fix bugs when ply doesn't exist

nerfstudio/process_data/metashape_utils.py

@@ -200,6 +200,7 @@ def metashape_to_json(
     summary = []
 
     if ply_filename is not None:
+        assert ply_filename.exists()
         pc = o3d.io.read_point_cloud(str(ply_filename))
         points3D = np.asarray(pc.points)
         points3D = np.einsum("ij,bj->bi", applied_transform[:3, :3], points3D) + applied_transform[:3, 3]

nerfstudio/scripts/process_data.py

@@ -253,15 +253,15 @@ def main(self) -> None:
 
         if self.xml.suffix != ".xml":
             raise ValueError(f"XML file {self.xml} must have a .xml extension")
-        if not self.xml.exists:
+        if not self.xml.exists():
             raise ValueError(f"XML file {self.xml} doesn't exist")
         if self.eval_data is not None:
             raise ValueError("Cannot use eval_data since cameras were already aligned with Metashape.")
 
         if self.ply is not None:
             if self.ply.suffix != ".ply":
                 raise ValueError(f"PLY file {self.ply} must have a .ply extension")
-            if not self.ply.exists:
+            if not self.ply.exists():
                 raise ValueError(f"PLY file {self.ply} doesn't exist")
 
         self.output_dir.mkdir(parents=True, exist_ok=True)