interpolation demo

interp.py

# interp.py
# by Dave Pape, for DMS 423
#
# Moves two squares by interpolation of their X position
# The timing used in the interpolation is different -
# the red square moves purely linearly; the blue square
# uses a slow-in-slow-out

import time
from pyglet.gl import *

window = pyglet.window.Window(500,500)

pos1 = 100
pos2 = 200
startTime = time.time()

square = pyglet.graphics.vertex_list(4, ('v2f', [-10,-10, 10,-10, -10,10, 10,10]))

@window.event
def on_draw():
    glClear(GL_COLOR_BUFFER_BIT)
    glLoadIdentity()

    glPushMatrix()
    glTranslatef(pos1,350,0)
    glColor3f(1,0,0)
    square.draw(GL_TRIANGLE_STRIP)
    glPopMatrix()

    glPushMatrix()
    glTranslatef(pos2,150,0)
    glColor3f(0,0,1)
    square.draw(GL_TRIANGLE_STRIP)
    glPopMatrix()


def lerp(start,end,a):
    return (1-a) * start + a * end

def slowInSlowOut(a):
    return -2*a*a*a + 3*a*a

def update(dt):
    global pos1, pos2, startTime
    a = (time.time() - startTime) / 5
    if a > 1:
        a = 0
        startTime = time.time()
    pos1 = lerp(100,400,a)
    pos2 = lerp(100,400,slowInSlowOut(a))


pyglet.clock.schedule_interval(update,1/60.0)
pyglet.app.run()