adds two examples to the cookbook. they might too specific

docs/cookbook.rst

@@ -17,3 +17,68 @@ Laplacian Smoothing with Feature Edges
 --------------------------------------
 
 TODO
+
+
+Extracting Edges as Segments
+--------------------------
+
+::
+
+    // given:
+    // pm::Mesh m;
+    // pm::vertex_attribute<tg::pos3> pos;
+    
+    // functional style
+    auto edges0 = m.edges().map([&](pm::edge_handle e) {
+            return tg::segment3(pos[e.vertexA()], pos[e.vertexB()]);
+        }).to_vector();
+    
+    // or
+    
+    // classical style
+    std::vector<tg::segment3> edges;
+    edges.reserve(m.edges().size());
+    for (auto const& e : m.edges().to_vector())
+        edges.emplace_back(tg::segment3(pos[e.vertexA()], pos[e.vertexB()]));
+
+
+Add Triangle Faces to Mesh
+--------------------------
+
+::
+
+    pm::Mesh m;
+    auto pos = pm::vertex_attribute<tg::pos3>(m);
+    
+    const auto n = 10;
+    std::vector<tg::triangle3> tris;
+    tris.reserve(n);
+
+    // some box to sample random positions
+    const auto box = tg::box3(tg::aabb3({-n, -n, -n}, {n, n, n}));
+    
+    tg::rng rng;
+    // create random triangles
+    for (auto i = 0u; i < n; ++i)
+        tris.emplace_back(tg::triangle3(tg::uniform(rng, box), tg::uniform(rng, box), tg::uniform(rng, box)));
+
+    for (auto const& tri : tris)
+    {
+        /// add vertices to topology
+        const auto vh0 = m.vertices().add();
+        const auto vh1 = m.vertices().add();
+        const auto vh2 = m.vertices().add();
+
+        /// add vertex positions
+        pos[vh0] = tri.pos0;
+        pos[vh1] = tri.pos1;
+        pos[vh2] = tri.pos2;
+
+        /// add face to topology
+        m.faces().add(vh0, vh1, vh2);
+    }
+    
+    // note that this will generate a triangle soup only. to obtain a sound mesh, deduplicate it
+    // triangles that share a certain position will then be properly connected
+    pm::deduplicate(m, pos);
+    m.compactify();