tag exported ply files (#3472)

* tag exported ply files

* Added the version

* fix import order

* Added information about the up-axis

nerfstudio/scripts/exporter.py

@@ -24,6 +24,7 @@ import sys
 import typing
 from collections import OrderedDict
 from dataclasses import dataclass, field
+from importlib.metadata import version
 from pathlib import Path
 from typing import List, Optional, Tuple, Union, cast
 
@@ -534,10 +535,12 @@ class ExportGaussianSplat(Exporter):
             raise ValueError("All tensors must be numpy arrays of float or uint8 type and not empty")
 
         with open(filename, "wb") as ply_file:
+            nerfstudio_version = version("nerfstudio")
             # Write PLY header
             ply_file.write(b"ply\n")
             ply_file.write(b"format binary_little_endian 1.0\n")
-
+            ply_file.write(f"comment Generated by Nerstudio {nerfstudio_version}\n".encode())
+            ply_file.write(b"comment Vertical Axis: z\n")
             ply_file.write(f"element vertex {count}\n".encode())
 
             # Write properties, in order due to OrderedDict