/**
* @ingroup quaternion
* @brief Given two vectors, find a quaternion that will get you from one to the other
*
* @param from the starting vector
* @param to the ending vector
* @param qR the resulting quaternion that gets you from the starting vector to the ending vector
*/
HYPAPI quaternion * quaternion_get_rotation_tov3(const vector3 *from, const vector3 *to, quaternion *qR)
{
/* this code avoids sqrt and cos and sin and would be nice to avoid division */
vector3 w;
float dot;
float norm;
vector3_cross_product(&w, from, to);
dot = vector3_dot_product(from, to);
qR->x = w.x;
qR->y = w.y;
qR->z = w.z;
qR->w = dot;
norm = quaternion_norm(qR);
qR->w += norm;
/* normalization with avoidance of div/0 and reusing the norm (already calculated above) */
if(norm != 0)
{
qR->x /= norm;
qR->y /= norm;
qR->z /= norm;
qR->w /= norm;
}
return qR;
}
static char *test_vector3_cross_product(void)
{
struct vector3 a;
struct vector3 b;
struct vector3 r;
vector3_setf3(&a, 3.0f, -3.0f, 1.0f);
vector3_setf3(&b, 4.0f, 9.0f, 2.0f);
vector3_cross_product(&r, &a, &b);
test_assert(scalar_equalsf(r.x, -15.0f));
test_assert(scalar_equalsf(r.y, -2.0f));
test_assert(scalar_equalsf(r.z, 39.0f));
/* tests lack of commutative property */
vector3_cross_product(&r, &b, &a);
test_assert(!scalar_equalsf(r.x, -15.0f));
test_assert(!scalar_equalsf(r.y, -2.0f));
test_assert(!scalar_equalsf(r.z, 39.0f));
return 0;
}
/**
* @ingroup vector3
* @brief finds the vector describing the normal between two vectors
*
*/
HYPAPI vector3 *vector3_find_normal_axis_between(vector3 *vR, const vector3 *vT1, const vector3 *vT2)
{
vector3_cross_product(vR, vT1, vT2);
vector3_normalize(vR);
return vR;
}
