python使用opengl绘制竹叶的十字型

#coding=utf-8

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

def init():
glClearColor(1.0, 1.0, 1.0, 1.0)
gluOrtho2D(-5.0, 5.0, -5.0, 5.0)

#竹叶的十字型，注意是巧用y=x**2和y=math.sqrt(x)两个函数
def plotfunc():
glClear(GL_COLOR_BUFFER_BIT)
glColor3f(0.0, 0.0, 0.0)
glPointSize(1.0)
glBegin(GL_LINES)
glVertex2f(-5.0, 0.0)
glVertex2f(5.0, 0.0)
glVertex2f(0.0, 5.0)
glVertex2f(0.0, -5.0)
glEnd()
x = 0.0
while x <= 1.0:
y = x**2
glBegin(GL_POINTS)
glVertex2f(x, y)
glVertex2f(-x, y)
glVertex2f(x, -y)
glVertex2f(-x, -y)
glEnd()
x += 0.01
x = 0.0
while x <= 1.0:
y = math.sqrt(x)
glBegin(GL_POINTS)
glVertex2f(x, y)
glVertex2f(-x, y)
glVertex2f(x, -y)
glVertex2f(-x, -y)
glEnd()
x += 0.01
glFlush()

def main():
glutInit(sys.argv)
glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB)
glutInitWindowSize(500, 500)
glutInitWindowPosition(100, 100)
glutCreateWindow("Function plotter")
glutDisplayFunc(plotfunc)

init()
glutMainLoop()

main()