feat(Blenvy): added basics of correct multi-material meshes support

* relying on the fact that the mesh-per-material generated by the gltf exporter is deterministic:
ie always uses the ordering of materials in an object
 * added new component MaterialInfos (plural) with a vec of MaterialInfo's
 * modified how materials per object are gathered on the Blender side
 * and modified the processing on the Bevy side to also use the ordered approach
 * seems to work well so far !

crates/blenvy/src/blueprints/materials.rs

@@ -10,14 +10,18 @@ pub struct MaterialInfo {
     pub path: String,
 }
 
+#[derive(Component, Reflect, Default, Debug)]
+#[reflect(Component)]
+pub struct MaterialInfos(Vec<MaterialInfo>);
+
 #[derive(Component, Default, Debug)]
 pub struct MaterialProcessed;
 
 /// system that injects / replaces materials from material library
 pub(crate) fn inject_materials(
     mut blenvy_config: ResMut<BlenvyConfig>,
-    material_infos: Query<
-        (Entity, &MaterialInfo, &Children),
+    material_infos_query: Query<
+        (Entity, &MaterialInfos, &Children),
         Without<MaterialProcessed>, // (With<BlueprintReadyForPostProcess>)
                                     /*(
                                         Added<BlueprintMaterialAssetsLoaded>,
@@ -37,7 +41,8 @@ pub(crate) fn inject_materials(
 
     mut commands: Commands,
 ) {
-    for (entity, material_info, children) in material_infos.iter() {
+    for (entity, material_infos, children) in material_infos_query.iter() {
+        for (material_index, material_info) in material_infos.0.iter().enumerate() {
             let material_full_path = format!("{}#{}", material_info.path, material_info.name);
             let mut material_found: Option<&Handle<StandardMaterial>> = None;
     
@@ -74,10 +79,9 @@ pub(crate) fn inject_materials(
                 }
             }
 
-        commands.entity(entity).insert(MaterialProcessed);
-
             if let Some(material) = material_found {
-            for child in children.iter() {
+                for (child_index, child) in children.iter().enumerate() {
+                    if child_index == material_index {
                         if with_materials_and_meshes.contains(*child) {
                             info!(
                                 "injecting material {}, path: {:?}",
@@ -88,6 +92,14 @@ pub(crate) fn inject_materials(
                             commands.entity(*child).insert(material.clone());
                         }
                     }
+                    
                 }
             }
         }
+       
+
+        commands.entity(entity).insert(MaterialProcessed);
+
+        
+    }
+}

crates/blenvy/src/blueprints/mod.rs

@@ -91,6 +91,8 @@ impl Plugin for BlueprintsPlugin {
             .add_event::<BlueprintEvent>()
             .register_type::<BlueprintInfo>()
             .register_type::<MaterialInfo>()
+            .register_type::<MaterialInfos>()
+
             .register_type::<SpawnBlueprint>()
             .register_type::<BlueprintInstanceDisabled>()
             .register_type::<HideUntilReady>()

tools/blenvy/add_ons/auto_export/common/auto_export.py

@@ -102,7 +102,7 @@ def auto_export(changes_per_scene, changes_per_collection, changes_per_material,
             old_selections = bpy.context.selected_objects
 
             # deal with materials
-            if export_materials_library:
+            if export_materials_library and len(materials_to_export) > 0:
                 print("export MATERIALS")
                 export_materials(materials_to_export, settings, blueprints_data)
 

tools/blenvy/add_ons/auto_export/common/export_gltf.py

@@ -73,7 +73,7 @@ def generate_gltf_export_settings(settings):
         if str(key) not in constant_keys:
             gltf_export_settings[key] =  standard_gltf_exporter_settings.get(key)
 
-    print("GLTF EXPORT SETTINGS", gltf_export_settings)
+    #print("GLTF EXPORT SETTINGS", gltf_export_settings)
     return gltf_export_settings
 
 

tools/blenvy/add_ons/auto_export/materials/export_materials.py

@@ -46,6 +46,13 @@ def generate_materials_scene_content(root_collection, used_material_names):
         make_material_object("Material_"+material_name, [index * 0.2,0,0], material=material, collection=root_collection)
     return {}
 
+# generates a scene for a given material
+def generate_material_scene_content(root_collection, material_name):
+    material = bpy.data.materials[material_name]
+    make_material_object(f"Material_{material_name}", [0,0,0], material=material, collection=root_collection)
+    return {}
+
+
 def clear_materials_scene(temp_scene):
     root_collection = temp_scene.collection 
     scene_objects = [o for o in root_collection.objects]
@@ -83,9 +90,23 @@ def export_materials(materials_to_export, settings, blueprints_data):
                         'export_apply':True
                         }
 
+
+
+        for material in materials_to_export:
+            print("exporting material", material.name)
+            gltf_output_path = os.path.join(materials_path_full, material.name)
+
+            generate_temporary_scene_and_export(
+                settings=settings, 
+                gltf_export_settings=gltf_export_settings,
+                temp_scene_name="__materials_scene",
+                gltf_output_path=gltf_output_path,
+                tempScene_filler= lambda temp_collection: generate_material_scene_content(temp_collection, material.name),
+                tempScene_cleaner= lambda temp_scene, params: clear_materials_scene(temp_scene=temp_scene)
+            )
+
         current_project_name = Path(bpy.context.blend_data.filepath).stem
         gltf_output_path = os.path.join(materials_path_full, current_project_name + "_materials")
-
         print("       exporting Materials to", gltf_output_path, ".gltf/glb")
 
         generate_temporary_scene_and_export(

tools/blenvy/add_ons/auto_export/materials/get_materials_to_export.py

@@ -8,12 +8,17 @@ def get_materials_to_export(changes_per_material, changed_export_parameters, blu
     materials_path_full = getattr(settings,"materials_path_full", "")
 
     change_detection = getattr(settings.auto_export, "change_detection")
+    export_materials_library = getattr(settings.auto_export, "export_materials_library")
     collection_instances_combine_mode = getattr(settings.auto_export, "collection_instances_combine_mode")
 
     all_materials = bpy.data.materials
     local_materials = [material for material in all_materials if material.library is None]
     materials_to_export = []
-    if change_detection and not changed_export_parameters:
+
+    if export_materials_library and change_detection:
+        if changed_export_parameters:
+            materials_to_export = [bpy.data.materials[material_name] for material_name in list(changes_per_material.keys())] # TODO: should be based on the list of materials in use
+        else :
             changed_materials = [bpy.data.materials[material_name] for material_name in list(changes_per_material.keys())]
 
             # first check if all materials have already been exported before (if this is the first time the exporter is run
@@ -24,5 +29,5 @@ def get_materials_to_export(changes_per_material, changed_export_parameters, blu
             #materials_always_export = [material for material in internal_materials if is_material_always_export(material)]
             materials_always_export = []
             materials_to_export =  list(set(changed_materials + materials_not_on_disk + materials_always_export))
-
+    print("materials_to_export", materials_to_export, local_materials)
     return materials_to_export

tools/blenvy/materials/materials_helpers.py

@@ -40,7 +40,9 @@ def get_materials(object, materials_per_object):
         # print("    slot", m, "material", material)
         used_materials_names.append(material.name)
         # TODO:, also respect slots & export multiple materials if applicable ! 
-        materials_per_object[object] = material
+        if not object in materials_per_object:
+            materials_per_object[object] = []
+        materials_per_object[object].append(material)
     return used_materials_names
 
 
@@ -68,16 +70,18 @@ def add_material_info_to_objects(materials_per_object, settings):
     materials_exported_path = posixpath.join(materials_path, f"{materials_library_name}{export_gltf_extension}")
     #print("ADDING MAERIAL INFOS")
     for object in materials_per_object.keys():
-        material = materials_per_object[object]
-
+        material_infos = []
+        for material in materials_per_object[object]:
             # problem with using actual components: you NEED the type registry/component infos, so if there is none , or it is not loaded yet, it does not work
             # for a few components we could hardcode this
-        component_value = f'(name: "{material.name}", path: "{materials_exported_path}")' 
+            material_info = f'(name: "{material.name}", path: "{materials_exported_path}")' 
             #bpy.ops.blenvy.component_add(target_item_name=object.name, target_item_type="OBJECT", component_type="blenvy::blueprints::materials::MaterialInfo", component_value=component_value)
 
             materials_exported_path = posixpath.join(materials_path, f"{materials_library_name}{export_gltf_extension}")
-        object['MaterialInfo'] = component_value
-        print("adding materialInfo to object", object, "material info", component_value)
+            #object['MaterialInfo'] = component_value
+            material_infos.append(material_info)
+        object['MaterialInfos'] = f"({material_infos})".replace("'","") 
+        print("adding materialInfos to object", object, "material infos", material_infos)
 
 
 # get all the materials of all objects in a given scene