Bounce Over Spherical Surface

#code

from visual import *
from random import uniform


display(center=(0,2,0),background=(1,1,1), autoscale=False, range=7.5,        
        width=600, height=600,  forward=(-.4,-.3,-1)) #arah kamera

distant_light(direction=(1,1,1), color=color.red)

ball        = sphere(radius=2, color=color.red, opacity = .5)
r2          = ball.radius
silinder    = cylinder(radius=2, length=4, opacity=.3)
silinder.rotate(angle=pi/2, axis=(0,0,1),origin=(0,0,0))


bola        = sphere(color=color.green,radius=.2)
bola.y      = 3
bola.x      = uniform(-1,1)
bola.z      = uniform(-1,1)


v           = vector(0,2,0)
dt          = 1./8.
r           = bola.pos

def pantul():
    global r,v
    print v
    if mag(r)<r2:
        print mag(r)
        arah    = norm(r)
        dv      = dot(v,arah)
        v       -= dv*arah
        r       = (r2+.2)*arah
    
    

def proses():
    global r,v
    a   = vector(0,-1,0)
    v   += a*dt
    r   += v*dt

    bola.pos  = r

    pantul()

    

while 1:
    rate(11)
    proses()

.