = (float) (s1 * q1.z + s2 * q2.z);
}
protected void moveOrientation() {
if (Camera.host != owner || !PerfIO.holdMouse) return;
AxisAngle4f tmp = new AxisAngle4f(Camera.right, -PerfIO.dy * 0.001f);
Quat4f rot = new Quat4f();
rot.set(tmp);
owner.getOrientWritable().mul(rot, owner.getOrientation());
owner.getOrientWritable().normalize();
tmp.set(0, Camera.up.y > 0 ? 1 : -1, 0, PerfIO.dx * 0.001f);
rot.set(tmp);
owner.getOrientWritable().mul(rot, owner.getOrientWritable());
owner.flushChanges();
}
