import sys, time, math
from OpenGL.GL import *
from OpenGL.GLU import *
from OpenGL.GLUT import *

# Note: PyOpengl is missing this constant, as it only supports OpenGL 1.1.
#  As long as the OpenGL driver itself is 1.2 or later, we can just define
#  the constant ourselves, and glEnable'ing it will work.
GL_RESCALE_NORMAL = 0x803A

viewRotY = 0
viewRotX = 0
cameraVelX = 0
cameraVelY = 0
prevTime = time.time()

def draw():
	glClearColor(0, 0.3, 0.5, 0)
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
	
	glMatrixMode(GL_PROJECTION)
	glLoadIdentity()
	gluPerspective(50.0, 1.0, 1.0, 100.0)
	glMatrixMode(GL_MODELVIEW)

	glLoadIdentity()
	glTranslatef(0.0, 0.0, -15.0)
	glRotatef(viewRotX, 1.0, 0.0, 0.0)
	glRotatef(viewRotY, 0.0, 1.0, 0.0)
	
	glLightfv(GL_LIGHT0, GL_POSITION, [0, 1, 0, 0])
	glMaterialfv(GL_FRONT, GL_DIFFUSE, [0.8, 0.8, 0.8, 1])

	glPushMatrix()
	glTranslatef(-4.0, 4.0, 0.0)
	glRasterPos3f(-1, -3, 0)
	drawBitmapString("No scale")
	glutSolidSphere(2, 16, 8)
	glPopMatrix()
	
	glPushMatrix()
	glTranslatef(4.0, 4.0, 0.0)
	glRasterPos3f(-1, -3, 0)
	drawBitmapString("Scale")
	glScalef(3, 2, 1)
	glutSolidSphere(1, 16, 8)
	glPopMatrix()
	
	glEnable(GL_RESCALE_NORMAL)
	glPushMatrix()
	glTranslatef(-4.0, -2.0, 0.0)
	glRasterPos3f(-2, -3, 0)
	drawBitmapString("GL_RESCALE_NORMAL")
	glScalef(3, 2, 1)
	glutSolidSphere(1, 16, 8)
	glPopMatrix()
	glDisable(GL_RESCALE_NORMAL)
	
	glEnable(GL_NORMALIZE)
	glPushMatrix()
	glTranslatef(4.0, -2.0, 0.0)
	glRasterPos3f(-2, -3.5, 0)
	drawBitmapString("GL_NORMALIZE")
	glScalef(3, 2, 1)
	glutSolidSphere(1, 16, 8)
	glPopMatrix()
	glDisable(GL_NORMALIZE)
	
	glutSwapBuffers()


def drawBitmapString(text, font=GLUT_BITMAP_TIMES_ROMAN_24):
    for c in text:
        glutBitmapCharacter(font, ord(c))


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

def specialkey(key,x,y):
	global cameraVelX, cameraVelY
	if key == GLUT_KEY_LEFT:
	    cameraVelY += 90
	elif key == GLUT_KEY_RIGHT:
	    cameraVelY -= 90
	elif key == GLUT_KEY_UP:
	    cameraVelX += 90
	elif key == GLUT_KEY_DOWN:
	    cameraVelX -= 90

def specialkeyUp(key,x,y):
	global cameraVelX, cameraVelY
	if key == GLUT_KEY_LEFT:
	    cameraVelY -= 90
	elif key == GLUT_KEY_RIGHT:
	    cameraVelY += 90
	elif key == GLUT_KEY_UP:
	    cameraVelX -= 90
	elif key == GLUT_KEY_DOWN:
	    cameraVelX += 90

def update():
	global viewRotX, viewRotY, cameraVelX, cameraVelY
	global prevTime
	t = time.time()
	dt = t - prevTime
	prevTime = t
	viewRotX += cameraVelX * dt
	viewRotY += cameraVelY * dt
	glutPostRedisplay()

glutInit([])
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH)
glutInitWindowSize(400,400)
glutCreateWindow(sys.argv[0])
glutDisplayFunc(draw)
glutKeyboardFunc(keyboard)
glutSpecialFunc(specialkey)
glutSpecialUpFunc(specialkeyUp)
glutIgnoreKeyRepeat(1)
glutIdleFunc(update)
glEnable(GL_DEPTH_TEST)
glEnable(GL_LIGHTING)
glEnable(GL_LIGHT0)
glutMainLoop()