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

seed = 1
if len(sys.argv) > 1:
	seed = int(sys.argv[1])

def generatePoints(level):
    random.seed(seed)
    numPoints = 2**level + 1
    p = [0] * numPoints
    displacement = 1.0
    for l in range(level-1, -1, -1):
        step = 2**l
        for i in range(step, numPoints, step*2):
            p[i] = (p[i-step] + p[i+step])/2.0 + random.gauss(0.0, displacement)
        displacement /= 2.5
    return p

level = 0

def draw():
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
    
    glMatrixMode(GL_PROJECTION)
    glLoadIdentity()
    gluOrtho2D(-0.5, 1.5, -2.0, 2.0)
    glMatrixMode(GL_MODELVIEW)

    glLoadIdentity()
    
    points = generatePoints(level)
    glBegin(GL_LINE_STRIP)
    i = 0
    for p in points:
        glVertex2f(i/(len(points)-1.0), p)
        i += 1
    glEnd()
    glutSwapBuffers()


def keyboard(key, x, y):
    global level
    if key == chr(27):
        sys.exit(0)
    elif key == '+':
        level += 1
    elif key == '-' and level > 0:
        level -= 1
    glutPostRedisplay()

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