三维坐标系下 使用opengl拾取物件的操作【新浪博客迁移】

代码来自nehe opengl：
void select()
{
 

   GLuintbuffer[512];
    GLuinthits;
    GLintviewPort[4];

   glGetIntegerv(GL_VIEWPORT,viewPort);
   glSelectBuffer(512,buffer);

    (void)glRenderMode(GL_SELECT);

   glInitNames();
   glPushName(0);

   glMatrixMode(GL_PROJECTION);
   glPushMatrix();
   glLoadIdentity();


   gluPickMatrix((GLdouble)lmouseX,(GLdouble)(viewPort[3]- lmouseY),1.0,1.0,viewPort);

   gluPerspective(45.0f,(GLfloat)(viewPort[2]-viewPort[0])/(GLfloat)(viewPort[3]- viewPort[1]),0.1f,50000.0f);

   glMatrixMode(GL_MODELVIEW);

   glPushMatrix();
   glLoadIdentity();

   //矩阵变换函数
    //绘制函数
    //
   glPopMatrix();

   glMatrixMode(GL_PROJECTION);
   glPopMatrix();
   glMatrixMode(GL_MODELVIEW);
    hits =glRenderMode(GL_RENDER);
    if(hits>0)
   {      
      int   choose =buffer[3];                           // Make Our Selection The First Object
      int depth =buffer[1];                           // Store How Far Away It Is

      for (int loop = 1; loop <(int)hits; loop++)               // Loop Through All The Detected Hits
      {
         // If This Object Is Closer To Us Than The One WeHave Selected
         if (buffer[loop*4+1] <GLuint(depth))
         {
            choose =buffer[loop*4+3];                  // Select The Closer Object
            depth =buffer[loop*4+1];                  // Store How Far Away It Is
         }      
      }
      int k = 0;
    }
    
}

1.插入相应的矩阵变换函数 矩阵变换函数相当重要 如果错误将会影响整个操作的执行
2.在绘制函数中有glloadname函数，注意glloadname函数不能放在glbegin和glend之间