feat(splatfacto): record antialiased mode as SplatRenderMode PLY comment

On Gaussian Splat export, write a 'SplatRenderMode: mip|default' PLY
header comment derived from the model's rasterize_mode so viewers can
select a matching rasterization mode. 'mip' is the antialiased mode;
'default' is classic.

- ExportGaussianSplat.write_ply gains an optional 'antialiased' arg
  (None keeps the previous no-comment behavior); export main() passes
  model.config.rasterize_mode == 'antialiased'
- splatfacto exposes rasterize_mode as a disabled/frozen viewer dropdown
  (the viewer renders the live model, so the mode is read from config)
- add a test asserting the comment is written for mip/default/none

nerfstudio/models/splatfacto.py

@@ -294,6 +294,26 @@ class SplatfactoModel(Model):
             raise ValueError(f"""Splatfacto does not support strategy {self.config.strategy}
                              Currently, the supported strategies include default and mcmc.""")
 
+        # Surface the rasterization mode (classic vs antialiased) in the viewer.
+        # The value is baked into the trained model via `rasterize_mode`, so the
+        # control is disabled/frozen: it reflects how the model was trained (and
+        # what a PLY exported from it records as its `SplatRenderMode` comment)
+        # rather than being an interactive toggle. Imported locally to keep the
+        # viewer dependency out of headless import paths.
+        from nerfstudio.viewer.viewer_elements import ViewerDropdown
+
+        self.rasterize_mode_viewer = ViewerDropdown(
+            name="Anti-Aliasing",
+            default_value="antialiased" if self.config.rasterize_mode == "antialiased" else "classic",
+            options=["classic", "antialiased"],
+            disabled=True,
+            hint=(
+                "Rasterization mode this model was trained with (frozen). "
+                "'antialiased' corresponds to a 'SplatRenderMode: mip' comment "
+                "in exported PLY files; 'classic' to 'SplatRenderMode: default'."
+            ),
+        )
+
     @property
     def colors(self):
         if self.config.sh_degree > 0:

nerfstudio/scripts/exporter.py

@@ -503,6 +503,7 @@ class ExportGaussianSplat(Exporter):
         filename: str,
         count: int,
         map_to_tensors: typing.OrderedDict[str, np.ndarray],
+        antialiased: typing.Optional[bool] = None,
     ):
         """
         Writes a PLY file with given vertex properties and a tensor of float or uint8 values in the order specified by the OrderedDict.
@@ -513,6 +514,11 @@ class ExportGaussianSplat(Exporter):
         count (int): The number of vertices to write.
         map_to_tensors (OrderedDict[str, np.ndarray]): An ordered dictionary mapping property names to numpy arrays of float or uint8 values.
             Each array should be 1-dimensional and of equal length matching 'count'. Arrays should not be empty.
+        antialiased (Optional[bool]): Whether the model was trained with the
+            antialiased (mip-splatting) rasterize mode. When not None, a
+            'SplatRenderMode' header comment is written ('mip' when antialiased,
+            'default' otherwise) so viewers can select a matching rasterization
+            mode. When None (default), no such comment is written.
         """
 
         # Ensure count matches the length of all tensors
@@ -535,6 +541,11 @@ class ExportGaussianSplat(Exporter):
             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")
+            # Record the rasterization mode so viewers can match it. 'mip' is the
+            # antialiased mode; 'default' is classic. See SplatfactoModelConfig.
+            if antialiased is not None:
+                render_mode = "mip" if antialiased else "default"
+                ply_file.write(f"comment SplatRenderMode: {render_mode}\n".encode())
             ply_file.write(f"element vertex {count}\n".encode())
 
             # Write properties, in order due to OrderedDict
@@ -646,7 +657,10 @@ class ExportGaussianSplat(Exporter):
                 map_to_tensors[k] = map_to_tensors[k][select]
             count = np.sum(select)
 
-        ExportGaussianSplat.write_ply(str(filename), count, map_to_tensors)
+        # Record whether the model uses the antialiased (mip-splatting) rasterize
+        # mode so the exported PLY carries a matching SplatRenderMode comment.
+        antialiased = model.config.rasterize_mode == "antialiased"
+        ExportGaussianSplat.write_ply(str(filename), count, map_to_tensors, antialiased=antialiased)
 
 
 Commands = tyro.conf.FlagConversionOff[

tests/scripts/test_exporter.py

@@ -76,6 +76,45 @@ def test_export_gaussian_splat_write_ply_mismatched_count(tmp_path: Path):
         ExportGaussianSplat.write_ply(filename, count, map_to_tensors)
 
 
+def _read_ply_header(filename: str) -> str:
+    """Return the ASCII PLY header (up to and including the end_header line)."""
+    with open(filename, "rb") as f:
+        data = f.read()
+    end = data.index(b"end_header")
+    return data[:end].decode("ascii")
+
+
+def _make_valid_tensors(count: int = 10) -> "OrderedDict[str, np.ndarray]":
+    return OrderedDict(
+        [
+            ("x", np.random.rand(count).astype(np.float32)),
+            ("y", np.random.rand(count).astype(np.float32)),
+            ("z", np.random.rand(count).astype(np.float32)),
+        ]
+    )
+
+
+def test_export_gaussian_splat_write_ply_render_mode_comment(tmp_path: Path):
+    count = 10
+
+    # antialiased=True -> mip
+    mip_file = str(tmp_path / "mip.ply")
+    ExportGaussianSplat.write_ply(mip_file, count, _make_valid_tensors(count), antialiased=True)
+    assert "comment SplatRenderMode: mip" in _read_ply_header(mip_file)
+
+    # antialiased=False -> default
+    default_file = str(tmp_path / "default.ply")
+    ExportGaussianSplat.write_ply(default_file, count, _make_valid_tensors(count), antialiased=False)
+    header = _read_ply_header(default_file)
+    assert "comment SplatRenderMode: default" in header
+    assert "comment SplatRenderMode: mip" not in header
+
+    # antialiased=None (default) -> no SplatRenderMode comment (backwards compatible)
+    none_file = str(tmp_path / "none.ply")
+    ExportGaussianSplat.write_ply(none_file, count, _make_valid_tensors(count))
+    assert "SplatRenderMode" not in _read_ply_header(none_file)
+
+
 if __name__ == "__main__":
     # Run the test
     test_export_gaussian_splat_write_ply(Path("."))