fix(Mesh): add in SolidMesh a method to get local indices of edge vertices (#529)

Author: panquez

bindings/python/src/mesh/core/solid_mesh.h

@@ -105,7 +105,9 @@
         .def( "polyhedron_attribute_manager",                                  \
             &SolidMesh##dimension##D::polyhedron_attribute_manager,            \
             pybind11::return_value_policy::reference )                         \
-        .def( "bounding_box", &SolidMesh##dimension##D::bounding_box )
+        .def( "bounding_box", &SolidMesh##dimension##D::bounding_box )         \
+        .def( "edge_vertices_in_polyhedron",                                   \
+            &SolidMesh##dimension##D::edge_vertices_in_polyhedron )
 
 namespace geode
 {

include/geode/mesh/core/solid_mesh.h

@@ -492,6 +492,17 @@ namespace geode
         PolyhedraAroundFacet polyhedra_from_facet_vertices(
             PolyhedronFacetVertices facet_vertices ) const;
 
+        /*!
+         * Get the local indices in the polyhedra of both edge vertices.
+         * @param[in] polyhedron_id Index of polyhedron.
+         * @param[in] edge_vertices Global indices of the two edge vertices.
+         * @details If the vertices are not in the polyhedron, NO_LID is
+         * returned.
+         */
+        std::array< local_index_t, 2 > edge_vertices_in_polyhedron(
+            index_t polyhedron_id,
+            const std::array< index_t, 2 >& edge_vertices ) const;
+
         bool are_edges_enabled() const;
 
         void enable_edges() const;

src/geode/mesh/core/solid_mesh.cpp

@@ -1244,6 +1244,29 @@ namespace geode
         return borders;
     }
 
+    template < index_t dimension >
+    std::array< local_index_t, 2 >
+        SolidMesh< dimension >::edge_vertices_in_polyhedron(
+            index_t polyhedron_id,
+            const std::array< index_t, 2 >& edge_vertices ) const
+    {
+        std::array< local_index_t, 2 > result{ { NO_LID, NO_LID } };
+
+        const auto vertices = polyhedron_vertices( polyhedron_id );
+        for( const auto v : LRange{ nb_polyhedron_vertices( polyhedron_id ) } )
+        {
+            if( vertices[v] == edge_vertices[0] && result[0] == NO_LID )
+            {
+                result[0] = v;
+            }
+            else if( vertices[v] == edge_vertices[1] && result[1] == NO_LID )
+            {
+                result[1] = v;
+            }
+        }
+        return result;
+    }
+
     template < index_t dimension >
     AttributeManager&
         SolidMesh< dimension >::polyhedron_attribute_manager() const