/**
* Returns a tangent Quaternion for {@code center}, defined by {@code before} and {@code after}
* quaternions.
*
* @param before the first Quaternion
* @param center the second Quaternion
* @param after the third Quaternion
*/
public static final Quaternion squadTangent(
Quaternion before, Quaternion center, Quaternion after) {
Quaternion l1 = Quaternion.lnDif(center, before);
Quaternion l2 = Quaternion.lnDif(center, after);
Quaternion e = new Quaternion();
e.x = -0.25f * (l1.x + l2.x);
e.y = -0.25f * (l1.y + l2.y);
e.z = -0.25f * (l1.z + l2.z);
e.w = -0.25f * (l1.w + l2.w);
return Quaternion.multiply(center, e.exp());
}
