barycentric transform utility geometry function.

From 2 triangles and 1 point, the relative position between the point and the first triangle is applied to the second triangle to find the target point.
the barycentric weights are calculated in 2D space with a signed area so values outside the triangle bounds are supported.

wrapped by python:
 pt_to = Geometry.BarycentricTransform(pt_from, t1a, t1b, t1c, t2a, t1b, t1c)

NOTE: 
- moved some barycentric weight functions out of projection painting into the math lib.
- ended up making some of the math functions use const args.
TODO:
- support exceptional cases. zero area tries and similar.

1 files changed, 2 insertions, 1 deletions

diff --git a/source/blender/blenlib/BLI_math_rotation.h b/source/blender/blenlib/BLI_math_rotation.h
index b221d89487f..b640cf6dc3c 100644
--- a/source/blender/blenlib/BLI_math_rotation.h
+++ b/source/blender/blenlib/BLI_math_rotation.h
@@ -70,7 +70,8 @@ void mat3_to_quat(float q[4], float mat[3][3]);
 void mat4_to_quat(float q[4], float mat[4][4]);
 void tri_to_quat(float q[4], float a[3], float b[3], float c[3]);
 void vec_to_quat(float q[4], float vec[3], short axis, short upflag);
-void rotation_between_vecs_to_quat(float q[4], float v1[3], float v2[3]);
+/* note: v1 and v2 must be normalized */
+void rotation_between_vecs_to_quat(float q[4], const float v1[3], const float v2[3]);
 
 /* TODO: don't what this is, but it's not the same as mat3_to_quat */
 void mat3_to_quat_is_ok(float q[4], float mat[3][3]);