fix and test #2335

tests/test_obj.py

@@ -28,6 +28,18 @@ def test_no_img(self):
         rec = g.roundtrip(m.export(file_type="obj"), file_type="obj")
         assert g.np.isclose(m.area, rec.area)
 
+    def test_keep_unreferenced(self):
+        # try loading a short mesh with 2 vertices, one of which is referenced
+        m = g.trimesh.load(
+            g.trimesh.util.wrap_as_stream("o mesh\nv 1 1 1\nv 1 1 2\nf 1 1 1"),
+            file_type="obj",
+            process=False,
+            maintain_order=True,
+        )
+
+        assert g.np.allclose(m.faces[0], [0, 0, 0])
+        assert g.np.allclose(m.vertices, [[1, 1, 1], [1, 1, 2]])
+
     def test_trailing(self):
         # test files with texture and trailing slashes
         m = g.get_mesh("jacked.obj")
@@ -335,6 +347,9 @@ def test_mtl_color_roundtrip(self):
 
     def test_scene_export_material_name(self):
         s = g.get_mesh("fuze.obj", force="scene")
+
+        g.log.warning(s.geometry)
+
         dummy = "fuxx"
         s.geometry["fuze.obj"].visual.material.name = dummy
 

trimesh/exchange/load.py

@@ -78,8 +78,10 @@ def load(
     **kwargs,
 ) -> Geometry:
     """
-    Load a mesh or vectorized path into objects like
-    Trimesh, Path2D, Path3D, Scene
+
+    For new code the typed load functions `trimesh.load_scene` or `trimesh.load_mesh`
+    are recommended over `trimesh.load` which is a backwards-compatibility wrapper
+    that mimics the behavior of the old function and can return any geometry type.
 
     Parameters
     -----------
@@ -103,6 +105,7 @@ def load(
       Loaded geometry as trimesh classes
     """
 
+    # call the most general loading case into a `Scene`.
     loaded = load_scene(
         file_obj=file_obj,
         file_type=file_type,
@@ -111,12 +114,25 @@ def load(
         **kwargs,
     )
 
-    # combine a scene into a single mesh
     if force == "mesh":
+        # new code should use `load_mesh` for this
         log.debug(
-            "`trimesh.load_mesh` does the same thing as `trimesh.load(force='mesh')`"
+            "`trimesh.load(force='mesh')` is a compatibility wrapper for `trimesh.load_mesh`"
         )
         return loaded.to_mesh()
+    elif force == "scene":
+        # new code should use `load_scene` for this
+        log.debug(
+            "`trimesh.load(force='scene')` is a compatibility wrapper for `trimesh.load_scene`"
+        )
+        return loaded
+
+    # else:
+    #    log.debug(
+    #        "For new code the typed load functions `trimesh.load_scene` or `trimesh.load_mesh` "
+    #        + "are recommended over `trimesh.load` which is a backwards-compatibility wrapper "
+    #        + "that mimics the behavior of the old function and can return any geometry type."
+    #    )
 
     ###########################################
     # we are matching deprecated behavior here!
@@ -232,8 +248,8 @@ def load_scene(
         loaded = Scene(loaded)
 
     # add the "file_path" information to the overall scene metadata
-    # if 'metadata' not in kwargs:
-    #    loaded.metadata.update(arg.metadata)
+    if "metadata" not in kwargs:
+        loaded.metadata.update(arg.metadata)
     # add the load path metadata to every geometry
     # [g.metadata.update(arg.metadata) for g in loaded.geometry.values()]
 

trimesh/exchange/obj.py

@@ -163,10 +163,12 @@ def load_obj(
             log.debug("faces have mixed data: using slow fallback!")
             faces, faces_tex, faces_norm = _parse_faces_fallback(face_lines)
 
-        if group_material:
+        if group_material and len(materials) > 1:
             name = material
-        else:
+        elif current_object is not None:
             name = current_object
+        else:
+            name = kwargs.get("metadata", {}).get("file_name", "geometry")
 
         # ensure the name is always unique
         name = util.unique_name(name, geometry)
@@ -218,9 +220,13 @@ def load_obj(
                     faces, faces_norm, maintain_faces=maintain_order
                 )
             else:
+                # face_tex is None and
                 # generate the mask so we only include
                 # referenced vertices in every new mesh
-                mask_v = np.zeros(len(v), dtype=bool)
+                if maintain_order:
+                    mask_v = np.ones(len(v), dtype=bool)
+                else:
+                    mask_v = np.zeros(len(v), dtype=bool)
                 mask_v[faces] = True
 
                 # reconstruct the faces with the new vertex indices
@@ -269,17 +275,11 @@ def load_obj(
         # store geometry by name
         geometry[name] = mesh
 
-    if len(geometry) == 1:
-        # TODO : should this be removed to always return a scene?
-        return next(iter(geometry.values()))
-
     # add an identity transform for every geometry
     graph = [{"geometry": k, "frame_to": k} for k in geometry.keys()]
 
     # convert to scene kwargs
-    result = {"geometry": geometry, "graph": graph}
-
-    return result
+    return {"geometry": geometry, "graph": graph}
 
 
 def parse_mtl(mtl, resolver=None):