quat_mul - Man Page

#include <allegro.h>

void quat_mul(const QUAT *p, const QUAT *q, QUAT *out);

Multiplies two quaternions, storing the result in out. The resulting  quaternion will have the same effect as the combination of p and q, ie.  when applied to a point, (point * out) = ((point * p) * q). Any number of  rotations can be concatenated in this way. Note that quaternion  multiplication is not commutative, ie. quat_mul(p, q) != quat_mul(q, p).