Math Lib: add project_plane_v3_v3v3

Useful for projecting one vector onto another (as a plane).

This is a rather common operation,
doing inline isn't always obvious whats happening.

1 files changed, 21 insertions, 0 deletions

diff --git a/source/blender/blenlib/intern/math_vector.c b/source/blender/blenlib/intern/math_vector.c
index 814180bba24..e9909cef29d 100644
--- a/source/blender/blenlib/intern/math_vector.c
+++ b/source/blender/blenlib/intern/math_vector.c
@@ -572,6 +572,27 @@ void project_v3_v3v3(float c[3], const float v1[3], const float v2[3])
 	c[2] = mul * v2[2];
 }
 
+/**
+ * In this case plane is a 3D vector only (no 4th component).
+ *
+ * Projecting will make \a c a copy of \a v orthogonal to \a v_plane.
+ *
+ * \note If \a v is exactly perpendicular to \a v_plane, \a c will just be a copy of \a v.
+ */
+void project_plane_v3_v3v3(float c[3], const float v[3], const float v_plane[3])
+{
+	float delta[3];
+	project_v3_v3v3(delta, v, v_plane);
+	sub_v3_v3v3(c, v, delta);
+}
+
+void project_plane_v2_v2v2(float c[2], const float v[2], const float v_plane[2])
+{
+	float delta[2];
+	project_v2_v2v2(delta, v, v_plane);
+	sub_v2_v2v2(c, v, delta);
+}
+
 /* project a vector on a plane defined by normal and a plane point p */
 void project_v3_plane(float v[3], const float n[3], const float p[3])
 {