2D Sine Wave Example Using PyOpenGL

Here is an example of a moving 2D sine wave using Python 3, PyGame, and PyOpenGL.  See a https://blog.gahooa.com/2018/02/11/pygame-and-opengl-on-windows-10/  for how to install them.

sine

This sample program is designed to have a 100×60 unit working area with a 10 unit buffer around the edges.  You can see the axis in the lower-left (0,0) where Y+ is up, and X+ is to the right.

The structure of the program was created to make it super easy to work on the “guts” of the graphics without getting it confused with the “bookkeeping” end of OpenGL or PyGame.

Note: the glOrtho() command is how 2D “parallel perspective” is setup.  It defines the left, right, bottom, top, near plane, and far plane.  Because it is parallel, there is not the notion of a “camera” per-se, but rather section of the plane that should be viewed.  Documented here:

https://www.khronos.org/registry/OpenGL-Refpages/gl2.1/xhtml/glOrtho.xml

Here is the code!

#!/usr/bin/env python
###############################################################################
# Action Happens Here 50 times per second
def tick(i):
#glRotatef(1, 0, 0, 1)
#glTranslatef(0, 0, 1)
# Draw Axis
axis(i)
# Draw sinewave
for x in range(200):
x = x/2.0
y = math.sin(math.radians(x+i) * 10) * 30 + 30
cquad((x,y,0), 1, (y/60.0,0,x/100.0)) #(center, diameter, color)
###############################################################################
# The rest of this is the bones that make it work
import time
import pygame
from pygame.locals import *
from OpenGL.GL import *
from OpenGL.GLU import *
from OpenGL.arrays import vbo
import math
FPS_TARGET = 50
def axis(i):
glBegin(GL_LINES)
#x = red
#y = green
#z = blue
glColor3f(1, 0, 0)
glVertex3fv((0, 0, 0))
glVertex3fv((1, 0, 0))
glColor3f(0, 1, 0)
glVertex3fv((0, 0, 0))
glVertex3fv((0, 1, 0))
glColor3f(0, 0, 1)
glVertex3fv((0, 0, 0))
glVertex3fv((0, 0, 1))
glEnd()
def quad(points, color):
glBegin(GL_QUADS)
glColor3f(*color)
for p in points:
glVertex3fv(p)
glEnd()
def cquad(point, size, color):
glBegin(GL_QUADS)
glColor3f(*color)
x,y,z = point
s = size/2.0
glVertex3fv((xs,ys,z))
glVertex3fv((x+s,ys,z))
glVertex3fv((x+s,y+s,z))
glVertex3fv((xs,y+s,z))
glEnd()
def main():
#initialize pygame and setup an opengl display
pygame.init()
pygame.display.set_mode((1200,800), OPENGL|DOUBLEBUF)
glEnable(GL_DEPTH_TEST) #use our zbuffer
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
#setup the camera
glMatrixMode(GL_PROJECTION)
#gluPerspective(45.0,1000/1000,0.1,1000.0) #setup lens
#glOrtho(-10,10,-10,10,1,20)
glOrtho(10,110,10,70,1,1)
#glTranslatef(0, 0, -100) #move back
#glRotatef(-20, 1, 0, 0) #orbit higher
nt = int(time.time() * 1000)
for i in range(2**63):
nt += 1000//FPS_TARGET
#check for quit'n events
event = pygame.event.poll()
if event.type == QUIT or (event.type == KEYDOWN and event.key == K_ESCAPE):
break
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT)
tick(i)
pygame.display.flip()
ct = int(time.time() * 1000)
pygame.time.wait(max(1,nt ct))
if i % FPS_TARGET == 0:
print(ntct)
if __name__ == '__main__': main()

view raw
sinewave.py
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