Update how server distinguishes betweeen glTF and blender assets (#53)

Rather than keying on data contained within the .glTF file, server takes
responsibility for all objects added by importing the glTF. Specifically,
put them in a special collection and distinguish nodes based on whether
they are in or out of the collection.

It also cleans up the orientation correction so that the point around
which the imported content gets rotated is explicitly the world origin
(and not any blender-inferred origin).

Author: SeanCurtis-TRI

server.py

@@ -99,6 +99,7 @@ def __init__(
     ):
         self._blend_file = blend_file
         self._bpy_settings_file = bpy_settings_file
+        self._client_objects = None
 
     def reset_scene(self):
         """
@@ -138,15 +139,32 @@ def render_image(self, *, params: RenderParams, output_path: Path):
                 code = compile(f.read(), self._bpy_settings_file, "exec")
                 exec(code, {"bpy": bpy}, dict())
 
+        self._client_objects = bpy.data.collections.new("ClientObjects")
+        old_count = len(bpy.data.objects)
         # Import a glTF file. Note that the Blender glTF importer imposes a
         # +90 degree rotation around the X-axis when loading meshes. Thus, we
         # counterbalance the rotation right after the glTF-loading.
-        # TODO(#39) This is very suspicious. Get to the bottom of it.
         bpy.ops.import_scene.gltf(filepath=str(params.scene))
+        new_count = len(bpy.data.objects)
+        # Reality check that all of the imported objects are selected by
+        # default.
+        assert new_count - old_count == len(bpy.context.selected_objects)
+
+        # TODO(#39) This rotation is very suspicious. Get to the bottom of it.
+        # We explicitly specify the pivot point for the rotation to allow for
+        # glTF files with root nodes with arbitrary positioning. We simply want
+        # to rotate around the world origin.
         bpy.ops.transform.rotate(
-            value=math.pi / 2, orient_axis="X", orient_type="GLOBAL"
+            value=math.pi / 2,
+            orient_axis="X",
+            orient_type="GLOBAL",
+            center_override=(0, 0, 0),
         )
 
+        # All imported objects get put in our "client objects" collection.
+        for obj in bpy.context.selected_objects:
+            self._client_objects.objects.link(obj)
+
         # Set rendering parameters.
         scene = bpy.context.scene
         scene.render.image_settings.file_format = "PNG"
@@ -247,6 +265,13 @@ def label_render_settings(self):
         world_nodes = bpy.data.worlds["World"].node_tree.nodes
         world_nodes["Background"].inputs[0].default_value = background_color
 
+        # Every object imported from the glTF file has been placed in a
+        # special collection; simply test for its presence.
+        assert self._client_objects is not None
+
+        def is_from_gltf(object):
+            return object.name in self._client_objects.objects
+
         # Iterate over all meshes and set their label values.
         for bpy_object in bpy.data.objects:
             assert bpy_object is not None
@@ -257,11 +282,10 @@ def label_render_settings(self):
             if bpy_object.type != "MESH":
                 continue
 
-            # If a mesh is imported from a glTF, its parent node will be
-            # `Renderer Node`, and we will set its label value to its diffuse
-            # color. If a mesh is loaded from a blend file, its label value
-            # will be set to white (same as the background).
-            if bpy_object.parent.name == "Renderer Node":
+            # If a mesh is imported from a glTF, we will set its label value to
+            # its diffuse color. If a mesh is loaded from a blend file, its
+            # label value will be set to white (same as the background).
+            if is_from_gltf(bpy_object):
                 mesh_color = bpy_object.data.materials[0].diffuse_color
             else:
                 mesh_color = background_color

test/one_rgba_box.gltf

@@ -157,7 +157,7 @@
       },
       {
          "children" : [ 0, 1 ],
-         "name" : "Renderer Node"
+         "name" : "Root Node"
       }
    ],
    "scene" : 0,

test/two_rgba_boxes.gltf

@@ -254,7 +254,7 @@
          "name" : "Camera Node"
       },
       {
-         "children" : [ 0, 1, 2 ],
+         "children" : [ 1, 2 ],
          "name" : "Renderer Node"
       }
    ],
@@ -263,7 +263,7 @@
    [
       {
          "name" : "Layer 0",
-         "nodes" : [ 3 ]
+         "nodes" : [ 0, 3 ]
       }
    ]
 }