求教。。。

zhy0408

#include <GL/glut.h>

void display()
{
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        glOrtho(-2.0,2.0,-2.0,2.0,-2.0,2.0);
        glClear(GL_COLOR_BUFFER_BIT);
        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();
        gluLookAt(0.5,0.5,0.5,0,0.0,0.0,0.0,1.0,0.0);
        glutWireCube(2.0);
        glutSwapBuffers();
}

void init()
{
        glClearColor(1.0,1.0,1.0,1.0);
        glColor3f(1.0,0.0,0.0);
}

int main(int argc,char** argv)
{
         glutInit(&argc,argv);
         glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
         glutInitWindowSize(500,500);
         glutInitWindowPosition(0,0);
         glutCreateWindow("cube");
         glutDisplayFunc(display);
         init();
         glutMainLoop();
}


为什么不能看到整个立方体？？？求大神指导。。。