# Demonstration of perspective projection
#
import sys
import time
from OpenGL.GLUT import *
from OpenGL.GL import *
from OpenGL.GLU import *

fovy = 60.0

def draw():
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
	glMatrixMode(GL_PROJECTION)
	glLoadIdentity()
	gluPerspective(fovy, 1, 1, 100)
	glMatrixMode(GL_MODELVIEW)

	glLoadIdentity()

	glColor3f(0, 0, 1)
	glBegin(GL_QUADS)
	glVertex3f(-2, -1, -8)
	glVertex3f(1, -1, -8)
	glVertex3f(1, 1, -8)
	glVertex3f(-2, 1, -8)
	glEnd()

	glColor3f(1, 0, 0)
	glBegin(GL_TRIANGLES)
	glVertex3f(-1, -1, -5)
	glVertex3f(1, -1, -5)
	glVertex3f(0, 1, -5)
	glEnd()

	glutSwapBuffers()


def keyboard(key, x, y):
	if key == chr(27):
		sys.exit(0)

def specialKey(key, x, y):
	global fovy
	if key == GLUT_KEY_LEFT:
		fovy = fovy + 1
		print "fovy =", fovy
		glutPostRedisplay()
	elif key == GLUT_KEY_RIGHT:
		fovy = fovy - 1
		print "fovy =", fovy
		glutPostRedisplay()

glutInit(sys.argv)
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH)
glutInitWindowSize(400, 400)
glutInitWindowPosition(0,0)
glutCreateWindow(sys.argv[0])
glutDisplayFunc(draw)
glutKeyboardFunc(keyboard)
glutSpecialFunc(specialKey)
glEnable(GL_DEPTH_TEST)
glutMainLoop()