#include <GL\glut.h>void Display(void){    glClear(GL_COLOR_BUFFER_BIT);    glLoadIdentity();    glBegin(GL_POLYGON);        glColor3f(0.0,0.0,0.0);        glVertex3f(-0.5,-0.5,-3.0);        glColor3f(1.0,0.0,0.0);        glVertex3f(0.5,-0.5,-3.0);        glColor3f(0.0,0.0,1.0);        glVertex3f(0.5,0.5,-3.0);    glEnd();    glFlush();            //Finish rendering}void Reshape(int x, int y){    if (y == 0 || x == 0) return;  //Nothing is visible then, so return    //Set a new projection matrix    glMatrixMode(GL_PROJECTION);      glLoadIdentity();    //Angle of view:40 degrees    //Near clipping plane distance: 0.5    //Far clipping plane distance: 20.0    gluPerspective(40.0,(GLdouble)x/(GLdouble)y,0.5,20.0);    glMatrixMode(GL_MODELVIEW);    glViewport(0,0,x,y);  //Use the whole window for rendering}int main (int argc, char **argv){    //Initialize GLUT    glutInit(&argc, argv);    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);    glutInitWindowSize(300,300);    //Create a window with rendering context and everything else we need    glutCreateWindow("Intro");    glClearColor(0.0,0.0,0.0,0.0);    //Assign the two used Msg-routines    glutDisplayFunc(Display);    glutReshapeFunc(Reshape);    //Let GLUT get the msgs    glutMainLoop();    return 0;}