Added support for loading native object for openvdb

CHANGELOG

@@ -13,14 +13,21 @@ The rules for this file:
   * accompany each entry with github issue/PR number (Issue #xyz)
 
 -------------------------------------------------------------------------------
-MM/DD/2026 orbeckst
+MM/DD/2026 orbeckst, spyke7
 
   * 1.3.0
 
   Changes
 
   * update init signature for OpenDX.DXClass to include name and components
     as optional kwargs to streamline init in child classes (PR #179)
+
+  Enhancements
+
+  * Implemented loading of a Grid from a native object for OpenVDB (Issue #162,
+    PR #170)
+
+  Fixes
 
 
 05/22/2026 orbeckst, spyke7

gridData/OpenVDB.py

@@ -109,20 +109,21 @@
 @dataclass
 class DownCastTo:
     """:func:`~dataclasses.dataclass` decorator serving as a marker for a downcast.
-    
+
     This function is used to create a proxy for an OpenVDB grid type.
     The field :attr:`gridType` contains the OpenVDB grid type that it represents.
     :meth:`OpenVDBField._get_best_grid_type` selects a OpenVDB grid that best matches
     the numpy dtype of the data but in some cases, only target OpenVDB grid types are
     available that loose precision. In this case, this class wraps the orginal OpenVDB
     class to indicate that the downcast. For example, ::
-    
+
        np.dtype("int32"): ["Int32Grid", DownCastTo("FloatGrid")]
-       
+
     indicates that NumPy int32 data should be represented by a :class:`openvdb.Int32Grid`
     but if this is not available, a :class:`openvdb.FloatGrid` is used instead,
     which, however, is only able to represent a subset of all 32-bit integers.
     """
+
     gridType: str
 
 
@@ -142,7 +143,7 @@ class OpenVDBField(object):
 
       import gridData.OpenVDB as OpenVDB
 
-      vdb_field = OpenVDB.OpenVDBField(grid=np.ones((3, 4, 5)), 
+      vdb_field = OpenVDB.OpenVDBField(grid=np.ones((3, 4, 5)),
                                        origin=np.array([1.5, 0, 0]),
                                        delta=np.array([0.5, 0.5, 0.25]),
                                        name='density')
@@ -154,6 +155,32 @@ class OpenVDBField(object):
       g.export('output.vdb', format='vdb')
     """
 
+    # dtype maps for numpy to vdb
+    _DTYPES_NP2VDB = {
+        np.dtype("bool"): ["BoolGrid"],
+        np.dtype("int8"): ["Int32Grid", "FloatGrid"],
+        np.dtype("uint8"): ["Int32Grid", "FloatGrid"],
+        np.dtype("int16"): ["Int32Grid", "FloatGrid"],
+        np.dtype("uint16"): ["Int32Grid", "FloatGrid"],
+        np.dtype("int32"): ["Int32Grid", DownCastTo("FloatGrid")],
+        np.dtype("uint32"): [DownCastTo("Int32Grid"), DownCastTo("FloatGrid")],
+        np.dtype("int64"): ["Int64Grid", DownCastTo("FloatGrid")],
+        np.dtype("uint64"): ["Int64Grid", DownCastTo("FloatGrid")],
+        np.dtype("float16"): ["HalfGrid", "FloatGrid"],
+        np.dtype("float32"): ["FloatGrid"],
+        np.dtype("float64"): ["DoubleGrid", DownCastTo("FloatGrid")],
+    }
+
+    # dtype maps for vdb to numpy
+    _DTYPES_VDB2NP = {
+        "BoolGrid": np.dtype("bool"),
+        "Int32Grid": np.dtype("int32"),
+        "Int64Grid": np.dtype("int64"),
+        "FloatGrid": np.dtype("float32"),
+        "DoubleGrid": np.dtype("float64"),
+        "HalfGrid": np.dtype("float16"),
+    }
+
     def __init__(
         self,
         grid=None,
@@ -205,8 +232,13 @@ def __init__(
             self.metadata = {}
 
         if grid is not None:
-            self._populate(grid, origin, delta)
-            self.vdb_grid = self._create_openvdb_grid()
+            if isinstance(grid, vdb.GridBase):
+                self.vdb_grid = grid
+                self._extract_from_vdb_grid()
+            else:
+                self._populate(grid, origin, delta)
+                self.vdb_grid = self._create_openvdb_grid()
+
         else:
             self.grid = None
             self.origin = None
@@ -272,6 +304,57 @@ def native(self):
         """
         return self.vdb_grid
 
+    def _extract_from_vdb_grid(self):
+        """Extract numpy array, origin, delta from stored VDB grid.
+
+        This method converts the sparse VDB grid to a dense numpy array
+        and extracts the transform information.
+        """
+        for key in self.vdb_grid.metadata:
+            try:
+                self.metadata[key] = self.vdb_grid[key]
+            except (TypeError, ValueError) as e:
+                warnings.warn(
+                    f"Could not read metadata key '{key}' from VDB grid: {e}",
+                    UserWarning,
+                )
+
+        transformation = self.vdb_grid.transform
+
+        v_origin = np.array(transformation.indexToWorld([0, 0, 0]))
+        v_delta = np.array(transformation.indexToWorld([1, 1, 1])) - v_origin
+
+        self.origin = v_origin
+        self.delta = v_delta
+
+        try:
+            dtype = self._DTYPES_VDB2NP[type(self.vdb_grid).__name__]
+        except KeyError:
+            raise TypeError(
+                f"Unknown VDB grid type '{type(self.vdb_grid).__name__}', cannot map to a numpy dtype."
+            )
+
+        bbox = self.vdb_grid.evalActiveVoxelBoundingBox()
+
+        if bbox is None or any(bbox[1][i] < bbox[0][i] for i in range(3)):
+            warnings.warn(
+                "VDB grid has no active voxels (empty bounding box). Returning an empty array of shape (0, 0, 0).",
+                RuntimeWarning,
+            )
+            self.grid = np.zeros((0, 0, 0), dtype=dtype)
+            return
+
+        shape = tuple(np.array(bbox[1]) - np.array(bbox[0]) + 1)
+
+        self.grid = np.zeros(shape, dtype=dtype)
+        print(dtype)
+        self.vdb_grid.copyToArray(self.grid, ijk=bbox[0])
+
+        if not np.all(np.array(bbox[0]) == 0):
+            self.origin = np.array(
+                transformation.indexToWorld(np.array(bbox[0]).tolist())
+            )
+
     def _populate(self, grid, origin, delta):
         """Populate the field with grid data.
 
@@ -331,23 +414,8 @@ def _get_best_grid_type(self):
         TypeError
             If dtype is not supported or no suitable grid type is available
         """
-        datatypes = {
-            np.dtype("bool"): ["BoolGrid"],
-            np.dtype("int8"): ["Int32Grid", "FloatGrid"],
-            np.dtype("uint8"): ["Int32Grid", "FloatGrid"],
-            np.dtype("int16"): ["Int32Grid", "FloatGrid"],
-            np.dtype("uint16"): ["Int32Grid", "FloatGrid"],
-            np.dtype("int32"): ["Int32Grid", DownCastTo("FloatGrid")],
-            np.dtype("uint32"): [DownCastTo("Int32Grid"), DownCastTo("FloatGrid")],
-            np.dtype("int64"): ["Int64Grid", DownCastTo("FloatGrid")],
-            np.dtype("uint64"): ["Int64Grid", DownCastTo("FloatGrid")],
-            np.dtype("float16"): ["HalfGrid", "FloatGrid"],
-            np.dtype("float32"): ["FloatGrid"],
-            np.dtype("float64"): ["DoubleGrid", DownCastTo("FloatGrid")],
-        }
-
         try:
-            vdb_gridtypes = datatypes[self.grid.dtype]
+            vdb_gridtypes = self._DTYPES_NP2VDB[self.grid.dtype]
         except KeyError:
             raise TypeError(f"Data type {self.grid.dtype} not supported for VDB")
 

gridData/core.py

@@ -249,6 +249,21 @@ def __init__(self, grid=None, edges=None, origin=None, delta=None,
         self.interpolation_cval = None  # default to using min(grid)
 
         if grid is not None:
+            try:
+                # if a openvdb native grid is passed
+                import openvdb as vdb
+                if isinstance(grid, vdb.GridBase):
+                    vdb_field = OpenVDB.OpenVDBField(grid=grid)
+                    self.metadata = vdb_field.metadata
+                    self._load(
+                        grid=vdb_field.grid,
+                        origin=vdb_field.origin,
+                        delta=vdb_field.delta,
+                        metadata=vdb_field.metadata,
+                    )
+                    return
+            except ImportError:
+                pass
             if isinstance(grid, str):
                 # can probably safely try to load() it...
                 filename = grid

gridData/tests/test_vdb.py

@@ -392,6 +392,104 @@ def test_from_native_grid_shape_values_and_dimension(self, grid345):
         world = native_grid.transform.indexToWorld((0, 0, 0))
         assert_allclose([world[0], world[1], world[2]], g.origin, rtol=1e-5)
 
+    def test_file_roundtrip_native_vdbgrid(self, tmpdir, grid345):
+        data, g = grid345
+        g.metadata["name"] = "new_density"
+
+        outfile = str(tmpdir / "roundtrip.vdb")
+        g.export(outfile)
+
+        grids, _ = vdb.readAll(outfile)
+        assert len(grids) == 1
+
+        grid_vdb = grids[0]
+        new_vdb_grid = Grid(grid=grid_vdb)
+        assert_allclose(new_vdb_grid.grid, g.grid, rtol=1e-5)
+        assert_allclose(new_vdb_grid.origin, g.origin, rtol=1e-5)
+        assert_allclose(new_vdb_grid.delta, g.delta, rtol=1e-5)
+        assert new_vdb_grid.metadata["name"] == "new_density"
+        assert new_vdb_grid.grid.dtype == np.dtype("float32")
+        assert_allclose(new_vdb_grid.grid, data, rtol=1e-5)
+
+    def test_extract_from_vdb_grid(self, grid345):
+        data, g = grid345
+        g.metadata["name"] = "new_density"
+
+        native = g.convert_to("vdb")
+        new_vdb_grid = Grid(grid=native)
+
+        assert_allclose(new_vdb_grid.grid, g.grid, rtol=1e-5)
+        assert_allclose(new_vdb_grid.origin, g.origin, rtol=1e-5)
+        assert_allclose(new_vdb_grid.delta, g.delta, rtol=1e-5)
+        assert new_vdb_grid.metadata["name"] == "new_density"
+        assert new_vdb_grid.grid.dtype == np.dtype("float32")
+        assert_allclose(new_vdb_grid.grid, data, rtol=1e-5)
+
+    @pytest.mark.parametrize(
+        "vdb_type,np_dtype", list(gridData.OpenVDB.OpenVDBField._DTYPES_VDB2NP.items())
+    )
+    def test_extract_dtype_roundtrip(self, vdb_type, np_dtype):
+        vdb_cls = getattr(vdb, vdb_type, None)
+        if vdb_cls is None:
+            pytest.skip(f"{vdb_type} not available in this openvdb build")
+
+        native = vdb_cls()
+        native.name = "test"
+        acc = native.getAccessor()
+        acc.setValueOn((0, 0, 0), True if np_dtype == np.dtype("bool") else 1)
+        acc.setValueOn((1, 1, 1), True if np_dtype == np.dtype("bool") else 2)
+
+        field = gridData.OpenVDB.OpenVDBField(grid=native)
+
+        assert field.grid.dtype == np_dtype
+        assert field.grid.shape != (0, 0, 0)
+
+    def test_extract_unknown_vdb_type_warns(self):
+        native = vdb.FloatGrid()
+        acc = native.getAccessor()
+        acc.setValueOn((0, 0, 0), 1.0)
+
+        patched = {
+            k: v
+            for k, v in gridData.OpenVDB.OpenVDBField._DTYPES_VDB2NP.items()
+            if k != "FloatGrid"
+        }
+        with patch.object(gridData.OpenVDB.OpenVDBField, "_DTYPES_VDB2NP", patched):
+            with pytest.raises(TypeError, match="Unknown VDB grid type"):
+                field = gridData.OpenVDB.OpenVDBField(grid=native)
+
+    def test_extract_empty_vdb_grid_warns(self):
+        native = vdb.FloatGrid()
+        native.clear()
+
+        with pytest.warns(RuntimeWarning, match="no active voxels"):
+            field = gridData.OpenVDB.OpenVDBField(grid=native)
+
+        assert field.grid.shape == (0, 0, 0)
+
+    def test_extract_unreadable_metadata_warns(self, grid345):
+        data, g = grid345
+        g.metadata["readable"] = "hello"
+        g.metadata["factor"] = 42
+
+        native = g.convert_to("vdb")
+
+        original_getitem = native.__class__.__getitem__
+
+        def patched_getitem(self, key):
+            if key == "factor":
+                raise TypeError("unsupported metadata type")
+            return original_getitem(self, key)
+
+        with patch.object(native.__class__, "__getitem__", patched_getitem):
+            with pytest.warns(
+                UserWarning, match="Could not read metadata key 'factor'"
+            ):
+                field = gridData.OpenVDB.OpenVDBField(grid=native)
+
+        assert field.metadata.get("readable") == "hello"
+        assert "factor" not in field.metadata
+
 
 @pytest.mark.skipif(
     not HAS_OPENVDB, reason="Need openvdb to test import error handling"