RE: [pygame] Why does my ball vibrate?

[Boer Kees <mstrblstrprdctns@xxxxxxxxxxx>]

#ok, I think I have it broken down into pieces now... check out this code:
#---- 
import sys, pygame, math
pygame.init()
pixelspercm=10.0
gravity=9.80 * 10.0 # meter per second per second (juiced up a little :) )
framerate=50.0 # per second
lossperbounce=0.33 # lose energy per bounce
framestosilence=3#if a bounce occurs AGAIN within the next 3 frames, consider the ball dead
 
class Ball(object):
    def __init__(self, id,pos=(0,0)):
        self.speed=0.0 # meter per second
        self.diameter=0.025 # meter
        self.pos=pos
        self.previous=0#count how many frames ago we had the previous bounce
        self.name=id#just some name to show for feedback
        image=pygame.Surface((int(self.diameter*2*pixelspercm*100),int(self.diameter*2*pixelspercm*100)))
        image.set_colorkey((0,0,0))
        image.fill((0,0,0))
        pygame.draw.circle(image, (255,255,255), (int(self.diameter*pixelspercm*100),int(self.diameter*pixelspercm*100)), int(self.diameter*pixelspercm*100))
        self.image=image
    def updatepos(self,ms):
        if not (self.speed==0 and self.pos[1]==300):
            distance=self.DeltaX2(self.speed, gravity,ms/1000.0)
            if distance+self.pos[1]<300:
                self.speed=self.FinalVelocity1(self.speed,gravity,ms/1000.0)
                self.pos=(self.pos[0],distance+self.pos[1])
                if self.previous>0:
                    self.previous=self.previous-1
                    print self.name, 'normal cycle',self.previous
            else:
                print self.name
                dis2=300-self.pos[1]# distance to ground
                print 'distance to ground=',dis2
                ms2=self.MsTillGround(dis2,self.speed,self.FinalVelocity1(self.speed,gravity,ms/1000.0)) #ms till ground
                print 'ms till ground=',ms2
                endvel=self.FinalVelocity1(self.speed, gravity, (ms-ms2)/1000.0)#speed at ground
                speedatground=-endvel*(1-lossperbounce)#lose energy
                print 'speed at ground=',speedatground
                dis3=self.DeltaX2(speedatground, gravity,(ms-ms2)/1000.0)#deltaX after all ms
                print 'deltaX after all ms=',dis3
                endvel2=self.FinalVelocity1(speedatground, gravity, (ms-ms2)/1000.0)#speed after time
                print 'speed after time=',endvel2
                if self.previous>1:
                    self.pos=(self.pos[0],300)
                    self.speed=0.0
                    print 'self.speed=',self.speed
                    print 'self.pos=',self.pos
                    print 'SILENCE!'
                else:
                    self.speed=endvel2
                    self.pos=(self.pos[0],300+dis3)
                    print 'self.speed=',self.speed
                    print 'self.pos=',self.pos
                self.previous=framestosilence
 
    def MsTillGround(self, Dx, Vi, Vf):
        #Dx=1/2*(Vi+Vf)*t
        #t=Dx/(1/2*(Vi+Vf))
        t=Dx/(0.5*(Vi+Vf))
        return t*1000.0 # t is in seconds, but we want the amount of milliseconds
       
    def FinalVelocity1(self,Vi,A,t):
        # ### 1
        # Vf=Vi+A*t           
        # Final Velocity = Initial Velocity + Acceleration * time
        # meter/second = meter/second + meter/second/second * second
        return Vi+A*t
   
    def AverageVelocity(self,Vi,Vf):   
        # ### 2
        # Va=(Vi+Vf)/2
        # Average Velocity = ( Initial Velocity + Final Velocity )/2
        # meter/second = ( meter/second + meter/second )/2
        return (Vi+Vf)/2
   
    def DeltaX1(self,Vi,Vf,t):   
        # ### 3
        # Dx=1/2*(Vi+Vf)*t
        # DeltaX = 1/2 * ( Initial Velocity + Final Velocity ) * time
        # meter = 1/2 * ( meter/second + meter/second )* second
        return 0.5*(Vi+Vf)*t
   
    def DeltaX2(self,Vi,A,t):   
        # ### 4
        # Dx=Vi*t+ 1/2*a* t^2 # notice: t^2 in python is: t**2
        # DeltaX = Initial Velocity * time+1/2*Acceleration* time*time
        # meter = meter/second * second+1/2*meter/second/second * second*second
        return Vi*t+0.5*A*t**2
   
    def FinalVelocity2(self,Vi,A,Dx):   
        # ### 5
        # Vf^2=Vi^2+2*a*Dx
        # Final Velocity^2=Initial Velocity^2+2*Acceleration*DeltaX
        # meter/second*meter/second= meter/second*meter/second+2*meter/second/second*meter
        Vf2=Vi**2+2*A*Dx   
        return math.sqrt(Vf2)
 
screen = pygame.display.set_mode((200, 400), 0, 32)
balls = []
balls.append(Ball('Ball 1',(78,15)))
balls.append(Ball('Ball 2',(12,158)))
balls.append(Ball('Ball 3',(122,56)))
newtime=oldtime=0
while True:
    newtime=pygame.time.get_ticks() # milliseconds since start of program
    if newtime-oldtime>(1000.0/framerate)*2:
        print 'LAGGING!'
    if newtime-oldtime>1000.0/framerate:
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                exit()
        screen.fill((0, 0, 0))
        for ball in balls:
            ball.updatepos(newtime-oldtime)
        for ball in balls:
            screen.blit(ball.image, ball.pos)
        pygame.draw.line(screen, (255,255,255), (0,350), (200,350), 1)
        pygame.display.update()
        oldtime=newtime
#----

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