patch from Dan Eicher with some edirts.

  vec.rotate(axis, angle)
equivalent to...
  vec[:] = vec * mathutils.Quaternion(axis, angle)

2 files changed, 32 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_math_vector.h b/source/blender/blenlib/BLI_math_vector.h
index 25f58787a43..215ddf2f2d9 100644
--- a/source/blender/blenlib/BLI_math_vector.h
+++ b/source/blender/blenlib/BLI_math_vector.h
@@ -148,6 +148,8 @@ void project_v3_v3v3(float r[3], const float p[3], const float n[3]);
 void reflect_v3_v3v3(float r[3], const float v[3], const float n[3]);
 void ortho_basis_v3v3_v3(float r1[3], float r2[3], const float a[3]);
 void bisect_v3_v3v3v3(float r[3], const float a[3], const float b[3], const float c[3]);
+void rotate_v3_v3v3fl(float v[3], const float p[3], const float axis[3], const float angle);
+void rotate_normalized_v3_v3v3fl(float v[3], const float p[3], const float axis[3], const float angle);
 
 /*********************************** Other ***********************************/
 
diff --git a/source/blender/blenlib/intern/math_vector.c b/source/blender/blenlib/intern/math_vector.c
index 04c8ae49dfa..e3cb5b37470 100644
--- a/source/blender/blenlib/intern/math_vector.c
+++ b/source/blender/blenlib/intern/math_vector.c
@@ -296,6 +296,36 @@ void ortho_basis_v3v3_v3(float v1[3], float v2[3], const float v[3])
 	}
 }
 
+/* Rotate a point p by angle theta around an arbitrary axis r
+   http://local.wasp.uwa.edu.au/~pbourke/geometry/
+*/
+void rotate_normalized_v3_v3v3fl(float r[3], const float p[3], const float axis[3], const float angle)
+{
+	const float costheta= cos(angle);
+	const float sintheta= sin(angle);
+
+	r[0]=	((costheta + (1 - costheta) * axis[0] * axis[0]) * p[0]) +
+			(((1 - costheta) * axis[0] * axis[1] - axis[2] * sintheta) * p[1]) +
+			(((1 - costheta) * axis[0] * axis[2] + axis[1] * sintheta) * p[2]);
+
+	r[1]=	(((1 - costheta) * axis[0] * axis[1] + axis[2] * sintheta) * p[0]) +
+			((costheta + (1 - costheta) * axis[1] * axis[1]) * p[1]) +
+			(((1 - costheta) * axis[1] * axis[2] - axis[0] * sintheta) * p[2]);
+
+	r[2]=	(((1 - costheta) * axis[0] * axis[2] - axis[1] * sintheta) * p[0]) +
+			(((1 - costheta) * axis[1] * axis[2] + axis[0] * sintheta) * p[1]) +
+			((costheta + (1 - costheta) * axis[2] * axis[2]) * p[2]);
+}
+
+void rotate_v3_v3v3fl(float r[3], const float p[3], const float axis[3], const float angle)
+{
+	float axis_n[3];
+
+	normalize_v3_v3(axis_n, axis);
+
+	rotate_normalized_v3_v3v3fl(r, p, axis_n, angle);
+}
+
 /*********************************** Other ***********************************/
 
 void print_v2(const char *str, const float v[2])