quat: quaternion to mat3

include/cglm/call/quat.h

@@ -51,6 +51,10 @@ CGLM_EXPORT
 void
 glmc_quat_mat4(versor q, mat4 dest);
 
+CGLM_EXPORT
+void
+glmc_quat_mat3(versor q, mat3 dest);
+
 CGLM_EXPORT
 void
 glmc_quat_slerp(versor q,

include/cglm/quat.h

@@ -216,6 +216,42 @@ glm_quat_mat4(versor q, mat4 dest) {
   dest[3][3] = 1.0f;
 }
 
+/*!
+ * @brief convert quaternion to mat3
+ *
+ * @param[in]   q     quaternion
+ * @param[out]  dest  result matrix
+ */
+CGLM_INLINE
+void
+glm_quat_mat3(versor q, mat3 dest) {
+  float w, x, y, z;
+  float xx, yy, zz;
+  float xy, yz, xz;
+  float wx, wy, wz;
+
+  w = q[0];
+  x = q[1];
+  y = q[2];
+  z = q[3];
+
+  xx = 2.0f * x * x;   xy = 2.0f * x * y;   wx = 2.0f * w * x;
+  yy = 2.0f * y * y;   yz = 2.0f * y * z;   wy = 2.0f * w * y;
+  zz = 2.0f * z * z;   xz = 2.0f * x * z;   wz = 2.0f * w * z;
+
+  dest[0][0] = 1.0f - yy - zz;
+  dest[1][1] = 1.0f - xx - zz;
+  dest[2][2] = 1.0f - xx - yy;
+
+  dest[0][1] = xy + wz;
+  dest[1][2] = yz + wx;
+  dest[2][0] = xz + wy;
+
+  dest[1][0] = xy - wz;
+  dest[2][1] = yz - wx;
+  dest[0][2] = xz - wy;
+}
+
 /*!
  * @brief interpolates between two quaternions
  *        using spherical linear interpolation (SLERP)

src/quat.c

@@ -62,6 +62,12 @@ glmc_quat_mat4(versor q, mat4 dest) {
   glm_quat_mat4(q, dest);
 }
 
+CGLM_EXPORT
+void
+glmc_quat_mat3(versor q, mat3 dest) {
+  glm_quat_mat3(q, dest);
+}
+
 CGLM_EXPORT
 void
 glmc_quat_slerp(versor q,