func gluPerspective(fovy float64, aspect float64, zNear float64, zFar float64) {
gl.MatrixMode(gl.PROJECTION)
gl.LoadIdentity()
ymax := zNear * math.Tan(fovy*math.Pi/360)
ymin := -ymax
xmin := ymin * aspect
xmax := ymax * aspect
gl.Frustum(xmin, xmax, ymin, ymax, zNear, zFar)
}
func setupGL() {
gl.ShadeModel(gl.FLAT)
gl.ClearColor(0.75, 0.75, 0.75, 1.0)
gl.Enable(gl.DEPTH_TEST)
gl.LineWidth(1)
gl.Viewport(0, 0, winWidth, winHeight)
gl.Hint(gl.PERSPECTIVE_CORRECTION_HINT, gl.NICEST)
gluPerspective(45, float64(winWidth)/winHeight, 10, 1000)
gl.MatrixMode(gl.MODELVIEW)
gl.LoadIdentity()
}