3D export fixes and tests (#4368)

* WIP 3D export fixes and tests

* print

* errant copypasta

* move rewrite asset logic to scene_3d

* cleanup 3d import/export tests a bit

fiftyone/core/threed/scene_3d.py

@@ -248,13 +248,57 @@ def traverse(self, include_self=False):
 
         Args:
             include_self: whether to include the current node in the traversal
+
+        Yields:
+            :class:`Object3D`
+
         """
         if include_self:
             yield self
 
         for child in self.children:
             yield from child.traverse(include_self=True)
 
+    def update_asset_paths(self, asset_rewrite_paths: dict):
+        """Update asset paths in this scene according to an input dict mapping.
+
+        Asset path is unchanged if it does not exist in ``asset_rewrite_paths``
+
+        Args:
+            asset_rewrite_paths: ``dict`` mapping asset path to new asset path
+
+        Returns:
+            ``True`` if the scene was modified.
+        """
+        scene_modified = False
+        for node in self.traverse():
+            for path_attribute in node._asset_path_fields:
+                asset_path = getattr(node, path_attribute, None)
+                new_asset_path = asset_rewrite_paths.get(asset_path)
+
+                if asset_path is not None and asset_path != new_asset_path:
+                    setattr(node, path_attribute, new_asset_path)
+                    scene_modified = True
+
+        # modify scene background paths, if any
+        if self.background is not None:
+            if self.background.image is not None:
+                new_asset_path = asset_rewrite_paths.get(self.background.image)
+                if new_asset_path != self.background.image:
+                    self.background.image = new_asset_path
+                    scene_modified = True
+
+            if self.background.cube is not None:
+                new_cube = [
+                    asset_rewrite_paths.get(face)
+                    for face in self.background.cube
+                ]
+                if new_cube != self.background.cube:
+                    self.background.cube = new_cube
+                    scene_modified = True
+
+        return scene_modified
+
     def get_scene_summary(self):
         """Returns a summary of the scene."""
         node_types = Counter(map(type, self.traverse()))

fiftyone/utils/data/exporters.py

@@ -1171,6 +1171,7 @@ def _handle_fo3d_file(self, fo3d_path, fo3d_output_path, export_mode):
         scene = fo3d.Scene.from_fo3d(fo3d_path)
         asset_paths = scene.get_asset_paths()
 
+        input_to_output_paths = {}
         for asset_path in asset_paths:
             if not os.path.isabs(asset_path):
                 absolute_asset_path = os.path.join(
@@ -1181,12 +1182,15 @@ def _handle_fo3d_file(self, fo3d_path, fo3d_output_path, export_mode):
 
             seen = self._filename_maker.seen_input_path(absolute_asset_path)
 
-            if seen:
-                continue
-
             asset_output_path = self._filename_maker.get_output_path(
                 absolute_asset_path
             )
+            input_to_output_paths[asset_path] = os.path.relpath(
+                asset_output_path, os.path.dirname(fo3d_output_path)
+            )
+
+            if seen:
+                continue
 
             if export_mode is True:
                 etau.copy_file(absolute_asset_path, asset_output_path)
@@ -1195,41 +1199,7 @@ def _handle_fo3d_file(self, fo3d_path, fo3d_output_path, export_mode):
             elif export_mode == "symlink":
                 etau.symlink_file(absolute_asset_path, asset_output_path)
 
-        is_scene_modified = False
-
-        for node in scene.traverse():
-            path_attribute = next(
-                (
-                    attr
-                    for attr in fo3d.fo3d_path_attributes
-                    if hasattr(node, attr)
-                ),
-                None,
-            )
-
-            if path_attribute is not None:
-                asset_path = getattr(node, path_attribute)
-
-                is_nested_path = os.path.split(asset_path)[0] != ""
-
-                if asset_path is not None and is_nested_path:
-                    setattr(node, path_attribute, os.path.basename(asset_path))
-                    is_scene_modified = True
-
-        # modify scene background paths, if any
-        if scene.background is not None:
-            if scene.background.image is not None:
-                scene.background.image = os.path.basename(
-                    scene.background.image
-                )
-                is_scene_modified = True
-
-            if scene.background.cube is not None:
-                scene.background.cube = [
-                    os.path.basename(face_path)
-                    for face_path in scene.background.cube
-                ]
-                is_scene_modified = True
+        is_scene_modified = scene.update_asset_paths(input_to_output_paths)
 
         if is_scene_modified:
             # note: we can't have different behavior for "symlink" because