julia.py

# PyJulia.py
# Plot a Julia set
#rebuilt GF 12sep11

from OpenGL.GL import *
from OpenGL.GLU import *
from OpenGL.GLUT import *
from numpy import *   #do we need this
import sys

# Initalize screen dimensions and the screen origin
width = 250
height = 250
hcenter = 0.0
vcenter = 0.0
axrng = 1.5
hstep = 2*axrng/width
vstep = 2*axrng/height

def init():
	# White background
	glClearColor(1.0, 1.0, 1.0, 1.0) 

	# The next statement is all one line!!!
	gluOrtho2D(hcenter-axrng,hcenter+axrng,vcenter-	axrng,vcenter+axrng)

def drawjulia():
	glClear(GL_COLOR_BUFFER_BIT)
	glBegin(GL_POINTS)
	
	# Julia set complex number
	z = complex(-0.728, 0.1230)
	
	y = vcenter + axrng
	while y > vcenter - axrng:
		y-= vstep
		x = hcenter - axrng
		while x < hcenter + axrng:
			x+= hstep
				
			n = 0
			a = complex(x,y)
			
			# n < 100 is the number of iterations
			# Increase this value to show finer detail
			# Decrease the value if nothing shows on the screen
			while n < 100:
				n+=1 
				a = a**2 + z
				zz = abs(a)

				# zz > 2 is the critical escape value
				# Some functions require larger escape values
				# This zz > 2 conditional provides coloration for 				# points outside the Julia set
				if zz > 10:
						#glColor3f(sin(2*zz),cos(zz),sin(4*zz))
						#glVertex2f(x,y)
						n = 5001
			
			# This zz < 2 conditional provides coloration for
			# points inside the Julia set.
			if zz < 10:
				glColor3f(cos(5*zz),sin(4*zz)*cos(4*zz),sin(2*zz))	
				glVertex2f(x,y)
	glEnd()
	glFlush()
			
def main():
	glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE)
	glutInitWindowPosition(50, 50)
	glutInitWindowSize(width, height)
	glutInit(sys.argv)
	glutCreateWindow("Julia Set")
	glutDisplayFunc(drawjulia)
	init()
	glutMainLoop()
	
main()

# End Program