Merge pull request #1066 from Geode-solutions/fix/surface-segment

fix(SurfaceMesh): create Segment from PolygonEdge

Author: MelchiorSchuh

include/geode/geometry/basic_objects/triangle.hpp

@@ -84,6 +84,7 @@ namespace geode
         [[nodiscard]] const std::array< PointType, 3 >& vertices() const;
         [[nodiscard]] BoundingBox< dimension > bounding_box() const;
         [[nodiscard]] local_index_t longest_edge_index() const;
+        [[nodiscard]] local_index_t smallest_edge_index() const;
         [[nodiscard]] double minimum_height() const;
         [[nodiscard]] bool is_degenerated() const;
         [[nodiscard]] std::string string() const;

include/geode/mesh/core/surface_mesh.hpp

@@ -40,6 +40,7 @@ namespace geode
     FORWARD_DECLARATION_DIMENSION_CLASS( Polygon );
     FORWARD_DECLARATION_DIMENSION_CLASS( Vector );
     FORWARD_DECLARATION_DIMENSION_CLASS( BoundingBox );
+    FORWARD_DECLARATION_DIMENSION_CLASS( Segment );
     FORWARD_DECLARATION_DIMENSION_CLASS( SurfaceEdges );
     FORWARD_DECLARATION_DIMENSION_CLASS( SurfaceMeshBuilder );
 
@@ -404,6 +405,9 @@ namespace geode
         [[nodiscard]] std::optional< PolygonEdge > polygon_edge_from_vertices(
             index_t from_vertex_id, index_t to_vertex_id ) const;
 
+        [[nodiscard]] Segment< dimension > segment(
+            const PolygonEdge& polygon_edge ) const;
+
         /*!
          * Find the polygon edges corresponding to a pair of vertex indices.
          * @return Local indices of the edges found

src/geode/geometry/basic_objects/triangle.cpp

@@ -256,6 +256,27 @@ namespace geode
         return max_length_edge_id;
     }
 
+    template < typename PointType, index_t dimension >
+    local_index_t
+        GenericTriangle< PointType, dimension >::smallest_edge_index() const
+    {
+        local_index_t min_length_edge_id{ NO_LID };
+        auto edge_min_length = std::numeric_limits< double >::max();
+        for( const auto edge_id : LRange{ 3 } )
+        {
+            const auto next_vertex = edge_id == 2 ? 0 : edge_id + 1;
+            const Point< dimension >& point0 = vertices_.at( edge_id );
+            const Point< dimension >& point1 = vertices_.at( next_vertex );
+            const auto edge_length = point_point_distance( point0, point1 );
+            if( edge_length < edge_min_length )
+            {
+                min_length_edge_id = edge_id;
+                edge_min_length = edge_length;
+            }
+        }
+        return min_length_edge_id;
+    }
+
     template < typename PointType, index_t dimension >
     double GenericTriangle< PointType, dimension >::minimum_height() const
     {

src/geode/mesh/core/surface_mesh.cpp

@@ -911,6 +911,14 @@ namespace geode
         return std::nullopt;
     }
 
+    template < index_t dimension >
+    Segment< dimension > SurfaceMesh< dimension >::segment(
+        const PolygonEdge& polygon_edge ) const
+    {
+        const auto vertices = polygon_edge_vertices( polygon_edge );
+        return { this->point( vertices[0] ), this->point( vertices[1] ) };
+    }
+
     template < index_t dimension >
     PolygonsAroundEdge SurfaceMesh< dimension >::polygons_from_edge_vertices(
         absl::Span< const index_t > edge_vertices ) const