+static inline
+float
+deg2rad(const float degree)
+{
+ return( degree * 0.017453292519943295769236907684886F);
+}
+
+static inline void
+rotate_xy(float* mat3, const float degreesAroundX, const float degreesAroundY)
+{
+ const float rad1 = deg2rad(degreesAroundX);
+ const float c1 = cosf(rad1);
+ const float s1 = sinf(rad1);
+ const float rad2 = deg2rad(degreesAroundY);
+ const float c2 = cosf(rad2);
+ const float s2 = sinf(rad2);
+ mat3[0] = c2; mat3[3] = 0.0F; mat3[6] = s2;
+ mat3[1] = s1*s2; mat3[4] = c1; mat3[7] = -s1*c2;
+ mat3[2] = -c1*s2;mat3[5] = s1; mat3[8] = c1*c2;
+}
+
+static inline void
+identity(float* mat3)
+{
+ mat3[0] = 1.0F; mat3[3] = 0.0F; mat3[6] = 0.0F;
+ mat3[1] = 0.0F; mat3[4] = 1.0F; mat3[7] = 0.0F;
+ mat3[2] = 0.0F; mat3[5] = 0.0F; mat3[8] = 1.0F;
+}