opengl select

#include <windows.h> 
#include <gl/gl.h> 
#include <gl/glu.h> 
#include <gl/glut.h> 
#include <stdio.h>
#include <math.h> 
#define PICK_SIZE  32
int winWidth = 400, winHeight = 300;
void Initial(void)
{
    glClearColor(1.0f, 1.0f, 1.0f, 1.0f); 
}
void DrawRect(GLenum mode)
{
    if(mode == GL_SELECT) glPushName(1); //压入堆栈
    glColor3f(1.0f,0.0f,0.0f);
    glRectf(60.0f,50.0f,150.0f,150.0f);

    if(mode == GL_SELECT) glPushName(2); //压入堆栈
    glColor3f(0.0f,1.0f,0.0f);
    glRectf(230.0f,50.0f,330.0f,150.0f);
    if(mode == GL_SELECT) glPushName(3); //压入堆栈
    glColor3f(0.0f,0.0f,1.0f);
    glRectf(140.0f,140.0f,240.0f,240.0f);
}
void ProcessPicks(GLint nPicks, GLuint pickBuffer[])
{
    GLint i;
    GLuint name, *ptr;
    printf("选中的数目为%d个\n",nPicks);
    ptr=pickBuffer;
    for(i=0;i < nPicks;i++){
        name=*ptr; //选中图元在堆栈中的位置
        ptr+=3; //跳过名字和深度信息
        ptr+=name-1; //根据位置信息获得选中的图元名字
        if(*ptr==1) printf("你选择了红色图元\n");
        if(*ptr==2) printf("你选择了绿色图元\n");
        if(*ptr==3) printf("你选择了蓝色图元\n");
        ptr++;
    }
    printf("\n\n");
}

void ChangeSize(int w, int h)
{
    winWidth = w;
    winHeight = h;
    glViewport(0, 0, w, h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(0.0,winWidth,0.0,winHeight);
}
void Display(void)
{
    glClear(GL_COLOR_BUFFER_BIT);
    DrawRect(GL_RENDER);
    glFlush();
}
void MousePlot(GLint button, GLint action, GLint xMouse, GLint yMouse)
{
    GLuint pickBuffer[PICK_SIZE];
    GLint nPicks, vp[4];
    if(button == GLUT_LEFT_BUTTON && action == GLUT_DOWN)
    {
        glSelectBuffer(PICK_SIZE,pickBuffer); //设置选择缓冲区
        glRenderMode(GL_SELECT); //激活选择模式
        glInitNames(); //初始化名字堆栈
        glMatrixMode(GL_PROJECTION);
        glPushMatrix();
        glLoadIdentity();
        glGetIntegerv(GL_VIEWPORT, vp);
        //定义一个10×10的选择区域
        gluPickMatrix((GLdouble)(xMouse), (GLdouble)(vp[3]-yMouse),10.0,10.0,vp);

        gluOrtho2D(0.0,winWidth,0.0,winHeight);
        DrawRect(GL_SELECT);
        //恢复投影变换
        glMatrixMode(GL_PROJECTION);
        glPopMatrix();
        glFlush();
        //获得选择集并输出
        nPicks = glRenderMode(GL_RENDER);
        ProcessPicks(nPicks, pickBuffer);
        glutPostRedisplay();
    }
}
int main(int argc, char* argv[])
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB); 
    glutInitWindowSize(400,300); 
    glutInitWindowPosition(100,100); 
    glutCreateWindow("拾取操作"); 
    glutDisplayFunc(Display);
    glutReshapeFunc(ChangeSize);
    glutMouseFunc(MousePlot);
    Initial(); 
    glutMainLoop(); 
    return 0;
}