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, 35 insertions, 20 deletions

diff --git a/source/blender/editors/space_view3d/view3d_project.c b/source/blender/editors/space_view3d/view3d_project.c
index ac05853e6d0..e6d8bdcf50f 100644
--- a/source/blender/editors/space_view3d/view3d_project.c
+++ b/source/blender/editors/space_view3d/view3d_project.c
@@ -312,25 +312,9 @@ static void view3d_win_to_ray_segment(
 	if (!r_ray_co) r_ray_co = _ray_co;
 	if (!r_ray_dir) r_ray_dir = _ray_dir;
 
+	ED_view3d_win_to_origin(ar, mval, r_ray_co);
 	ED_view3d_win_to_vector(ar, mval, r_ray_dir);
 
-	if (rv3d->is_persp) {
-		copy_v3_v3(r_ray_co, rv3d->viewinv[3]);
-	}
-	else {
-		r_ray_co[0] = 2.0f * mval[0] / ar->winx - 1.0f;
-		r_ray_co[1] = 2.0f * mval[1] / ar->winy - 1.0f;
-
-		if (rv3d->persp == RV3D_CAMOB) {
-			r_ray_co[2] = -1.0f;
-		}
-		else {
-			r_ray_co[2] = 0.0f;
-		}
-
-		mul_project_m4_v3(rv3d->persinv, r_ray_co);
-	}
-
 	if ((rv3d->is_persp == false) && (rv3d->persp != RV3D_CAMOB)) {
 		end_offset = v3d->far / 2.0f;
 		start_offset = -end_offset;
@@ -347,7 +331,7 @@ static void view3d_win_to_ray_segment(
 	}
 }
 
-BLI_INLINE bool view3d_clip_segment(const RegionView3D *rv3d, float ray_start[3], float ray_end[3])
+bool ED_view3d_clip_segment(const RegionView3D *rv3d, float ray_start[3], float ray_end[3])
 {
 	if ((rv3d->rflag & RV3D_CLIPPING) &&
 	    (clip_segment_v3_plane_n(ray_start, ray_end, rv3d->clip, 6,
@@ -384,7 +368,7 @@ bool ED_view3d_win_to_ray_ex(
 
 	/* bounds clipping */
 	if (do_clip) {
-		return view3d_clip_segment(ar->regiondata, r_ray_start, ray_end);
+		return ED_view3d_clip_segment(ar->regiondata, r_ray_start, ray_end);
 	}
 
 	return true;
@@ -549,6 +533,37 @@ void ED_view3d_win_to_delta(const ARegion *ar, const float mval[2], float out[3]
 }
 
 /**
+ * Calculate a 3d origin from 2d window coordinates.
+ * \note Orthographic views have a less obvious origin,
+ * Since far clip can be a very large value resulting in numeric precision issues,
+ * the origin in this case is close to zero coordinate.
+
+ * \param ar The region (used for the window width and height).
+ * \param mval The area relative 2d location (such as event->mval converted to floats).
+ * \param out The resulting normalized world-space direction vector.
+ */
+void ED_view3d_win_to_origin(const ARegion *ar, const float mval[2], float out[3])
+{
+	RegionView3D *rv3d = ar->regiondata;
+	if (rv3d->is_persp) {
+		copy_v3_v3(out, rv3d->viewinv[3]);
+	}
+	else {
+		out[0] = 2.0f * mval[0] / ar->winx - 1.0f;
+		out[1] = 2.0f * mval[1] / ar->winy - 1.0f;
+
+		if (rv3d->persp == RV3D_CAMOB) {
+			out[2] = -1.0f;
+		}
+		else {
+			out[2] = 0.0f;
+		}
+
+		mul_project_m4_v3(rv3d->persinv, out);
+	}
+}
+
+/**
  * Calculate a 3d direction vector from 2d window coordinates.
  * This direction vector starts and the view in the direction of the 2d window coordinates.
  * In orthographic view all window coordinates yield the same vector.
@@ -599,7 +614,7 @@ bool ED_view3d_win_to_segment(const ARegion *ar, View3D *v3d, const float mval[2
 
 	/* bounds clipping */
 	if (do_clip) {
-		return view3d_clip_segment((RegionView3D *)ar->regiondata, r_ray_start, r_ray_end);
+		return ED_view3d_clip_segment((RegionView3D *)ar->regiondata, r_ray_start, r_ray_end);
 	}
 
 	return true;