Fix T38358: Face snapping fails on Orthographic view

Issue is caused by start point of ray used to detect faces under the mouse is set rather far away in ortho 3dviews.
The loss of precision on the ray location induced by this can lead to face snapping failures.

Solution is to do the raycasting with a temp start point, much closer to the object we check, and add back
to the found distance the diff to the real start point once detection is done (as we need all hit distances
from all tested objects to be relative to a common point!).

Note this commit only addresses the "face snapping on mesh" case, other kind of snapping do not seem to suffer
from this issue.

Reviewers: brecht, campbellbarton

Differential Revision: https://developer.blender.org/D268

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 f155247f851..a76c904acdd 100644
--- a/source/blender/editors/include/ED_view3d.h
+++ b/source/blender/editors/include/ED_view3d.h
@@ -200,6 +200,8 @@ eV3DProjStatus ED_view3d_project_float_object(const struct ARegion *ar, const fl
 float ED_view3d_calc_zfac(const struct RegionView3D *rv3d, const float co[3], bool *r_flip);
 bool ED_view3d_win_to_ray(const struct ARegion *ar, struct View3D *v3d, const float mval[2],
                           float ray_start[3], float ray_normal[3], const bool do_clip);
+bool ED_view3d_win_to_ray_ex(const struct ARegion *ar, struct View3D *v3d, const float mval[2],
+                             float r_ray_co[3], float r_ray_normal[3], float r_ray_start[3], bool do_clip);
 void ED_view3d_global_to_vector(const struct RegionView3D *rv3d, const float coord[3], float vec[3]);
 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]);