From 93a08fce17155addc14fc526644d9e24320d1a67 Mon Sep 17 00:00:00 2001
From: Recep Aslantas <info@recp.me>
Date: Mon, 9 Apr 2018 23:12:44 +0300
Subject: [PATCH] quat: axis angle of quaternion

---
 include/cglm/quat.h | 50 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/include/cglm/quat.h b/include/cglm/quat.h
index efea541..e73bf8b 100644
--- a/include/cglm/quat.h
+++ b/include/cglm/quat.h
@@ -260,6 +260,56 @@ glm_quat_imag(versor q, vec3 dest) {
   dest[2] = q[2];
 }
 
+/*!
+ * @brief returns normalized imaginary part of quaternion
+ *
+ * @param[in]   q    quaternion
+ */
+CGLM_INLINE
+void
+glm_quat_imagn(versor q, vec3 dest) {
+  glm_normalize_to(q, dest);
+}
+
+/*!
+ * @brief returns length of imaginary part of quaternion
+ *
+ * @param[in]   q    quaternion
+ */
+CGLM_INLINE
+float
+glm_quat_imaglen(versor q) {
+  return glm_vec_norm(q);
+}
+
+/*!
+ * @brief returns angle of quaternion
+ *
+ * @param[in]   q    quaternion
+ */
+CGLM_INLINE
+float
+glm_quat_angle(versor q) {
+  /*
+   sin(theta / 2) = length(x*x + y*y + z*z)
+   cos(theta / 2) = w
+   theta          = 2 * atan(sin(theta / 2) / cos(theta / 2))
+   */
+  return 2.0f * atan2f(glm_quat_imaglen(q), glm_quat_real(q));
+}
+
+/*!
+ * @brief axis of quaternion
+ *
+ * @param[in]   q    quaternion
+ * @param[out]  dest axis of quaternion
+ */
+CGLM_INLINE
+void
+glm_quat_axis(versor q, versor dest) {
+  glm_quat_imagn(q, dest);
+}
+
 /*!
  * @brief convert quaternion to mat4
  *