Add support for obj files with multiple connected components

Source/obj/WorldObject.cpp

@@ -8,6 +8,36 @@ struct pair_hash {
     }
 };
 
+std::vector<std::vector<int>> ConnectedComponents(const Graph& G) {
+    std::vector<std::vector<int>> components;
+    std::vector<bool> visited(G.GetNumVertices(), false);
+    list<int> L;
+
+    for (int i = 0; i < visited.size(); i++) {
+        // if condition should only be true for the first element in
+        // a new connected component
+        if (!visited[i]) {
+            components.emplace_back();
+            // Breadth First Search
+            L.push_back(i);
+            while (not L.empty()) {
+                int u = L.back();
+                L.pop_back();
+                if (visited[u]) continue;
+
+                visited[u] = true;
+                components.back().push_back(u);
+
+                for (int v : G.AdjList(u)) {
+                    L.push_back(v);
+                }
+            }
+        }
+    }
+
+    return components;
+}
+
 WorldObject::WorldObject(juce::InputStream& stream) {
     tinyobj::ObjReaderConfig reader_config;
     tinyobj::ObjReader reader;
@@ -16,35 +46,6 @@ WorldObject::WorldObject(juce::InputStream& stream) {
 
     vs = reader.GetAttrib().vertices;
 	numVertices = vs.size() / 3;
-    std::vector<tinyobj::shape_t> shapes = reader.GetShapes();
-    
-    std::unordered_set<std::pair<int, int>, pair_hash> edge_set;
-	for (auto& shape : shapes) {
-        int i = 0;
-        int face = 0;
-        while (i < shape.mesh.indices.size()) {
-            int prevVertex = -1;
-			for (int j = 0; j < shape.mesh.num_face_vertices[face]; j++) {
-				int vertex = shape.mesh.indices[i].vertex_index;
-				if (prevVertex != -1) {
-					edge_set.insert(std::make_pair(prevVertex, vertex));
-				}
-				prevVertex = vertex;
-				i++;
-			}
-            face++;
-        }
-	}
-
-    std::list<std::pair<int, int>> edge_list;
-
-    for (auto& edge : edge_set) {
-        edge_list.push_back(edge);
-    }
-
-    Graph graph(numVertices, edge_list);
-    pair<list<int>, double> solution = ChinesePostman(graph);
-    list<int>& path = solution.first;
 
     double x = 0.0, y = 0.0, z = 0.0;
     double max = 0.0;
@@ -73,8 +74,73 @@ WorldObject::WorldObject(juce::InputStream& stream) {
         vs[i * 3 + 2] = (vs[i * 3 + 2] - z) / max;
     }
 
+    std::vector<tinyobj::shape_t> shapes = reader.GetShapes();
+    
+    std::unordered_set<std::pair<int, int>, pair_hash> edge_set;
+	for (auto& shape : shapes) {
+        int i = 0;
+        int face = 0;
+        while (i < shape.mesh.indices.size()) {
             int prevVertex = -1;
-    for (auto& vertex : path) {
+			for (int j = 0; j < shape.mesh.num_face_vertices[face]; j++) {
+				int vertex = shape.mesh.indices[i].vertex_index;
+				if (prevVertex != -1) {
+					edge_set.insert(std::make_pair(prevVertex, vertex));
+				}
+				prevVertex = vertex;
+				i++;
+			}
+            face++;
+        }
+	}
+
+    std::list<std::pair<int, int>> edge_list;
+
+    for (auto& edge : edge_set) {
+        edge_list.push_back(edge);
+    }
+
+    Graph graph(numVertices, edge_list);
+
+    std::vector<std::vector<int>> connected_components = ConnectedComponents(graph);
+
+    for (auto& connected_component : connected_components) {
+        std::vector<bool> present_vertices(graph.GetNumVertices(), false);
+
+        for (int vertex : connected_component) {
+            present_vertices[vertex] = true;
+        }
+
+        std::unordered_map<int, int> obj_to_graph_vertex;
+        std::unordered_map<int, int> graph_to_obj_vertex;
+
+        int count = 0;
+        for (int i = 0; i < graph.GetNumVertices(); i++) {
+            if (present_vertices[i]) {
+                obj_to_graph_vertex[i] = i - count;
+                graph_to_obj_vertex[i - count] = i;
+            } else {
+                count++;
+            }
+        }
+
+        std::list<std::pair<int, int>> sub_edge_list;
+
+        for (int obj_start : connected_component) {
+            for (int obj_end : graph.AdjList(obj_start)) {
+                int graph_start = obj_to_graph_vertex[obj_start];
+                int graph_end = obj_to_graph_vertex[obj_end];
+                sub_edge_list.push_back(std::make_pair(graph_start, graph_end));
+            }
+        }
+
+        Graph subgraph(connected_component.size(), sub_edge_list);
+        pair<list<int>, double> solution = ChinesePostman(subgraph);
+        list<int>& path = solution.first;
+
+        int prevVertex = -1;
+        for (auto& graph_vertex : path) {
+            int vertex = graph_to_obj_vertex[graph_vertex];
             if (prevVertex != -1) {
                 double x1 = vs[prevVertex * 3];
                 double y1 = vs[prevVertex * 3 + 1];
@@ -87,4 +153,5 @@ WorldObject::WorldObject(juce::InputStream& stream) {
             }
             prevVertex = vertex;
         }
+    }
 }