fix [#36349] Separate mesh by material creates meshes with all the materials from the original

4 files changed, 116 insertions, 9 deletions

diff --git a/source/blender/blenkernel/BKE_material.h b/source/blender/blenkernel/BKE_material.h
index f52dc030873..91c1715cca6 100644
--- a/source/blender/blenkernel/BKE_material.h
+++ b/source/blender/blenkernel/BKE_material.h
@@ -50,7 +50,7 @@ void init_def_material(void);
 void BKE_material_free(struct Material *sc); 
 void BKE_material_free_ex(struct Material *ma, int do_id_user);
 void test_object_materials(struct Main *bmain, struct ID *id);
-void resize_object_material(struct Object *ob, const short totcol);
+void BKE_material_resize_object(struct Object *ob, const short totcol, bool do_id_user);
 void init_material(struct Material *ma);
 struct Material *BKE_material_add(struct Main *bmain, const char *name);
 struct Material *BKE_material_copy(struct Material *ma);
@@ -87,6 +87,7 @@ int object_add_material_slot(struct Object *ob);
 int object_remove_material_slot(struct Object *ob);
 
 /* rna api */
+void BKE_material_resize_id(struct ID *id, short totcol, bool do_id_user);
 void BKE_material_append_id(struct ID *id, struct Material *ma);
 struct Material *BKE_material_pop_id(struct ID *id, int index, bool update_data); /* index is an int because of RNA */
 void BKE_material_clear_id(struct ID *id, bool update_data);
diff --git a/source/blender/blenkernel/intern/material.c b/source/blender/blenkernel/intern/material.c
index 1bda662a8b0..c23b4ac4408 100644
--- a/source/blender/blenkernel/intern/material.c
+++ b/source/blender/blenkernel/intern/material.c
@@ -573,6 +573,34 @@ static void material_data_index_clear_id(ID *id)
 	}
 }
 
+void BKE_material_resize_id(struct ID *id, short totcol, bool do_id_user)
+{
+	Material ***matar = give_matarar_id(id);
+	short *totcolp = give_totcolp_id(id);
+
+	if (matar == NULL) {
+		return;
+	}
+
+	if (do_id_user && totcol < (*totcolp)) {
+		short i;
+		for (i = totcol; i < (*totcolp); i++) {
+			id_us_min((ID *)(*matar)[i]);
+		}
+	}
+
+	if (totcol == 0) {
+		if (*totcolp) {
+			MEM_freeN(*matar);
+			*matar = NULL;
+		}
+	}
+	else {
+		*matar = MEM_recallocN(*matar, sizeof(void *) * totcol);
+	}
+	*totcolp = totcol;
+}
+
 void BKE_material_append_id(ID *id, Material *ma)
 {
 	Material ***matar;
@@ -708,11 +736,18 @@ Material *give_node_material(Material *ma)
 	return NULL;
 }
 
-void resize_object_material(Object *ob, const short totcol)
+void BKE_material_resize_object(Object *ob, const short totcol, bool do_id_user)
 {
 	Material **newmatar;
 	char *newmatbits;
 
+	if (do_id_user && totcol < ob->totcol) {
+		short i;
+		for (i = totcol; i < ob->totcol; i++) {
+			id_us_min((ID *)ob->mat[i]);
+		}
+	}
+
 	if (totcol == 0) {
 		if (ob->totcol) {
 			MEM_freeN(ob->mat);
@@ -733,6 +768,8 @@ void resize_object_material(Object *ob, const short totcol)
 		ob->mat = newmatar;
 		ob->matbits = newmatbits;
 	}
+	/* XXX, why not realloc on shrink? - campbell */
+
 	ob->totcol = totcol;
 	if (ob->totcol && ob->actcol == 0) ob->actcol = 1;
 	if (ob->actcol > ob->totcol) ob->actcol = ob->totcol;
@@ -750,7 +787,7 @@ void test_object_materials(Main *bmain, ID *id)
 
 	for (ob = bmain->object.first; ob; ob = ob->id.next) {
 		if (ob->data == id) {
-			resize_object_material(ob, *totcol);
+			BKE_material_resize_object(ob, *totcol, false);
 		}
 	}
 }
diff --git a/source/blender/blenloader/intern/readfile.c b/source/blender/blenloader/intern/readfile.c
index 1f8bbfbec88..22ab7e49973 100644
--- a/source/blender/blenloader/intern/readfile.c
+++ b/source/blender/blenloader/intern/readfile.c
@@ -4345,7 +4345,7 @@ static void lib_link_object(FileData *fd, Main *main)
 				/* Only expand so as not to loose any object materials that might be set. */
 				if (totcol_data && (*totcol_data > ob->totcol)) {
 					/* printf("'%s' %d -> %d\n", ob->id.name, ob->totcol, *totcol_data); */
-					resize_object_material(ob, *totcol_data);
+					BKE_material_resize_object(ob, *totcol_data, false);
 				}
 			}
 			
diff --git a/source/blender/editors/mesh/editmesh_tools.c b/source/blender/editors/mesh/editmesh_tools.c
index 4610bb89ae4..38ce56b4bc7 100644
--- a/source/blender/editors/mesh/editmesh_tools.c
+++ b/source/blender/editors/mesh/editmesh_tools.c
@@ -2399,7 +2399,7 @@ void MESH_OT_knife_cut(wmOperatorType *ot)
 	RNA_def_int(ot->srna, "cursor", BC_KNIFECURSOR, 0, INT_MAX, "Cursor", "", 0, INT_MAX);
 }
 
-static int mesh_separate_tagged(Main *bmain, Scene *scene, Base *base_old, BMesh *bm_old)
+static Base *mesh_separate_tagged(Main *bmain, Scene *scene, Base *base_old, BMesh *bm_old)
 {
 	Base *base_new;
 	Object *obedit = base_old->object;
@@ -2441,7 +2441,7 @@ static int mesh_separate_tagged(Main *bmain, Scene *scene, Base *base_old, BMesh
 	BM_mesh_free(bm_new);
 	((Mesh *)base_new->object->data)->edit_btmesh = NULL;
 	
-	return true;
+	return base_new;
 }
 
 static bool mesh_separate_selected(Main *bmain, Scene *scene, Base *base_old, BMesh *bm_old)
@@ -2452,7 +2452,7 @@ static bool mesh_separate_selected(Main *bmain, Scene *scene, Base *base_old, BM
 	/* sel -> tag */
 	BM_mesh_elem_hflag_enable_test(bm_old, BM_FACE | BM_EDGE | BM_VERT, BM_ELEM_TAG, true, BM_ELEM_SELECT);
 
-	return mesh_separate_tagged(bmain, scene, base_old, bm_old);
+	return (mesh_separate_tagged(bmain, scene, base_old, bm_old) != NULL);
 }
 
 /* flush a hflag to from verts to edges/faces */
@@ -2492,6 +2492,63 @@ static void bm_mesh_hflag_flush_vert(BMesh *bm, const char hflag)
 	}
 }
 
+/**
+ * Sets an object to a single material. from one of its slots.
+ *
+ * \note This could be used for split-by-material for non mesh types.
+ * \note This could take material data from another object or args.
+ */
+static void mesh_separate_material_assign_mat_nr(Object *ob, const short mat_nr)
+{
+	ID *obdata = ob->data;
+
+	Material ***matarar;
+	short *totcolp;
+
+	totcolp = give_totcolp_id(obdata);
+	matarar = give_matarar_id(obdata);
+
+	if ((totcolp && matarar) == 0) {
+		BLI_assert(0);
+		return;
+	}
+
+	if (*totcolp) {
+		Material *ma_ob;
+		Material *ma_obdata;
+		char matbit;
+
+		if (mat_nr < ob->totcol) {
+			ma_ob = ob->mat[mat_nr];
+			matbit = ob->matbits[mat_nr];
+		}
+		else {
+			ma_ob = NULL;
+			matbit = 0;
+		}
+
+		if (mat_nr < *totcolp) {
+			 ma_obdata = (*matarar)[mat_nr];
+		}
+		else {
+			ma_obdata = NULL;
+		}
+
+		BKE_material_clear_id(obdata, true);
+		BKE_material_resize_object(ob, 1, true);
+		BKE_material_resize_id(obdata, 1, true);
+
+		ob->mat[0] = ma_ob;
+		ob->matbits[0] = matbit;
+		(*matarar)[0] = ma_obdata;
+	}
+	else {
+		BKE_material_clear_id(obdata, true);
+		BKE_material_resize_object(ob, 0, true);
+		BKE_material_resize_id(obdata, 0, true);
+	}
+}
+
 static bool mesh_separate_material(Main *bmain, Scene *scene, Base *base_old, BMesh *bm_old)
 {
 	BMFace *f_cmp, *f;
@@ -2499,6 +2556,7 @@ static bool mesh_separate_material(Main *bmain, Scene *scene, Base *base_old, BM
 	bool result = false;
 
 	while ((f_cmp = BM_iter_at_index(bm_old, BM_FACES_OF_MESH, NULL, 0))) {
+		Base *base_new;
 		const short mat_nr = f_cmp->mat_nr;
 		int tot = 0;
 
@@ -2522,11 +2580,22 @@ static bool mesh_separate_material(Main *bmain, Scene *scene, Base *base_old, BM
 
 		/* leave the current object with some materials */
 		if (tot == bm_old->totface) {
+			mesh_separate_material_assign_mat_nr(base_old->object, mat_nr);
+
+			/* since we're in editmode, must set faces here */
+			BM_ITER_MESH (f, &iter, bm_old, BM_FACES_OF_MESH) {
+				f->mat_nr = 0;
+			}
 			break;
 		}
 
 		/* Move selection into a separate object */
-		result |= mesh_separate_tagged(bmain, scene, base_old, bm_old);
+		base_new = mesh_separate_tagged(bmain, scene, base_old, bm_old);
+		if (base_new) {
+			mesh_separate_material_assign_mat_nr(base_new->object, mat_nr);
+		}
+
+		result |= (base_new != NULL);
 	}
 
 	return result;
@@ -2585,7 +2654,7 @@ static bool mesh_separate_loose(Main *bmain, Scene *scene, Base *base_old, BMesh
 		bm_mesh_hflag_flush_vert(bm_old, BM_ELEM_TAG);
 
 		/* Move selection into a separate object */
-		result |= mesh_separate_tagged(bmain, scene, base_old, bm_old);
+		result |= (mesh_separate_tagged(bmain, scene, base_old, bm_old) != NULL);
 	}
 
 	return result;