Reduce ORANGE state size for models with background volumes (#2139)

Set max_intersections to zero for background volumes

Author: elliottbiondo

src/orange/detail/UnitInserter.cc

@@ -409,15 +409,26 @@ VolumeRecord UnitInserter::insert_volume(SurfacesRecord const& surf_record,
     auto params_cref = make_const_ref(*orange_data_);
     LocalSurfaceVisitor visit_surface(params_cref, surf_record);
 
-    // Mark as 'simple safety' if all the surfaces are simple
+    // Mark this volume as "simple safety" if all of its constituent surfaces
+    // support it, even in the case where the volume is implicit
     bool simple_safety = true;
-    size_type max_intersections = 0;
-
     for (LocalSurfaceId sid : v.faces)
     {
         simple_safety = simple_safety
                         && visit_surface(SimpleSafetyGetter{}, sid);
-        max_intersections += visit_surface(NumIntersectionGetter{}, sid);
+    }
+
+    // Calculate the max_intersection for the volume by summing up the
+    // max_intersection for all constituent surfaces. If the volume is
+    // background (implicit), no intersection is possible, thus
+    // max_intersections is zero
+    size_type max_intersections = 0;
+    if (v.zorder != ZOrder::background)
+    {
+        for (LocalSurfaceId sid : v.faces)
+        {
+            max_intersections += visit_surface(NumIntersectionGetter{}, sid);
+        }
     }
 
     static logic_int const nowhere_logic[] = {logic::ltrue, logic::lnot};

test/orange/OrangeJson.test.cc

@@ -748,7 +748,7 @@ TEST_F(InputBuilderTest, bgspheres)
 
     OrangeParamsOutput out(this->geometry());
     EXPECT_JSON_EQ(
-        R"json({"_category":"internal","_label":"orange","scalars":{"max_depth":1,"max_faces":3,"max_intersections":6,"max_logic_depth":1,"tol":{"abs":1e-05,"rel":1e-05}},"sizes":{"bih":{"bboxes":4,"inner_nodes":1,"leaf_nodes":2,"local_volume_ids":3},"connectivity_records":3,"daughters":0,"local_surface_ids":6,"local_volume_ids":3,"logic_ints":5,"real_ids":3,"reals":9,"rect_arrays":0,"simple_units":1,"surface_types":3,"transforms":0,"universe_indices":1,"universe_types":1,"volume_records":4},"surfaces":{"label":["[EXTERIOR]@global","top@s","bottom@s"]}})json",
+        R"json({"_category":"internal","_label":"orange","scalars":{"max_depth":1,"max_faces":3,"max_intersections":2,"max_logic_depth":1,"tol":{"abs":1e-05,"rel":1e-05}},"sizes":{"bih":{"bboxes":4,"inner_nodes":1,"leaf_nodes":2,"local_volume_ids":3},"connectivity_records":3,"daughters":0,"local_surface_ids":6,"local_volume_ids":3,"logic_ints":5,"real_ids":3,"reals":9,"rect_arrays":0,"simple_units":1,"surface_types":3,"transforms":0,"universe_indices":1,"universe_types":1,"volume_records":4},"surfaces":{"label":["[EXTERIOR]@global","top@s","bottom@s"]}})json",
         to_string(out));
 }