CGAL-绘制Voronoi图\泰森多边形

综述

前些日子，老师布置了一些CGAL基础操作的任务，进行练习。感觉国内这部分的介绍较少。这里做一点小的贡献吧。
Voronoi需要你先了解狄洛尼三角剖分。在cgal中Voronoi图是通过狄洛尼三角形求对偶得到的。

环境以及版本

xcode
cgal 11

代码

#include 
#include 
#include 
#include 
#include 
#include 
typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
typedef CGAL::Delaunay_triangulation_2 Delaunay;
typedef Delaunay::Vertex_handle Vertex_handle;
//初始化定义相关的结构体
typedef K::Point_2 Point;
std::vector vertices;
//定义顶点的结构
int global_w, global_h;
void points_add_point( int x, int y )
{
    vertices.push_back( Point( x, global_h-y ) );
}
void points_draw()
{
    glClear(GL_COLOR_BUFFER_BIT);
    glPushMatrix();
    std::vector ::iterator iter;
    glColor3f( 0.0, 1.0, 1.0 );
    glPointSize(5);
    glBegin(GL_POINTS);
    for( iter = vertices.begin(); iter != vertices.end(); iter++ )
        glVertex2i( iter->hx(), iter->hy() );
    glEnd();
    glPopMatrix();
    glutSwapBuffers();
}
void points_triangulation()
{
    points_draw();                          //最后一个点还要再画一下！
    Delaunay dt;
    dt.insert(vertices.begin(), vertices.end());
    //将vector数组传入狄洛尼三角形数据结构
    //cgal提供狄洛尼三角形的核心数据结构就是Delaunay
    glPushMatrix();
    Delaunay::Finite_faces_iterator fit;
    //遍历算法生成的所有三角面（其实是三角形）
    glColor3f( 1.0, 1.0, 1.0 );
    for( fit = dt.finite_faces_begin(); fit != dt.finite_faces_end(); fit ++)
    {
        //开始绘制三角形
        glBegin(GL_LINE_LOOP);
        glVertex2i( fit->vertex(0)->point().x(), fit->vertex(0)->point().y() );
        glVertex2i( fit->vertex(1)->point().x(), fit->vertex(1)->point().y() );
        glVertex2i( fit->vertex(2)->point().x(), fit->vertex(2)->point().y() );
        glEnd();
    }

        Delaunay::Edge_iterator eit;
        //遍历Delaunay的所有边，绘制Delaunay图的对偶图，即Voronoi图
        glEnable( GL_LINE_STIPPLE );//使用点画模式，即使用虚线来绘制Voronoi图
        glLineStipple( 1, 0x3333 );
        glColor3f( 0.0, 1.0,1.0 );
        for( eit = dt.edges_begin(); eit != dt.edges_end(); eit ++)
        {
            CGAL::Object o = dt.dual(eit);
            //在其对偶图中所对应的边
            if (CGAL::object_cast(&o)) //如果这条边是线段，则绘制线段
            {
                glBegin(GL_LINES);
                glVertex2i( CGAL::object_cast(&o)->source().hx(), CGAL::object_cast(&o)->source().hy() );
                glVertex2i( CGAL::object_cast(&o)->target().hx(), CGAL::object_cast(&o)->target().hy() );
                glEnd();
            }
            else if (CGAL::object_cast(&o))//如果这条边是射线，则绘制射线
            {
                glBegin(GL_LINES);
                glVertex2i( CGAL::object_cast(&o)->source().hx(), CGAL::object_cast(&o)->source().hy() );
                glVertex2i( CGAL::object_cast(&o)->point(1).hx(), CGAL::object_cast(&o)->point(1).hy() );
                glEnd();
            }
        }
        glDisable( GL_LINE_STIPPLE );//关闭点画模式
    glPopMatrix();
    glutSwapBuffers();
}
void display(void)
{}
void init(void)
{
    //初始化绘制环境
    glClearColor (0.0, 0.0, 0.0, 0.0);
    glShadeModel (GL_FLAT);
}
void reshape(int w, int h)
{
    global_w = w;
    global_h = h;
    glViewport (0, 0, w, h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0, w, 0, h, -1.0, 1.0);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}
void mouse(int button, int state, int x, int y)
{   //定义鼠标事件
    if ( button == GLUT_LEFT_BUTTON && state == GLUT_UP )
    {
        points_add_point(x,y);
        points_draw();
    }
    if ( button == GLUT_RIGHT_BUTTON && state == GLUT_UP )
        points_triangulation();
}
void read_file()//从文件中读入点集数据，调试时所使用
{
    //文件读取
    FILE* f;
    f = freopen( "data.txt", "r", stdin );

    int a,b;
    while(std::cin>>a >> b)
    {
        vertices.push_back( Point( a, b ) );
    }
    fclose(f);
}
int main(int argc, char** argv)
{
    //初始化配置环境
    glutInit(&argc, argv);
    glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB);
    glutInitWindowSize (800, 600);
    glutInitWindowPosition (100, 100);
    glutCreateWindow ("Delaunay+Voronoi");
    init ();
    glutDisplayFunc(display);
    glutReshapeFunc(reshape);
    glutMouseFunc(mouse);
    glutMainLoop();
    return 0;
}