/**
* graphene_quaternion_to_angle_vec3:
* @q: a #graphene_quaternion_t
* @angle: (out): return location for the angle, in degrees
* @axis: (out caller-allocates): return location for the rotation axis
*
* Converts a quaternion into an @angle, @axis pair.
*
* Since: 1.0
*/
void
graphene_quaternion_to_angle_vec3 (const graphene_quaternion_t *q,
float *angle,
graphene_vec3_t *axis)
{
graphene_quaternion_t q_n;
float cos_a;
graphene_quaternion_normalize (q, &q_n);
cos_a = q_n.w;
if (angle != NULL)
*angle = GRAPHENE_RAD_TO_DEG (acosf (cos_a) * 2.f);
if (axis != NULL)
{
float sin_a = sqrtf (1.f - cos_a * cos_a);
if (fabsf (sin_a) < 0.00005)
sin_a = 1.f;
graphene_vec3_init (axis, q_n.x / sin_a, q_n.y / sin_a, q_n.z / sin_a);
}
}
/**
* graphene_quaternion_to_angles:
* @q: a #graphene_quaternion_t
* @deg_x: (out) (optional): return location for the rotation angle on
* the X axis (yaw), in degress
* @deg_y: (out) (optional): return location for the rotation angle on
* the Y axis (pitch), in degrees
* @deg_z: (out) (optional): return location for the rotation angle on
* the Z axis (roll), in degrees
*
* Converts a #graphene_quaternion_t to its corresponding rotations
* on the [Euler angles](http://en.wikipedia.org/wiki/Euler_angles)
* on each axis.
*
* Since: 1.2
*/
void
graphene_quaternion_to_angles (const graphene_quaternion_t *q,
float *deg_x,
float *deg_y,
float *deg_z)
{
graphene_vec4_t v;
graphene_vec4_t sq;
float qx, qy, qz, qw, sqx, sqy, sqz, sqw;
graphene_quaternion_to_vec4 (q, &v);
graphene_vec4_multiply (&v, &v, &sq);
qx = graphene_vec4_get_x (&v);
qy = graphene_vec4_get_y (&v);
qz = graphene_vec4_get_z (&v);
qw = graphene_vec4_get_w (&v);
sqx = graphene_vec4_get_x (&sq);
sqy = graphene_vec4_get_y (&sq);
sqz = graphene_vec4_get_z (&sq);
sqw = graphene_vec4_get_w (&sq);
if (deg_x != NULL)
{
float res = atan2f (2 * (qx * qw - qy * qz), (sqw - sqx - sqy + sqz));
*deg_x = GRAPHENE_RAD_TO_DEG (res);
}
if (deg_y != NULL)
{
float res = asinf (CLAMP (2 * ( qx * qz + qy * qw), -1, 1));
*deg_y = GRAPHENE_RAD_TO_DEG (res);
}
if (deg_z != NULL)
{
float res = atan2f (2 * (qz * qw - qx * qy), (sqw + sqx - sqy - sqz));
*deg_z = GRAPHENE_RAD_TO_DEG (res);
}
}
/**
* graphene_euler_get_z:
* @e: a #graphene_euler_t
*
* Retrieves the rotation angle on the Z axis, in degrees.
*
* Returns: the rotation angle
*
* Since: 1.2
*/
float
graphene_euler_get_z (const graphene_euler_t *e)
{
return GRAPHENE_RAD_TO_DEG (graphene_vec3_get_z (&e->angles));
}
