# PyPolar.py
# Plotting Polar Equations

from OpenGL.GL import *
from OpenGL.GLU import *
from OpenGL.GLUT import *
from numpy import *
import sys

#  Set the width and height of the window with global variables
#  Set the axis range globally using global variable axrng
global width
global height
global axrng

#  Initial values
width = 400
height = 400
axrng = 7.0
				
def init():
	glClearColor(1.0, 1.0, 1.0, 1.0)

# GLUT Display Function
def plotpolar():
	glClear(GL_COLOR_BUFFER_BIT)
	
	# Plot axis lines for reference
	glColor3f(0.0, 0.0, 0.0)
	glBegin(GL_LINES)
	glVertex2f(-axrng,0)
	glVertex2f(axrng,0)
	glVertex2f(0,axrng)
	glVertex2f(0,-axrng)
	glEnd()
	
	# Plot polar equation for a Limacon
	glPointSize(2.0)
	glBegin(GL_POINTS)
	for theta in arange(0.0, 6.28, 0.001):
		r = 4*cos(theta) + 2
		x = r*cos(theta)
		y = r*sin(theta)
		glVertex2f(x,y)
	glEnd()
	glFlush()

# This is new... this is a reshape function so that the
# aspect ratio of the graphics window will be preserved
# and anything we draw will look in proper proportion
def reshape(w, h):
	
	# To insure we don't have a zero window height
	if h==0:
		h = 1
	
	#  Fill the entire graphics window!
	glViewport(0, 0, w, h)
	
	#  Set the projection matrix... our "view"
	glMatrixMode(GL_PROJECTION)
	glLoadIdentity()
	
	#  Set the aspect ratio of the plot so that it
	#  Always looks "OK" and never distorted.
	if w <= h:
		gluOrtho2D(-axrng, axrng, -axrng*h/w, axrng*h/w)
	else:
		gluOrtho2D(-axrng*w/h, axrng*w/h, -axrng, axrng)
	
	#  Set the matrix for the object we are drawing
	glMatrixMode(GL_MODELVIEW)
	glLoadIdentity()
	
def keyboard(key, x, y):
	#  Allows us to quit by pressing 'Esc' or 'q'
	if key == chr(27) or key == "q":
		sys.exit()

def main():
	global width
	global height
	
	glutInit(sys.argv)
	glutInitDisplayMode(GLUT_RGB|GLUT_SINGLE)
	glutInitWindowPosition(10,10)
	glutInitWindowSize(width,height)
	glutCreateWindow("Polar Equations")
	glutReshapeFunc(reshape)
	glutDisplayFunc(plotpolar)
	glutKeyboardFunc(keyboard)
	
	init()	
	
	glutMainLoop()

main()

# End Program