Add method for neighbor detection

QTProject/triangle.cpp

@@ -42,6 +42,61 @@ int Triangle::w_idx() const {
     return w_;
 }
 
+bool Triangle::get_shared_edge(Triangle other, Shared_Edge &edge) const {
+    if (get_shared_edge_(other, edge)) {
+        return true;
+    }
+
+    other.rotate_indices();
+    if (get_shared_edge_(other, edge)) {
+        return true;
+    }
+
+    other.rotate_indices();
+    return get_shared_edge_(other, edge);
+}
+
+bool Triangle::get_shared_edge_(const Triangle &other, Shared_Edge &edge) const {
+    if (u().samePos(other.u())) {
+        if (v().samePos(other.w())) {
+            edge.a1 = u_idx();
+            edge.b1 = other.u_idx();
+
+            edge.a2 = v_idx();
+            edge.b2 = other.w_idx();
+
+            edge.a3 = w_idx();
+            edge.b3 = other.v_idx();
+
+            return true;
+        } else if (w().samePos(other.v())) {
+            edge.a1 = u_idx();
+            edge.b1 = other.u_idx();
+
+            edge.a2 = w_idx();
+            edge.b2 = other.v_idx();
+
+            edge.a3 = v_idx();
+            edge.b3 = other.w_idx();
+
+            return true;
+        }
+    } else if (v().samePos(other.u()) && w().samePos(other.w())) {
+        edge.a1 = v_idx();
+        edge.b1 = other.u_idx();
+
+        edge.a2 = w_idx();
+        edge.b2 = other.w_idx();
+
+        edge.a3 = u_idx();
+        edge.b3 = other.v_idx();
+
+        return true;
+    }
+
+    return false;
+}
+
 Triangle &Triangle::operator=(const Triangle &other) {
     this->vertex_buffer_ = other.vertex_buffer_;
     this->u_ = other.u_;
@@ -76,6 +131,13 @@ bool Triangle::operator<(const Triangle &other) const {
     return false;
 }
 
+void Triangle::rotate_indices() {
+    unsigned int a = u_;
+    u_ = v_;
+    v_ = w_;
+    w_ = a;
+}
+
 QDebug operator<<(QDebug d, const Triangle &triangle) {
     QDebugStateSaver saver(d);
     d.nospace() << "Triangle(" << triangle.u_idx() << ", " << triangle.v_idx() << ", " << triangle.w_idx() << "; " << triangle.u().pos << ", " << triangle.v().pos << ", " << triangle.w().pos << ")";

QTProject/triangle.h

@@ -8,6 +8,22 @@
 
 class Triangle {
     public:
+        /**
+         * Stores the indices of the shared edge of two triangles as well as the other two indices.
+         *
+         * a_* are the indices of the first triangle, b_* those of the second triangle.
+         *
+         * The vertices at a_1 and b_1 are at the same position as are those at a_2 and b_2.
+         */
+        struct Shared_Edge {
+            unsigned int a1;
+            unsigned int b1;
+            unsigned int a2;
+            unsigned int b2;
+            unsigned int a3;
+            unsigned int b3;
+        };
+
         Triangle();
         Triangle(const Triangle &other);
         Triangle(const QVector<Vertex> &vertex_buffer, int u, int v, int w);
@@ -20,6 +36,8 @@ class Triangle {
         int v_idx() const;
         int w_idx() const;
 
+        bool get_shared_edge(Triangle other, Shared_Edge &edge) const;
+
         Triangle &operator=(const Triangle &other);
 
         // == and < both ignore the vertex buffer, they only compare indices.
@@ -32,6 +50,9 @@ class Triangle {
         int u_;
         int v_;
         int w_;
+
+        void rotate_indices();
+        bool get_shared_edge_(const Triangle &other, Shared_Edge &edge) const;
 };
 
 QDebug operator<<(QDebug d, const Triangle &triangle);