added convert_to in core.py, checked for grid and origin

Author: spyke7

gridData/OpenVDB.py

@@ -186,11 +186,17 @@ def _populate(self, grid, origin, delta):
 
         """
         self.grid = numpy.asarray(grid)
-        if grid.ndim != 3:
+        if self.grid.ndim != 3:
             raise ValueError(f"OpenVDB only supports 3D grids, got {grid.ndim}D")
 
         self.grid = numpy.ascontiguousarray(self.grid)
 
+        if origin is None:
+            raise ValueError("origin must be provided for VDB export")
+
+        if len(origin) != 3:
+            raise ValueError("origin must be length-3")
+
         self.origin = numpy.asarray(origin)
 
         # Handle delta: could be 1D array or diagonal matrix

gridData/core.py

@@ -622,6 +622,40 @@ def _load_plt(self, filename, **kwargs):
         grid, edges = g.histogramdd()
         self._load(grid=grid, edges=edges, metadata=self.metadata)
 
+    def convert_to(self, format_specifier, tolerance=None, **kwargs):
+        """generates an instance of the native object for a given format
+        
+        Implemented formats:
+        
+        vdb
+            :mod:`OpenVDB`
+            
+        Parameters
+        ----------
+        format_specifier : str 
+            vdb, etc
+
+        Returns
+        -------
+        native object
+        
+        """
+        formats = ("mrc", "vdb")
+        if (format_specifier.lower() == formats[1]):
+            grid_name = self.metadata.get("name", "density")
+            vdb_field  = OpenVDB.OpenVDBField(
+                grid=self.grid,
+                origin=self.origin,
+                delta=self.delta,
+                name=grid_name,
+                tolerance=tolerance,
+                metadata=self.metadata
+            )
+            
+            return vdb_field.vdb_grid
+        
+        raise ValueError(f"Unsupported convert_to format : {format_specifier}")
+
     def export(
         self, filename, file_format=None, type=None, typequote='"', tolerance=None
     ):

gridData/tests/test_vdb.py

@@ -336,6 +336,32 @@ def test_openvdb_field_empty_initialization(self, tmpdir):
 
         assert tmpdir.join("empty_init.vdb").exists()
 
+    def test_vdb_origin_none_raises(self):
+        data = np.ones((5, 5, 5))
+
+        with pytest.raises(ValueError, match="origin must be provided"):
+            gridData.OpenVDB.OpenVDBField(grid=data, origin=None, delta=(1, 1, 1))
+
+    def test_vdb_origin_wrong_length_raises(self):
+        data = np.ones((5, 5, 5))
+
+        with pytest.raises(ValueError, match="length-3"):
+            gridData.OpenVDB.OpenVDBField(grid=data, origin=(0, 0), delta=(1, 1, 1))
+
+    def test_vdb_write_without_grid_raises(self, tmpdir):
+        vdb_field = gridData.OpenVDB.OpenVDBField()
+
+        outfile = str(tmpdir / "test.vdb")
+
+        with pytest.raises(ValueError, match="No grid data"):
+            vdb_field.write(str(outfile))
+
+    def test_grid_convert_to_vdb(self, grid345):
+        data, g = grid345
+        native = g.convert_to("vdb")
+
+        assert isinstance(native, vdb.GridBase)
+
 
 @pytest.mark.skipif(
     not HAS_OPENVDB, reason="Need openvdb to test import error handling"