glTF exporter: vertex group check enhancement + glTF file fixed order

io_scene_gltf2/blender/exp/gltf2_blender_export.py

@@ -39,7 +39,7 @@ def save(context, export_settings):
 def __export(export_settings):
     export_settings['gltf_channelcache'] = dict()
     exporter = GlTF2Exporter(__get_copyright(export_settings))
-    __add_root_objects(exporter, export_settings)
+    __gather_gltf(exporter, export_settings)
     buffer = __create_buffer(exporter, export_settings)
     exporter.finalize_images(export_settings[gltf2_blender_export_keys.FILE_DIRECTORY])
     json = __fix_json(exporter.glTF.to_dict())
@@ -53,7 +53,7 @@ def __get_copyright(export_settings):
     return None
 
 
-def __add_root_objects(exporter, export_settings):
+def __gather_gltf(exporter, export_settings):
     scenes, animations = gltf2_blender_gather.gather_gltf2(export_settings)
     for scene in scenes:
         exporter.add_scene(scene)
@@ -83,6 +83,8 @@ def __fix_json(obj):
         for key, value in obj.items():
             if value is None:
                 continue
+            elif isinstance(value, dict) and len(value) == 0:
+                continue
             elif isinstance(value, list) and len(value) == 0:
                 continue
             fixed[key] = __fix_json(value)

io_scene_gltf2/blender/exp/gltf2_blender_gather_nodes.py

@@ -208,10 +208,21 @@ def __gather_trans_rot_scale(blender_object, export_settings):
 
 def __gather_skin(blender_object, export_settings):
     modifiers = {m.type: m for m in blender_object.modifiers}
+    if "ARMATURE" not in modifiers:
+        return None
 
-    if "ARMATURE" in modifiers:
-        # Skins and meshes must be in the same glTF node, which is different from how blender handles armatures
-        return gltf2_blender_gather_skins.gather_skin(modifiers["ARMATURE"].object, export_settings)
+    # no skin needed when the modifier is linked without having a vertex group
+    vertex_groups = blender_object.vertex_groups
+    if len(vertex_groups) == 0:
+        return None
+
+    # check if any vertices in the mesh are part of a vertex group
+    blender_mesh = blender_object.to_mesh(bpy.context.depsgraph, True)
+    if not any(vertex.groups is not None and len(vertex.groups) > 0 for vertex in blender_mesh.vertices):
+        return None
+
+    # Skins and meshes must be in the same glTF node, which is different from how blender handles armatures
+    return gltf2_blender_gather_skins.gather_skin(modifiers["ARMATURE"].object, export_settings)
 
 
 def __gather_weights(blender_object, export_settings):

io_scene_gltf2/io/exp/gltf2_io_export.py

@@ -26,24 +26,47 @@ import struct
 #
 # Functions
 #
+from collections import OrderedDict
 
 
-def save_gltf(glTF, export_settings, encoder, glb_buffer):
+def save_gltf(gltf, export_settings, encoder, glb_buffer):
     indent = None
-    separators = separators = (',', ':')
+    separators = (',', ':')
 
     if export_settings['gltf_format'] != 'GLB':
         indent = 4
         # The comma is typically followed by a newline, so no trailing whitespace is needed on it.
-        separators = separators = (',', ' : ')
+        separators = (',', ' : ')
 
-    glTF_encoded = json.dumps(glTF, indent=indent, separators=separators, sort_keys=True, cls=encoder, allow_nan=False)
+    sort_order = [
+        "asset",
+        "extensionsUsed",
+        "extensionsRequired",
+        "extensions",
+        "extras",
+        "scene",
+        "scenes",
+        "nodes",
+        "cameras",
+        "animations",
+        "materials",
+        "meshes",
+        "textures",
+        "images",
+        "skins",
+        "accessors",
+        "bufferViews",
+        "samplers",
+        "buffers"
+    ]
+    gltf_ordered = OrderedDict(sorted(gltf.items(), key=lambda item: sort_order.index(item[0])))
+    gltf_encoded = json.dumps(gltf_ordered, indent=indent, separators=separators, cls=encoder, allow_nan=False)
 
     #
 
     if export_settings['gltf_format'] != 'GLB':
         file = open(export_settings['gltf_filepath'], "w", encoding="utf8", newline="\n")
-        file.write(glTF_encoded)
+        file.write(gltf_encoded)
         file.write("\n")
         file.close()
 
@@ -56,18 +79,18 @@ def save_gltf(glTF, export_settings, encoder, glb_buffer):
     else:
         file = open(export_settings['gltf_filepath'], "wb")
 
-        glTF_data = glTF_encoded.encode()
+        gltf_data = gltf_encoded.encode()
         binary = glb_buffer
 
-        length_gtlf = len(glTF_data)
-        spaces_gltf = (4 - (length_gtlf & 3)) & 3
-        length_gtlf += spaces_gltf
+        length_gltf = len(gltf_data)
+        spaces_gltf = (4 - (length_gltf & 3)) & 3
+        length_gltf += spaces_gltf
 
         length_bin = len(binary)
         zeros_bin = (4 - (length_bin & 3)) & 3
         length_bin += zeros_bin
 
-        length = 12 + 8 + length_gtlf
+        length = 12 + 8 + length_gltf
         if length_bin > 0:
             length += 8 + length_bin
 
@@ -77,9 +100,9 @@ def save_gltf(glTF, export_settings, encoder, glb_buffer):
         file.write(struct.pack("I", length))
 
         # Chunk 0 (JSON)
-        file.write(struct.pack("I", length_gtlf))
+        file.write(struct.pack("I", length_gltf))
         file.write('JSON'.encode())
-        file.write(glTF_data)
+        file.write(gltf_data)
         for i in range(0, spaces_gltf):
             file.write(' '.encode())