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

source/blender/blenkernel/BKE_DerivedMesh.h

@@ -474,11 +474,11 @@ int DM_release(DerivedMesh *dm);
 void DM_to_mesh(DerivedMesh *dm, struct Mesh *me, struct Object *ob, CustomDataMask mask);
 
 struct BMEditMesh *DM_to_editbmesh(struct DerivedMesh *dm,
-                                   struct BMEditMesh *existing, int do_tessellate);
+                                   struct BMEditMesh *existing, const bool do_tessellate);
 
 /* conversion to bmesh only */
-void          DM_to_bmesh_ex(struct DerivedMesh *dm, struct BMesh *bm);
-struct BMesh *DM_to_bmesh(struct DerivedMesh *dm);
+void          DM_to_bmesh_ex(struct DerivedMesh *dm, struct BMesh *bm, const bool calc_face_normal);
+struct BMesh *DM_to_bmesh(struct DerivedMesh *dm, const bool calc_face_normal);
 
 
 /** Utility function to convert a DerivedMesh to a shape key block */

source/blender/blenkernel/intern/mesh.c

@@ -539,7 +539,7 @@ BMesh *BKE_mesh_to_bmesh(Mesh *me, Object *ob)
 
 	bm = BM_mesh_create(&bm_mesh_allocsize_default);
 
-	BM_mesh_bm_from_me(bm, me, true, ob->shapenr);
+	BM_mesh_bm_from_me(bm, me, false, true, ob->shapenr);
 
 	return bm;
 }

source/blender/blenkernel/intern/modifiers_bmesh.c

@@ -61,7 +61,7 @@ static BMFace *bm_face_create_from_mpoly(MPoly *mp, MLoop *ml,
  *
  * \note The mesh may already have geometry. see 'is_init'
  */
-void DM_to_bmesh_ex(DerivedMesh *dm, BMesh *bm)
+void DM_to_bmesh_ex(DerivedMesh *dm, BMesh *bm, const bool calc_face_normal)
 {
 	MVert *mv, *mvert;
 	MEdge *me, *medge;
@@ -182,11 +182,13 @@ void DM_to_bmesh_ex(DerivedMesh *dm, BMesh *bm)
 
 		CustomData_to_bmesh_block(&dm->polyData, &bm->pdata, i, &f->head.data, true);
 
-		if (face_normals) {
-			copy_v3_v3(f->no, face_normals[i]);
-		}
-		else {
-			BM_face_normal_update(f);
+		if (calc_face_normal) {
+			if (face_normals) {
+				copy_v3_v3(f->no, face_normals[i]);
+			}
+			else {
+				BM_face_normal_update(f);
+			}
 		}
 
 		if (UNLIKELY(has_orig_hflag & BM_FACE)) {
@@ -202,7 +204,7 @@ void DM_to_bmesh_ex(DerivedMesh *dm, BMesh *bm)
 
 /* converts a cddm to a BMEditMesh.  if existing is non-NULL, the
  * new geometry will be put in there.*/
-BMEditMesh *DM_to_editbmesh(DerivedMesh *dm, BMEditMesh *existing, int do_tessellate)
+BMEditMesh *DM_to_editbmesh(DerivedMesh *dm, BMEditMesh *existing, const bool do_tessellate)
 {
 	BMEditMesh *em = existing;
 	BMesh *bm;
@@ -214,7 +216,7 @@ BMEditMesh *DM_to_editbmesh(DerivedMesh *dm, BMEditMesh *existing, int do_tessel
 		bm = BM_mesh_create(&bm_mesh_allocsize_default);
 	}
 
-	DM_to_bmesh_ex(dm, bm);
+	DM_to_bmesh_ex(dm, bm, do_tessellate);
 
 	if (!em) {
 		em = BKE_editmesh_create(bm, do_tessellate);
@@ -228,13 +230,13 @@ BMEditMesh *DM_to_editbmesh(DerivedMesh *dm, BMEditMesh *existing, int do_tessel
 	return em;
 }
 
-BMesh *DM_to_bmesh(DerivedMesh *dm)
+BMesh *DM_to_bmesh(DerivedMesh *dm, const bool calc_face_normal)
 {
 	BMesh *bm;
 
 	bm = BM_mesh_create(&bm_mesh_allocsize_default);
 
-	DM_to_bmesh_ex(dm, bm);
+	DM_to_bmesh_ex(dm, bm, calc_face_normal);
 
 	return bm;
 }

source/blender/bmesh/intern/bmesh_mesh_conv.c

@@ -185,7 +185,8 @@ static BMFace *bm_face_create_from_mpoly(MPoly *mp, MLoop *ml,
  *
  * \warning This function doesn't calculate face normals.
  */
-void BM_mesh_bm_from_me(BMesh *bm, Mesh *me, bool set_key, int act_key_nr)
+void BM_mesh_bm_from_me(BMesh *bm, Mesh *me,
+                        const bool calc_face_normal, const bool set_key, int act_key_nr)
 {
 	MVert *mvert;
 	MEdge *medge;
@@ -397,6 +398,10 @@ void BM_mesh_bm_from_me(BMesh *bm, Mesh *me, bool set_key, int act_key_nr)
 
 		/* Copy Custom Data */
 		CustomData_to_bmesh_block(&me->pdata, &bm->pdata, i, &f->head.data, true);
+
+		if (calc_face_normal) {
+			BM_face_normal_update(f);
+		}
 	}
 
 	bm->elem_index_dirty &= ~BM_FACE; /* added in order, clear dirty flag */

source/blender/bmesh/intern/bmesh_mesh_conv.h

@@ -38,7 +38,8 @@ void BM_mesh_cd_flag_ensure(BMesh *bm, struct Mesh *mesh, const char cd_flag);
 void BM_mesh_cd_flag_apply(BMesh *bm, const char cd_flag);
 char BM_mesh_cd_flag_from_bmesh(BMesh *bm);
 
-void BM_mesh_bm_from_me(BMesh *bm, struct Mesh *me, bool set_key, int act_key_nr);
+void BM_mesh_bm_from_me(BMesh *bm, struct Mesh *me,
+                        const bool calc_face_normal, const bool set_key, int act_key_nr);
 void BM_mesh_bm_to_me(BMesh *bm, struct Mesh *me, bool do_tessface);
 
 #endif /* __BMESH_MESH_CONV_H__ */

source/blender/bmesh/operators/bmo_mesh_conv.c

@@ -45,7 +45,7 @@ void bmo_mesh_to_bmesh_exec(BMesh *bm, BMOperator *op)
 	Mesh *me     = BMO_slot_ptr_get(op->slots_in,  "mesh");
 	bool set_key = BMO_slot_bool_get(op->slots_in, "use_shapekey");
 
-	BM_mesh_bm_from_me(bm, me, set_key, ob->shapenr);
+	BM_mesh_bm_from_me(bm, me, false, set_key, ob->shapenr);
 
 	if (me->key && ob->shapenr > me->key->totkey) {
 		ob->shapenr = me->key->totkey - 1;

source/blender/collada/collada_utils.cpp

@@ -383,12 +383,13 @@ void bc_match_scale(std::vector<Object *> *objects_done,
 
 }
 
-void bc_triangulate_mesh(Mesh *me) {
+void bc_triangulate_mesh(Mesh *me)
+{
 	bool use_beauty = false;
 	bool tag_only   = false;
 	 
 	BMesh *bm = BM_mesh_create(&bm_mesh_allocsize_default);
-	BM_mesh_bm_from_me(bm, me, FALSE, 0);
+	BM_mesh_bm_from_me(bm, me, true, false, 0);
 	BM_mesh_triangulate(bm, use_beauty, tag_only, NULL, NULL);
 	BM_mesh_bm_to_me(bm, me, FALSE);
 	BM_mesh_free(bm);

source/blender/editors/mesh/editmesh_tools.c

@@ -2598,7 +2598,7 @@ static int edbm_separate_exec(bContext *C, wmOperator *op)
 
 					bm_old = BM_mesh_create(&bm_mesh_allocsize_default);
 
-					BM_mesh_bm_from_me(bm_old, me, false, 0);
+					BM_mesh_bm_from_me(bm_old, me, false, false, 0);
 
 					if      (type == 1) retval_iter = mesh_separate_material(bmain, scene, base_iter, bm_old);
 					else if (type == 2) retval_iter = mesh_separate_loose(bmain, scene, base_iter, bm_old);

source/blender/editors/mesh/editmesh_utils.c

@@ -655,10 +655,7 @@ static void undoMesh_to_editbtMesh(void *umv, void *em_v, void *UNUSED(obdata))
 
 	bm = BM_mesh_create(&allocsize);
 
-	BM_mesh_bm_from_me(bm, &um->me, false, ob->shapenr);
-
-	/* face normals need recalculation since we are not calling through an operator */
-	BM_mesh_normals_update(bm);
+	BM_mesh_bm_from_me(bm, &um->me, true, false, ob->shapenr);
 
 	em_tmp = BKE_editmesh_create(bm, true);
 	*em = *em_tmp;

source/blender/editors/sculpt_paint/sculpt.c

@@ -4570,8 +4570,7 @@ void sculpt_dynamic_topology_enable(bContext *C)
 	/* Create triangles-only BMesh */
 	ss->bm = BM_mesh_create(&bm_mesh_allocsize_default);
 
-	BM_mesh_bm_from_me(ss->bm, me, TRUE, ob->shapenr);
-	BM_mesh_normals_update(ss->bm);
+	BM_mesh_bm_from_me(ss->bm, me, true, true, ob->shapenr);
 	sculpt_dynamic_topology_triangulate(ss->bm);
 	BM_data_layer_add(ss->bm, &ss->bm->vdata, CD_PAINT_MASK);
 	BM_mesh_normals_update(ss->bm);

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;

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]) {

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:

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) {

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);
 

source/blender/python/bmesh/bmesh_py_types.c

@@ -917,7 +917,7 @@ static PyObject *bpy_bmesh_to_mesh(BPy_BMesh *self, PyObject *args)
 }
 
 PyDoc_STRVAR(bpy_bmesh_from_object_doc,
-".. method:: from_object(object, scene, deform=True, render=False, cage=False)\n"
+".. method:: from_object(object, scene, deform=True, render=False, cage=False, face_normals=True)\n"
 "\n"
 "   Initialize this bmesh from existing object datablock (currently only meshes are supported).\n"
 "\n"
@@ -929,6 +929,8 @@ PyDoc_STRVAR(bpy_bmesh_from_object_doc,
 "   :type render: boolean\n"
 "   :arg cage: Get the mesh as a deformed cage.\n"
 "   :type cage: boolean\n"
+"   :arg face_normals: Calculate face normals.\n"
+"   :type face_normals: boolean\n"
 );
 static PyObject *bpy_bmesh_from_object(BPy_BMesh *self, PyObject *args)
 {
@@ -940,12 +942,13 @@ static PyObject *bpy_bmesh_from_object(BPy_BMesh *self, PyObject *args)
 	int use_deform = true;
 	int use_render = false;
 	int use_cage   = false;
+	int use_fnorm  = true;
 	DerivedMesh *dm;
 	const int mask = CD_MASK_BMESH;
 
 	BPY_BM_CHECK_OBJ(self);
 
-	if (!PyArg_ParseTuple(args, "OO|iii:from_object", &py_object, &py_scene, &use_render, &use_cage) ||
+	if (!PyArg_ParseTuple(args, "OO|iiii:from_object", &py_object, &py_scene, &use_render, &use_cage, &use_fnorm) ||
 	    !(ob    = PyC_RNA_AsPointer(py_object, "Object")) ||
 	    !(scene = PyC_RNA_AsPointer(py_scene,  "Scene")))
 	{
@@ -1011,7 +1014,7 @@ static PyObject *bpy_bmesh_from_object(BPy_BMesh *self, PyObject *args)
 
 	bm = self->bm;
 
-	DM_to_bmesh_ex(dm, bm);
+	DM_to_bmesh_ex(dm, bm, use_fnorm);
 
 	dm->release(dm);
 
@@ -1020,7 +1023,7 @@ static PyObject *bpy_bmesh_from_object(BPy_BMesh *self, PyObject *args)
 
 
 PyDoc_STRVAR(bpy_bmesh_from_mesh_doc,
-".. method:: from_mesh(mesh, use_shape_key=False, shape_key_index=0)\n"
+".. method:: from_mesh(mesh, face_normals=True, use_shape_key=False, shape_key_index=0)\n"
 "\n"
 "   Initialize this bmesh from existing mesh datablock.\n"
 "\n"
@@ -1033,15 +1036,16 @@ PyDoc_STRVAR(bpy_bmesh_from_mesh_doc,
 );
 static PyObject *bpy_bmesh_from_mesh(BPy_BMesh *self, PyObject *args, PyObject *kw)
 {
-	static const char *kwlist[] = {"mesh", "use_shape_key", "shape_key_index", NULL};
+	static const char *kwlist[] = {"mesh", "face_normals", "use_shape_key", "shape_key_index", NULL};
 	BMesh *bm;
 	PyObject *py_mesh;
 	Mesh *me;
+	int use_fnorm  = true;
 	int use_shape_key = false;
 	int shape_key_index = 0;
 
-	if (!PyArg_ParseTupleAndKeywords(args, kw, "O|ii:from_mesh", (char **)kwlist,
-	                                 &py_mesh, &use_shape_key, &shape_key_index) ||
+	if (!PyArg_ParseTupleAndKeywords(args, kw, "O|iii:from_mesh", (char **)kwlist,
+	                                 &py_mesh, &use_fnorm, &use_shape_key, &shape_key_index) ||
 	    !(me = PyC_RNA_AsPointer(py_mesh, "Mesh")))
 	{
 		return NULL;
@@ -1049,7 +1053,7 @@ static PyObject *bpy_bmesh_from_mesh(BPy_BMesh *self, PyObject *args, PyObject *
 
 	bm = self->bm;
 
-	BM_mesh_bm_from_me(bm, me, use_shape_key, shape_key_index + 1);
+	BM_mesh_bm_from_me(bm, me, use_fnorm, use_shape_key, shape_key_index + 1);
 
 	Py_RETURN_NONE;
 }