Add USD to Simularium converter

pyproject.toml

@@ -60,6 +60,9 @@ nerdss = [
 mem3dg = [
   "netCDF4",
 ]
+usd = [
+  "usd-core>=24.0",
+]
 tutorial = [
   "jupyter",
   "scipy>=1.5.2",

simulariumio/tests/converters/test_usd_converter.py

@@ -0,0 +1,217 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+import os
+
+import numpy as np
+import pytest
+
+from simulariumio import DisplayData, JsonWriter
+from simulariumio.constants import DISPLAY_TYPE, VIZ_TYPE
+from simulariumio.usd import UsdConverter, UsdData
+
+# Paths to test USD files
+ASCII_USD = "simulariumio/tests/data/usd/actin_USDascii.usd"
+BINARY_USD = "simulariumio/tests/data/usd/actin_USDbinary.usd"
+
+
+@pytest.fixture
+def ascii_converter():
+    return UsdConverter(
+        UsdData(usd_file_path=ASCII_USD, center=False, trim_to_animation=False)
+    )
+
+
+@pytest.fixture
+def binary_converter():
+    return UsdConverter(
+        UsdData(usd_file_path=BINARY_USD, center=False, trim_to_animation=False)
+    )
+
+
+@pytest.fixture
+def ascii_results(ascii_converter):
+    return JsonWriter.format_trajectory_data(ascii_converter._data)
+
+
+class TestUsdConverterBasic:
+    def test_agent_count(self, ascii_converter):
+        assert ascii_converter._data.agent_data.n_agents[0] == 8
+
+    def test_frame_count(self, ascii_converter):
+        total = len(ascii_converter._data.agent_data.times)
+        assert total == 400
+
+    def test_times(self, ascii_converter):
+        times = ascii_converter._data.agent_data.times
+        assert np.isclose(times[0], 0.0)
+        # Frame 2 at 24fps = 1/24
+        assert np.isclose(times[1], 1.0 / 24.0)
+
+    def test_agent_types(self, ascii_converter):
+        types = ascii_converter._data.agent_data.types[0]
+        expected = [
+            "actin1", "actin2", "actin3", "actin4",
+            "actin5", "actin6", "actin7", "actin8",
+        ]
+        assert types == expected
+
+    def test_viz_types_default(self, ascii_converter):
+        viz = ascii_converter._data.agent_data.viz_types[0]
+        for i in range(8):
+            assert viz[i] == VIZ_TYPE.DEFAULT
+
+
+class TestUsdPositionsAndRotations:
+    def test_first_frame_position(self, ascii_converter):
+        # actin1 at frame 1: translate=(11.259, -0.3637, 5.1427) * metersPerUnit=0.01
+        # then auto-scaled by scale_factor
+        scale = ascii_converter._data.meta_data.scale_factor
+        pos = ascii_converter._data.agent_data.positions[0][0]
+        assert np.isclose(pos[0], 11.259010518398657 * 0.01 * scale, atol=1e-3)
+        assert np.isclose(pos[1], -0.36371288058467566 * 0.01 * scale, atol=1e-3)
+        assert np.isclose(pos[2], 5.142660258715312 * 0.01 * scale, atol=1e-3)
+
+    def test_first_frame_rotation(self, ascii_converter):
+        # actin1 at frame 1: intrinsic XYZ Euler angles matching
+        # THREE.js Euler('XYZ'), stored as radians
+        rot = ascii_converter._data.agent_data.rotations[0][0]
+        assert np.isclose(rot[0], np.radians(177.73), atol=1e-1)
+        assert np.isclose(rot[1], np.radians(30.24), atol=1e-1)
+        assert np.isclose(rot[2], np.radians(-141.48), atol=1e-1)
+
+
+class TestUsdMeshDeduplication:
+    def test_single_obj_for_identical_meshes(self, ascii_converter):
+        assert len(ascii_converter._obj_data) == 1
+
+    def test_all_meshes_map_to_same_obj(self, ascii_converter):
+        obj_files = set(ascii_converter._mesh_to_obj.values())
+        assert len(obj_files) == 1
+        assert "mesh_0.obj" in obj_files
+
+    def test_eight_meshes_tracked(self, ascii_converter):
+        assert len(ascii_converter._mesh_to_obj) == 8
+
+
+class TestUsdMaterialColors:
+    def test_display_data_colors(self, ascii_converter):
+        dd = ascii_converter._data.agent_data.display_data
+        # actin1 color: (0.272, 0.8, 0.272) -> #45cc45
+        assert dd["actin1"].color == "#45cc45"
+        # actin2 color: (0.384, 0.8, 0.123) -> #61cc1f
+        assert dd["actin2"].color == "#61cc1f"
+
+    def test_display_type_obj(self, ascii_converter):
+        dd = ascii_converter._data.agent_data.display_data
+        for name in dd:
+            assert dd[name].display_type == DISPLAY_TYPE.OBJ
+
+    def test_display_url_is_obj_filename(self, ascii_converter):
+        dd = ascii_converter._data.agent_data.display_data
+        for name in dd:
+            assert dd[name].url == "mesh_0.obj"
+
+
+class TestUsdRadii:
+    def test_radius_from_max_distance(self, ascii_converter):
+        # Radius = max distance from any vertex to local origin (with scale
+        # baked in), times metersPerUnit, times scale_factor.
+        # max_dist ≈ 4.3405 for actin mesh (non-uniform scale baked in)
+        scale = ascii_converter._data.meta_data.scale_factor
+        radius = ascii_converter._data.agent_data.radii[0][0]
+        expected = 4.3405 * 0.01 * scale
+        assert np.isclose(radius, expected, atol=1e-2)
+
+
+class TestUsdObjWriting:
+    def test_save_creates_files(self, ascii_converter, tmp_path):
+        output = str(tmp_path / "test_output")
+        ascii_converter.save(output, binary=True)
+
+        assert os.path.exists(output + ".simularium")
+        assert os.path.exists(tmp_path / "mesh_0.obj")
+
+    def test_obj_has_correct_geometry(self, ascii_converter, tmp_path):
+        output = str(tmp_path / "test_output")
+        ascii_converter.save(output, binary=True)
+
+        obj_path = tmp_path / "mesh_0.obj"
+        with open(obj_path) as f:
+            lines = f.readlines()
+
+        v_lines = [l for l in lines if l.startswith("v ")]
+        f_lines = [l for l in lines if l.startswith("f ")]
+        assert len(v_lines) == 4768
+        assert len(f_lines) == 9528
+
+
+class TestUsdTypeMapping:
+    def test_type_mapping_structure(self, ascii_results):
+        tm = ascii_results["trajectoryInfo"]["typeMapping"]
+        # Should have entries for each agent type
+        assert len(tm) == 8
+        # Each should have OBJ display type
+        for tid in tm:
+            assert tm[tid]["geometry"]["displayType"] == "OBJ"
+            assert tm[tid]["geometry"]["url"] == "mesh_0.obj"
+
+
+class TestUsdBinaryFormat:
+    def test_binary_usd_matches_ascii(self, ascii_converter, binary_converter):
+        # Both should produce same number of agents
+        assert (
+            ascii_converter._data.agent_data.n_agents[0]
+            == binary_converter._data.agent_data.n_agents[0]
+        )
+        # Both should produce same mesh dedup
+        assert len(ascii_converter._obj_data) == len(binary_converter._obj_data)
+
+
+class TestUsdDisplayDataOverride:
+    def test_user_display_data_override(self):
+        custom_display = {
+            "actin1": DisplayData(
+                name="CustomActin",
+                display_type=DISPLAY_TYPE.SPHERE,
+                color="#ff0000",
+                radius=5.0,
+            ),
+        }
+        converter = UsdConverter(
+            UsdData(
+                usd_file_path=ASCII_USD,
+                display_data=custom_display,
+                center=False,
+                trim_to_animation=False,
+            )
+        )
+        dd = converter._data.agent_data.display_data
+        assert "CustomActin" in dd
+        assert dd["CustomActin"].display_type == DISPLAY_TYPE.SPHERE
+        assert dd["CustomActin"].color == "#ff0000"
+        # Other types should still be auto-detected
+        assert "actin2" in dd
+        assert dd["actin2"].display_type == DISPLAY_TYPE.OBJ
+        # Verify types array uses display name (not prim name) for overridden agents
+        types = converter._data.agent_data.types[0]
+        assert "CustomActin" in types
+        assert "actin1" not in types
+        # Verify the full output type mapping is consistent
+        results = JsonWriter.format_trajectory_data(converter._data)
+        tm = results["trajectoryInfo"]["typeMapping"]
+        custom_entries = [
+            tid for tid in tm if tm[tid]["name"] == "CustomActin"
+        ]
+        assert len(custom_entries) == 1
+
+
+class TestUsdCentering:
+    def test_centered_positions_near_origin(self):
+        converter = UsdConverter(
+            UsdData(usd_file_path=ASCII_USD, center=True)
+        )
+        positions = converter._data.agent_data.positions
+        # Mean position across all agents at frame 0 should be near origin
+        mean_pos = np.mean(positions[0, :8], axis=0)
+        assert np.all(np.abs(mean_pos) < 5.0)

simulariumio/usd/__init__.py

@@ -0,0 +1,5 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+from .usd_converter import UsdConverter  # noqa: F401
+from .usd_data import UsdData  # noqa: F401