Make use/computation of lnors consistant.

Issue was, when requesting (building) lnors for a mesh that has
autosmooth disabled, one would expect to simply get vnors as lnors.

Until now, it wasn't the case, which was bad e.g. for normal projections
of loops in recent remap code (projecting along split loop normals
when you would expect projection along vertex normals...).

Also, removed the 'angle' parameter from RNA's `mesh.calc_normals_split`.
This should *always* use mesh settings (both autosmooth and smoothresh),
otherwise once again we'd get inconsistencies in some cases.
Will update fbx and obj addons too.

2 files changed, 46 insertions, 11 deletions

diff --git a/source/blender/bmesh/intern/bmesh_mesh.c b/source/blender/bmesh/intern/bmesh_mesh.c
index b16ea42304a..95d40bfc0c6 100644
--- a/source/blender/bmesh/intern/bmesh_mesh.c
+++ b/source/blender/bmesh/intern/bmesh_mesh.c
@@ -650,6 +650,31 @@ static void bm_mesh_loops_calc_normals(BMesh *bm, const float (*vcos)[3], const
 	}
 }
 
+static void bm_mesh_loops_from_vert_normals(BMesh *bm, const float (*vnos)[3], float (*r_lnos)[3])
+{
+	BMIter fiter;
+	BMFace *f_curr;
+
+	{
+		char htype = BM_LOOP;
+		if (vnos) {
+			htype |= BM_VERT;
+		}
+		BM_mesh_elem_index_ensure(bm, htype);
+	}
+
+	BM_ITER_MESH (f_curr, &fiter, bm, BM_FACES_OF_MESH) {
+		BMLoop *l_curr, *l_first;
+
+		l_curr = l_first = BM_FACE_FIRST_LOOP(f_curr);
+		do {
+			const float *no = vnos ? vnos[BM_elem_index_get(l_curr->v)] : l_curr->v->no;
+			copy_v3_v3(r_lnos[BM_elem_index_get(l_curr)], no);
+
+		} while ((l_curr = l_curr->next) != l_first);
+	}
+}
+
 #if 0  /* Unused currently */
 /**
  * \brief BMesh Compute Loop Normals
@@ -657,13 +682,18 @@ static void bm_mesh_loops_calc_normals(BMesh *bm, const float (*vcos)[3], const
  * Updates the loop normals of a mesh. Assumes vertex and face normals are valid (else call BM_mesh_normals_update()
  * first)!
  */
-void BM_mesh_loop_normals_update(BMesh *bm, const float split_angle, float (*r_lnos)[3])
+void BM_mesh_loop_normals_update(BMesh *bm, const bool use_split_normals, const float split_angle, float (*r_lnos)[3])
 {
-	/* Tag smooth edges and set lnos from vnos when they might be completely smooth... */
-	bm_mesh_edges_sharp_tag(bm, NULL, NULL, split_angle, r_lnos);
+	if (use_split_normals) {
+		/* Tag smooth edges and set lnos from vnos when they might be completely smooth... */
+		bm_mesh_edges_sharp_tag(bm, NULL, NULL, split_angle, r_lnos);
 
-	/* Finish computing lnos by accumulating face normals in each fan of faces defined by sharp edges. */
-	bm_mesh_loops_calc_normals(bm, NULL, NULL, r_lnos);
+		/* Finish computing lnos by accumulating face normals in each fan of faces defined by sharp edges. */
+		bm_mesh_loops_calc_normals(bm, NULL, NULL, r_lnos);
+	}
+	else {
+		bm_mesh_loops_from_vert_normals(bm, NULL, r_lnos);
+	}
 }
 #endif
 
@@ -674,13 +704,18 @@ void BM_mesh_loop_normals_update(BMesh *bm, const float split_angle, float (*r_l
  * Useful to materialize sharp edges (or non-smooth faces) without actually modifying the geometry (splitting edges).
  */
 void BM_loops_calc_normal_vcos(BMesh *bm, const float (*vcos)[3], const float (*vnos)[3], const float (*fnos)[3],
-                                const float split_angle, float (*r_lnos)[3])
+                               const bool use_split_normals, const float split_angle, float (*r_lnos)[3])
 {
-	/* Tag smooth edges and set lnos from vnos when they might be completely smooth... */
-	bm_mesh_edges_sharp_tag(bm, vnos, fnos, split_angle, r_lnos);
+	if (use_split_normals) {
+		/* Tag smooth edges and set lnos from vnos when they might be completely smooth... */
+		bm_mesh_edges_sharp_tag(bm, vnos, fnos, split_angle, r_lnos);
 
-	/* Finish computing lnos by accumulating face normals in each fan of faces defined by sharp edges. */
-	bm_mesh_loops_calc_normals(bm, vcos, fnos, r_lnos);
+		/* Finish computing lnos by accumulating face normals in each fan of faces defined by sharp edges. */
+		bm_mesh_loops_calc_normals(bm, vcos, fnos, r_lnos);
+	}
+	else {
+		bm_mesh_loops_from_vert_normals(bm, vnos, r_lnos);
+	}
 }
 
 static void UNUSED_FUNCTION(bm_mdisps_space_set)(Object *ob, BMesh *bm, int from, int to)
diff --git a/source/blender/bmesh/intern/bmesh_mesh.h b/source/blender/bmesh/intern/bmesh_mesh.h
index 22e50502aee..c2ac2c40534 100644
--- a/source/blender/bmesh/intern/bmesh_mesh.h
+++ b/source/blender/bmesh/intern/bmesh_mesh.h
@@ -40,7 +40,7 @@ void   BM_mesh_clear(BMesh *bm);
 void BM_mesh_normals_update(BMesh *bm);
 void BM_verts_calc_normal_vcos(BMesh *bm, const float (*fnos)[3], const float (*vcos)[3], float (*vnos)[3]);
 void BM_loops_calc_normal_vcos(BMesh *bm, const float (*vcos)[3], const float (*vnos)[3], const float (*pnos)[3],
-                               const float split_angle, float (*r_lnos)[3]);
+                               const bool use_split_normals, const float split_angle, float (*r_lnos)[3]);
 
 void bmesh_edit_begin(BMesh *bm, const BMOpTypeFlag type_flag);
 void bmesh_edit_end(BMesh *bm, const BMOpTypeFlag type_flag);