大神帮忙看一下程序看不到图像

#include<windows.h>
#include<gl/glut.h>
#include<gl/gl.h>
#include<gl/glu.h>
void RenderScene(void)
{
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(100.0f, 0.0f, 0.0f);
glRectf(100.0f, 150.0f, 150.0f, 100.0f);
glFlush();
}
void ChangeSize(GLsizei w, GLsizei h)
{
if (h == 0) h = 1;
glViewport(0, 0, w, h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
if (w <= h)
glOrtho(0.0f, 250.0f, 0.0f, 250.0f*h / w, 1.0f, -1.0f);
else
glOrtho(0.0f, 250.0f*w / h, 0.0f, 250.0f, 1.0f, -1.0f);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
void SetupRC(void)
{
glClearColor(1.0f, 1.0f, 1.0f,1.0f);
}
void main(void)
{
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutCreateWindow("GLRect");
glutDisplayFunc(RenderScene);
glutReshapeFunc(ChangeSize);
SetupRC();
glutMainLoop();
}