正方形的叠加

#include <GL/glut.h>
void myDisplay(void)

{
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glClear(GL_COLOR_BUFFER_BIT);

    glBegin(GL_POLYGON);
    glVertex2f(-0.5, 0.5);
    glVertex2f(0.5, 0.5);
    glVertex2f(0.5, -0.5);
    glVertex2f(-0.5, -0.5);
    glEnd();

    glBegin(GL_POLYGON);
    glColor3f(1, 0, 0);
    glVertex2f(0, 0.5);
    glVertex2f(0.5, 0);
    glVertex2f(0, -0.5);
    glVertex2f(-0.5, 0);
    glEnd();

    glBegin(GL_TRIANGLES);
    glColor3f(0, 0, 1);
    glVertex2f(0, 1);
    glVertex2f(-0.5, 0.5);
    glVertex2f(0.5, 0.5);
    glEnd();

    glBegin(GL_TRIANGLES);
    glColor3f(1, 1, 0);
    glVertex2f(1, 0);
    glVertex2f(0.5, 0.5);
    glVertex2f(0.5, -0.5);
    glEnd();

    glBegin(GL_TRIANGLES);
    glColor3f(0, 1, 0);
    glVertex2f(0, -1);
    glVertex2f(-0.5, -0.5);
    glVertex2f(0.5, -0.5);
    glEnd();

    glBegin(GL_TRIANGLES);
    glColor3f(1, 0, 1);
    glVertex2f(-1, 0);
    glVertex2f(-0.5, 0.5);
    glVertex2f(-0.5, -0.5);
    glEnd();
    glFlush();
}

int main(int argc, char *argv[])
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);
    glutInitWindowPosition(100, 100);
    glutInitWindowSize(400, 400);
    glutCreateWindow("Hello Opengl!");
    glutDisplayFunc(&myDisplay);
    glutMainLoop();
    return 0;
}