Mesh: minor optimization to concave quad check for tessellation

Use the face normal (when available) for a faster concave quad test.

2 files changed, 18 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_math_geom.h b/source/blender/blenlib/BLI_math_geom.h
index c744c5d13d3..49188964f3b 100644
--- a/source/blender/blenlib/BLI_math_geom.h
+++ b/source/blender/blenlib/BLI_math_geom.h
@@ -105,6 +105,11 @@ bool is_quad_flip_v3_first_third_fast(const float v1[3],
                                       const float v2[3],
                                       const float v3[3],
                                       const float v4[3]);
+bool is_quad_flip_v3_first_third_fast_with_normal(const float v1[3],
+                                                  const float v2[3],
+                                                  const float v3[3],
+                                                  const float v4[3],
+                                                  const float normal[3]);
 
 /********************************* Distance **********************************/
 
diff --git a/source/blender/blenlib/intern/math_geom.c b/source/blender/blenlib/intern/math_geom.c
index 6b1730f8ee8..0a5dc8517d8 100644
--- a/source/blender/blenlib/intern/math_geom.c
+++ b/source/blender/blenlib/intern/math_geom.c
@@ -6218,6 +6218,19 @@ bool is_quad_flip_v3_first_third_fast(const float v1[3],
   return dot_v3v3(cross_a, cross_b) > 0.0f;
 }
 
+bool is_quad_flip_v3_first_third_fast_with_normal(const float v1[3],
+                                                  const float v2[3],
+                                                  const float v3[3],
+                                                  const float v4[3],
+                                                  const float normal[3])
+{
+  float dir_v3v1[3], tangent[3];
+  sub_v3_v3v3(dir_v3v1, v3, v1);
+  cross_v3_v3v3(tangent, dir_v3v1, normal);
+  const float dot = dot_v3v3(v1, tangent);
+  return (dot_v3v3(v4, tangent) >= dot) || (dot_v3v3(v2, tangent) <= dot);
+}
+
 /**
  * Return the value which the distance between points will need to be scaled by,
  * to define a handle, given both points are on a perfect circle.