import sys, Image
from OpenGL.GL import *
from OpenGL.GLU import *
from OpenGL.GLUT import *

viewRotZ = 0
viewRotX = 0

import random

def makeHeightField(level):
	size = 2**level + 1
	h = [[0]*size for _ in range(0,size)]
	displacement = 4.0
	for l in range(level-1, -1, -1):
		step = 2**l
		for i in range(0, size, step*2):
			for j in range(step, size, step*2):
				h[i][j] = (h[i][j-step]+h[i][j+step])/2.0 + random.gauss(0,displacement)
		for i in range(step, size, step*2):
			for j in range(0, size, step*2):
				h[i][j] = (h[i-step][j]+h[i+step][j])/2.0 + random.gauss(0,displacement)
		for i in range(step, size, step*2):
			for j in range(step, size, step*2):
				h[i][j] = (h[i-step][j]+h[i+step][j]+h[i][j-step]+h[i][j+step])/4.0 + random.gauss(0,displacement)
		displacement /= 1.8
	return h


def makeTerrain():
	hf = makeHeightField(6)
	size = len(hf)
	dl = glGenLists(1)
	glNewList(dl, GL_COMPILE)
	glTranslatef(-size/2.0, -size/2.0, 0)
	glPolygonMode(GL_FRONT_AND_BACK, GL_LINE)
	for i in range(0,size-1):
		glBegin(GL_TRIANGLE_STRIP)
		for j in range(0,size):
			glVertex3f(i,j,hf[i][j])
			glVertex3f(i+1,j,hf[i+1][j])
		glEnd()
	glEndList()
	return dl

def draw():
    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, -30.0)
    glRotatef(viewRotX, 1.0, 0.0, 0.0)
    glRotatef(viewRotZ, 0.0, 0.0, 1.0)
    
    glCallList(terrain)
    glutSwapBuffers()


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

def specialkey(key,x,y):
    global viewRotX, viewRotZ
    if key == GLUT_KEY_LEFT:
        viewRotZ = viewRotZ + 3
    elif key == GLUT_KEY_RIGHT:
        viewRotZ = viewRotZ - 3
    elif key == GLUT_KEY_UP:
        viewRotX = viewRotX + 3
    elif key == GLUT_KEY_DOWN:
        viewRotX = viewRotX - 3
    glutPostRedisplay()

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