Tutorial_110_Graph_Property/main.cpp

This example shows how to add per-vertex/per-edge properties to a graph, and how to access existing properties.

/********************************************************************
 * Copyright (C) 2015 Liangliang Nan <liangliang.nan@gmail.com>
 * https://3d.bk.tudelft.nl/liangliang/
 *
 * This file is part of Easy3D. If it is useful in your research/work,
 * I would be grateful if you show your appreciation by citing it:
 * ------------------------------------------------------------------
 *      Liangliang Nan.
 *      Easy3D: a lightweight, easy-to-use, and efficient C++ library
 *      for processing and rendering 3D data.
 *      Journal of Open Source Software, 6(64), 3255, 2021.
 * ------------------------------------------------------------------
 *
 * Easy3D is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License Version 3
 * as published by the Free Software Foundation.
 *
 * Easy3D is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 ********************************************************************/
 
#include <easy3d/core/graph.h>
#include <easy3d/util/initializer.h>
 
using namespace easy3d;
 
 
// the graph created in the previous tutorial (so you can skip it)
Graph* old_graph_from_previous_example() {
    // Create a graph
    auto graph = new Graph;
 
    // Add 4 vertices
    Graph::Vertex v0 = graph->add_vertex(vec3(0, 0, 0));
    Graph::Vertex v1 = graph->add_vertex(vec3(1, 0, 0));
    Graph::Vertex v2 = graph->add_vertex(vec3(0, 1, 0));
    Graph::Vertex v3 = graph->add_vertex(vec3(0, 0, 1));
 
    // Add some edges
    graph->add_edge(v0, v1); // e0
    graph->add_edge(v1, v2); // e1
    graph->add_edge(v2, v3); // e2
    graph->add_edge(v3, v0); // e3
    graph->add_edge(v1, v3); // e4
 
    return graph;
}
 
 
int main(int argc, char** argv) {
    // initialize Easy3D.
    initialize();
 
    Graph* graph = old_graph_from_previous_example();
 
    auto points = graph->vertex_property<vec3>("v:point");
 
    // We add a per-vertex property "v:color" to assign a color to each vertex
    auto colors = graph->add_vertex_property<vec3>("v:color");
    for (auto v : graph->vertices()) {
        // We assign each vertex a color that is equal to his position (you should
        // assign a more meaningful color in practice).
        colors[v] = points[v];
        std::cout << "vertex: " << v << ", position: " << points[v] << ", color: " << colors[v] << std::endl;
    }
 
    // We add a per-edge property "e:length" to store the edge lengths
    auto lengths = graph->add_edge_property<float>("e:length");
    for (auto e : graph->edges()) {
        lengths[e] = graph->edge_length(e);
        std::cout << "edge: " << e << ", length: " << lengths[e] << std::endl;
    }
 
    delete graph;
 
    return EXIT_SUCCESS;
}