fix [#35555] Collada: export destroys mesh in some cases

add arguments to calculate normals when converting to bmesh:
  BM_mesh_bm_from_me, DM_to_bmesh

This gives some speedup to undo (which didnt need to re-calculate vertex normals), and array modifier which doesnt need to calculate face normals at all

5 files changed, 11 insertions, 6 deletions

diff --git a/source/blender/modifiers/intern/MOD_array.c b/source/blender/modifiers/intern/MOD_array.c
index 36461851162..e09fa18ffc5 100644
--- a/source/blender/modifiers/intern/MOD_array.c
+++ b/source/blender/modifiers/intern/MOD_array.c
@@ -228,7 +228,7 @@ static void bm_merge_dm_transform(BMesh *bm, DerivedMesh *dm, float mat[4][4],
 	/* Add the DerivedMesh's elements to the BMesh. The pre-existing
 	 * elements were already tagged, so the new elements can be
 	 * identified by not having the BM_ELEM_TAG flag set. */
-	DM_to_bmesh_ex(dm, bm);
+	DM_to_bmesh_ex(dm, bm, false);
 
 	if (amd->flags & MOD_ARR_MERGE) {
 		/* if merging is enabled, find doubles */
@@ -330,7 +330,7 @@ static DerivedMesh *arrayModifier_doArray(ArrayModifierData *amd,
                                           int UNUSED(initFlags))
 {
 	DerivedMesh *result;
-	BMesh *bm = DM_to_bmesh(dm);
+	BMesh *bm = DM_to_bmesh(dm, false);
 	BMOperator first_dupe_op, dupe_op, old_dupe_op, weld_op;
 	BMVert **first_geom = NULL;
 	int i, j;
diff --git a/source/blender/modifiers/intern/MOD_bevel.c b/source/blender/modifiers/intern/MOD_bevel.c
index cbb0e05aa4a..3713cb817f5 100644
--- a/source/blender/modifiers/intern/MOD_bevel.c
+++ b/source/blender/modifiers/intern/MOD_bevel.c
@@ -113,7 +113,7 @@ static DerivedMesh *applyModifier(ModifierData *md, struct Object *ob,
 	const bool vertex_only = (bmd->flags & BME_BEVEL_VERT) != 0;
 	const bool do_clamp = !(bmd->flags & BME_BEVEL_OVERLAP_OK);
 
-	bm = DM_to_bmesh(dm);
+	bm = DM_to_bmesh(dm, true);
 
 	if (vertex_only) {
 		if ((bmd->lim_flags & BME_BEVEL_VGROUP) && bmd->defgrp_name[0]) {
diff --git a/source/blender/modifiers/intern/MOD_decimate.c b/source/blender/modifiers/intern/MOD_decimate.c
index b8dccd9ffbe..aacf622c185 100644
--- a/source/blender/modifiers/intern/MOD_decimate.c
+++ b/source/blender/modifiers/intern/MOD_decimate.c
@@ -97,6 +97,7 @@ static DerivedMesh *applyModifier(ModifierData *md, Object *ob,
 	DecimateModifierData *dmd = (DecimateModifierData *) md;
 	DerivedMesh *dm = derivedData, *result = NULL;
 	BMesh *bm;
+	bool calc_face_normal;
 
 	float *vweights = NULL;
 
@@ -112,16 +113,19 @@ static DerivedMesh *applyModifier(ModifierData *md, Object *ob,
 			if (dmd->percent == 1.0f) {
 				return dm;
 			}
+			calc_face_normal = true;
 			break;
 		case MOD_DECIM_MODE_UNSUBDIV:
 			if (dmd->iter == 0) {
 				return dm;
 			}
+			calc_face_normal = false;
 			break;
 		case MOD_DECIM_MODE_DISSOLVE:
 			if (dmd->angle == 0.0f) {
 				return dm;
 			}
+			calc_face_normal = true;
 			break;
 	}
 
@@ -159,7 +163,7 @@ static DerivedMesh *applyModifier(ModifierData *md, Object *ob,
 		}
 	}
 
-	bm = DM_to_bmesh(dm);
+	bm = DM_to_bmesh(dm, calc_face_normal);
 
 	switch (dmd->mode) {
 		case MOD_DECIM_MODE_COLLAPSE:
diff --git a/source/blender/modifiers/intern/MOD_edgesplit.c b/source/blender/modifiers/intern/MOD_edgesplit.c
index 0c50d4d3323..d877932b81d 100644
--- a/source/blender/modifiers/intern/MOD_edgesplit.c
+++ b/source/blender/modifiers/intern/MOD_edgesplit.c
@@ -56,8 +56,9 @@ static DerivedMesh *doEdgeSplit(DerivedMesh *dm, EdgeSplitModifierData *emd, Obj
 	BMIter iter;
 	BMEdge *e;
 	float threshold = cosf((emd->split_angle + 0.00001f) * (float)M_PI / 180.0f);
+	const bool calc_face_normals = (emd->flags & MOD_EDGESPLIT_FROMANGLE) != 0;
 
-	bm = DM_to_bmesh(dm);
+	bm = DM_to_bmesh(dm, calc_face_normals);
 	
 	if (emd->flags & MOD_EDGESPLIT_FROMANGLE) {
 		BM_ITER_MESH (e, &iter, bm, BM_EDGES_OF_MESH) {
diff --git a/source/blender/modifiers/intern/MOD_triangulate.c b/source/blender/modifiers/intern/MOD_triangulate.c
index fd0bc218bc4..9155aa0044b 100644
--- a/source/blender/modifiers/intern/MOD_triangulate.c
+++ b/source/blender/modifiers/intern/MOD_triangulate.c
@@ -40,7 +40,7 @@ static DerivedMesh *triangulate_dm(DerivedMesh *dm, const int flag)
 	int total_edges, i;
 	MEdge *me;
 
-	bm = DM_to_bmesh(dm);
+	bm = DM_to_bmesh(dm, true);
 
 	BM_mesh_triangulate(bm, (flag & MOD_TRIANGULATE_BEAUTY), false, NULL, NULL);