public static Quaternion times(Quaternion result, Quaternion a, Quaternion b) {
result.w = (a.w * b.w) - (a.x * b.x) - (a.y * b.y) - (a.z * b.z);
result.x = (a.w * b.x) + (a.x * b.w) + (a.y * b.z) - (a.z * b.y);
result.y = (a.w * b.y) - (a.x * b.z) + (a.y * b.w) + (a.z * b.x);
result.z = (a.w * b.z) + (a.x * b.y) - (a.y * b.x) + (a.z * b.w);
return result;
}
/**
* http://ogre.sourcearchive.com/documentation/1.4.5/classOgre_1_1Vector3_eeef4472ad0c4d5f34a038a9f2faa819.html#eeef4472ad0c4d5f34a038a9f2faa819
*
* @param direction
* @return
*/
public Quaternion getRotationTo(Number3D direction) {
// Based on Stan Melax's article in Game Programming Gems
Quaternion q = new Quaternion();
// Copy, since cannot modify local
Number3D v0 = this;
Number3D v1 = direction;
v0.normalize();
v1.normalize();
float d = Number3D.dot(v0, v1);
// If dot == 1, vectors are the same
if (d >= 1.0f) {
q.setIdentity();
}
if (d < 0.000001f - 1.0f) {
// Generate an axis
Number3D axis = Number3D.cross(Number3D.getAxisVector(Axis.X), this);
if (axis.length() == 0) // pick another if colinear
axis = Number3D.cross(Number3D.getAxisVector(Axis.Y), this);
axis.normalize();
q.fromAngleAxis(MathUtil.radiansToDegrees(MathUtil.PI), axis);
} else {
float s = FloatMath.sqrt((1 + d) * 2);
float invs = 1f / s;
Number3D c = Number3D.cross(v0, v1);
q.x = c.x * invs;
q.y = c.y * invs;
q.z = c.z * invs;
q.w = s * 0.5f;
q.normalize();
}
return q;
}
public static Quaternion makeRotation(Quaternion result, float theta, Vector axis) {
float halfTheta = theta / 2;
float sinHalfTheta = GMath.sin(halfTheta);
result.w = GMath.cos(halfTheta);
result.x = axis.getX() * sinHalfTheta;
result.y = axis.getY() * sinHalfTheta;
result.z = axis.getZ() * sinHalfTheta;
return result;
}
