Store opposite edges in a Map

QTProject/subdivision.cpp

@@ -93,6 +93,26 @@ void Subdivision::subdivide(Mesh *mesh, int level) {
     }
 }
 
+void insert_edge(QMap<Triangle, QVector<Triangle::Edge>> &opposite_edges, const Triangle &triangle, const Triangle::Edge &edge_a, const Triangle::Edge &edge_b) {
+    QVector<Triangle::Edge> edges = opposite_edges.value(triangle, QVector<Triangle::Edge>());
+    edges.resize(3);
+    switch (edge_a.name) {
+        case Triangle::Edge::Name::uv:
+            edges[0] = edge_b;
+            break;
+        case Triangle::Edge::Name::vw:
+            edges[1] = edge_b;
+            break;
+        case Triangle::Edge::Name::wu:
+            edges[2] = edge_b;
+            break;
+        default:
+            qWarning() << "got" << edge_a.name << "as edge!";
+            break;
+    }
+    opposite_edges.insert(triangle, edges);
+}
+
 /**
  * @brief Subdivision::precomputeTables
  * @param mesh
@@ -123,6 +143,9 @@ Subdivision::Tables Subdivision::precomputeTables(Input input) {
     //compute edge table
     //Format: first two entries: edge vertices. last two entries: distant vertices.
 
+    // for each triangle the edges of the neighbor triangles are stored.
+    // First the edge shared with the triangles uv edge, then vw and wu.
+    QMap<Triangle, QVector<Triangle::Edge>> opposite_edges;
     unsigned int nib_offset = vb.length();//offset in new index buffer for edge vertices
     for (int i = 0; i < triangles.length(); i++){
         //schaue alle dreiecke an
@@ -139,43 +162,28 @@ Subdivision::Tables Subdivision::precomputeTables(Input input) {
          */
 
         Triangle::Edge edge_a, edge_b;
-        // These will hold the edges of the triangles next to the current one. uv will hold the edge shared with the current triangle's uv edge.
-        Triangle::Edge uv, vw, wu;
-        for (int j = 0; j < triangles.length(); j++){
-            if (j != i) {
+        for (int j = i + 1; j < triangles.length(); j++){
             if (triangle.get_shared_edge(triangles[j], edge_a, edge_b)) {
-                    switch (edge_a.name) {
-                        case Triangle::Edge::Name::uv:
-                            uv = edge_b;
-                            break;
-                        case Triangle::Edge::Name::vw:
-                            vw = edge_b;
-                            break;
-                        case Triangle::Edge::Name::wu:
-                            wu = edge_b;
-                            break;
-                        default:
-                            qWarning() << "got" << edge_a.name << "as edge!";
-                            break;
-                    }
-                }
+                insert_edge(opposite_edges, triangle, edge_a, edge_b);
+                insert_edge(opposite_edges, triangles[j], edge_b, edge_a);
             }
         }
 
+        QVector<Triangle::Edge> opposite = opposite_edges.value(triangle);
         tables.edge_indices.push_back(triangle.u_idx());
         tables.edge_indices.push_back(triangle.v_idx());
         tables.edge_indices.push_back(triangle.w_idx());
-        tables.edge_indices.push_back(uv.c);
+        tables.edge_indices.push_back(opposite[0].c);
 
         tables.edge_indices.push_back(triangle.v_idx());
         tables.edge_indices.push_back(triangle.w_idx());
         tables.edge_indices.push_back(triangle.u_idx());
-        tables.edge_indices.push_back(vw.c);
+        tables.edge_indices.push_back(opposite[1].c);
 
         tables.edge_indices.push_back(triangle.w_idx());
         tables.edge_indices.push_back(triangle.u_idx());
         tables.edge_indices.push_back(triangle.v_idx());
-        tables.edge_indices.push_back(wu.c);
+        tables.edge_indices.push_back(opposite[2].c);
 
         //add indices to new index buffer
         tables.index_buffer.push_back(triangle.u_idx());