semistructured_grids.ipynb

yt.patch

diff --git a/yt/data_objects/index_subobjects/unstructured_mesh.py b/yt/data_objects/index_subobjects/unstructured_mesh.py
index 375a2ae19..e864498f7 100644
--- a/yt/data_objects/index_subobjects/unstructured_mesh.py
+++ b/yt/data_objects/index_subobjects/unstructured_mesh.py
@@ -1,4 +1,5 @@
 import numpy as np
+from yt.geometry.selection_routines import convert_mask_to_indices
 
 from yt.data_objects.selection_objects.data_selection_objects import (
     YTSelectionContainer,
@@ -163,6 +164,18 @@ class SemiStructuredMesh(UnstructuredMesh):
         elif field == "dz":
             return self._current_chunk.fwidth[:, 2]
 
+    def select_icoords(self, dobj):
+        mask = self._get_selector_mask(dobj.selector)
+        if mask is None:
+            return np.empty((0, 3), dtype="int64")
+        indices = np.unravel_index(np.where(mask), [64, 64, 64])
+        mask = np.zeros((64, 64, 64), dtype="bool")
+        mask[indices] = True
+        coords = convert_mask_to_indices(mask, self._last_count)
+        start_index = np.array([0, 0, 0], dtype="i8")
+        coords += start_index[None, :]
+        return coords
+
     def select_fwidth(self, dobj):
         mask = self._get_selector_mask(dobj.selector)
         if mask is None:
diff --git a/yt/loaders.py b/yt/loaders.py
index e63069d22..faca50925 100644
--- a/yt/loaders.py
+++ b/yt/loaders.py
@@ -805,7 +805,7 @@ def load_hexahedral_mesh(
     )
     from yt.frontends.stream.definitions import process_data, set_particle_types
 
-    domain_dimensions = np.ones(3, "int32") * 2
+    domain_dimensions = np.ones(3, "int32") * 64
     nprocs = 1
     if bbox is None:
         bbox = np.array([[0.0, 1.0], [0.0, 1.0], [0.0, 1.0]], "float64")
@@ -1157,7 +1157,7 @@ def load_unstructured_mesh(
     from yt.frontends.stream.definitions import process_data, set_particle_types
 
     dimensionality = coordinates.shape[1]
-    domain_dimensions = np.ones(3, "int32") * 2
+    domain_dimensions = np.ones(3, "int32") * 64
     nprocs = 1
 
     if elem_data is None and node_data is None: