Use BLI_bvhtree_walk_dfs for snapping

The snapping functions when performed in the perspective view,
have some problems in the threshold (a distortion) and in the clip plane (the normal is incorrect).
These problems can be only observed when making the snap to edges or to vertices (nearest to ray function).

This patch propose a totally different solution.
The idea is to project the edges of bvh nodes and test the 2d projection of the snap element.

For this it used the BLI_bvhtree_walk_dfs function.

It is important to pay particular attention also to the changes in `ED_transform_snap_object_project_view3d_ex`

1 files changed, 2 insertions, 0 deletions

diff --git a/source/blender/editors/include/ED_view3d.h b/source/blender/editors/include/ED_view3d.h
index b09284aa759..48c1e2d1996 100644
--- a/source/blender/editors/include/ED_view3d.h
+++ b/source/blender/editors/include/ED_view3d.h
@@ -208,6 +208,7 @@ eV3DProjStatus ED_view3d_project_float_global(const struct ARegion *ar, const fl
 eV3DProjStatus ED_view3d_project_float_object(const struct ARegion *ar, const float co[3], float r_co[2], const eV3DProjTest flag);
 
 float ED_view3d_calc_zfac(const struct RegionView3D *rv3d, const float co[3], bool *r_flip);
+bool ED_view3d_clip_segment(const struct RegionView3D *rv3d, float ray_start[3], float ray_end[3]);
 bool ED_view3d_win_to_ray(
         const struct ARegion *ar, const struct View3D *v3d, const float mval[2],
         float ray_start[3], float ray_normal[3], const bool do_clip);
@@ -218,6 +219,7 @@ void ED_view3d_global_to_vector(const struct RegionView3D *rv3d, const float coo
 void ED_view3d_win_to_3d(const struct ARegion *ar, const float depth_pt[3], const float mval[2], float out[3]);
 void ED_view3d_win_to_3d_int(const struct ARegion *ar, const float depth_pt[3], const int mval[2], float out[3]);
 void ED_view3d_win_to_delta(const struct ARegion *ar, const float mval[2], float out[3], const float zfac);
+void ED_view3d_win_to_origin(const struct ARegion *ar, const float mval[2], float out[3]);
 void ED_view3d_win_to_vector(const struct ARegion *ar, const float mval[2], float out[3]);
 bool ED_view3d_win_to_segment(const struct ARegion *ar, struct View3D *v3d, const float mval[2],
                               float r_ray_start[3], float r_ray_end[3], const bool do_clip);