Optimization: use `BLI_bvhtree_intersect_plane` to detect faces that will be affected by the knife tool

The knife code currently calls the `BLI_bvhtree_overlap` function that
tests the overlap between the mesh tree and an AABB that encompasses the
points projected in the clip_start, clip_end and or clip_planes of the
view.

This resulted in many false positives since the AABB is very large.
Often all the triangles "overlapped".

The solution was to create a new function that actually tests the
intersection of AABB with a plane.

Even not considering the clip_planes of the view, this solution is more
appropriate than using overlap.

Differential Revision: https://developer.blender.org/D8229

1 files changed, 2 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_kdopbvh.h b/source/blender/blenlib/BLI_kdopbvh.h
index 70fa633eeac..9e4e30181b9 100644
--- a/source/blender/blenlib/BLI_kdopbvh.h
+++ b/source/blender/blenlib/BLI_kdopbvh.h
@@ -174,6 +174,8 @@ BVHTreeOverlap *BLI_bvhtree_overlap(const BVHTree *tree1,
                                     BVHTree_OverlapCallback callback,
                                     void *userdata);
 
+int *BLI_bvhtree_intersect_plane(BVHTree *tree, float plane[4], uint *r_intersect_tot);
+
 int BLI_bvhtree_get_len(const BVHTree *tree);
 int BLI_bvhtree_get_tree_type(const BVHTree *tree);
 float BLI_bvhtree_get_epsilon(const BVHTree *tree);