Pendulum

# pendulum
# joe, 03/01/2015
import appuifw as A
import graphics as G
import math

def radians(degrees):
 return degrees*math.pi/180.0
sin,cos=math.sin,math.cos

class Pend:
 def __init__(self):
  self.theta=45
  self.dtheta=0
  self.rect = (PIVOT[0]-LENGTH*cos(radians(self.theta)),PIVOT[1] + LENGTH*sin(radians(self.theta)),1,1)

 def compute(self):
  scaling = 3000.0 / (LENGTH**2)
  firstDDtheta = -sin(radians(self.theta)) * scaling
  midDtheta = self.dtheta + firstDDtheta
  midtheta = self.theta + (self.dtheta + midDtheta)/2.0
  midDDtheta = -sin(radians(midtheta))*scaling
  midDtheta = self.dtheta + (firstDDtheta + midDDtheta)/2
  midtheta = self.theta + (self.dtheta + midDtheta)/2
  midDDtheta = -sin(radians(midtheta)) * scaling
  lastDtheta = midDtheta+midDDtheta
  lasttheta = midtheta + (midDtheta + lastDtheta)/2.0
  lastDDtheta = -sin(radians(lasttheta)) * scaling
  lastDtheta = midDtheta + (midDDtheta + lastDDtheta)/2.0
  lasttheta = midtheta + (midDtheta + lastDtheta)/2.0
  self.dtheta = lastDtheta
  self.theta = lasttheta
  self.rect = (PIVOT[0]- LENGTH*sin(radians(self.theta)),PIVOT[1] + LENGTH*cos(radians(self.theta)),1,1)

 def update(self,g):
  self.compute()
  self.draw(g)

 def draw(self,x):
  cx,cy=self.rect[0] + self.rect[2]/2, self.rect[1] + self.rect[3]/2
  x.line((5,PIVOT[1],W-5,PIVOT[1]),0xffffff)
  x.line((PIVOT[0],PIVOT[1],cx,cy),0xffffff)
  x.point((PIVOT[0],PIVOT[1],5,0),0x00ff00,width=4)
  x.point((cx,cy),0x00ff00,width=SIZE)


class App:
 def __init__(self):
  self.run=0
  A.app.screen='full'
  self.c = A.Canvas(redraw_callback=self.redraw,event_callback=None)
  A.app.body=self.c
  A.app.exit_key_handler = self.stop

 def stop(self):
  self.run=0

 def redraw(self,x):
  if BG:
   self.c.blit(BG)

 def play(self):
  self.run=1
  while self.run:
   BG.clear(0)
   BG.text((5,H-8),u'Pendulum',0xffffff)
   pen.update(BG)
   self.redraw(0)
   A.e32.ao_sleep(1e-04)


W,H=G.sysinfo.display_pixels()
PIVOT=(W/2,H/8)
LENGTH,SIZE=PIVOT[1]*5,15
BG=G.Image.new((W,H))


pen=Pend()
App().play()