Bouncing inside Cylinder

from visual import *
from random import uniform

display(center=(0,2,0),background=(1,1,1), autoscale=False, range=4.5,        
        width=600, height=600,  forward=(-.4,-.3,-1)) #arah kamera

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

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      = 0
bola.x      = 0
bola.z      = 1

v           = vector(2,0,0)
dt          = 1./16
r           = bola.pos
rc          = silinder.radius

def pantul():
    global r,v
    if mag(r)>=rc:
        r   = 1.9*norm(r)
        vp  = (dot(v,norm(r)))*norm(r)
        vr  = v-vp
        v   = vr - vp

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

    bola.pos  = r

    pantul()

while 1:
    rate(7)
    proses()

.

Dot Product

Steller

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()

.

N-Spring System

 Using Visual Python

 I like the result, :)

#code
from visual import *

n       = 13
display(center=(n/2,0,0),background=(1,1,1), autoscale=False, range=(7),        
        width=600, height=600,  forward=(-.4,-.3,-1)) #arah kamera

distant_light(direction=(1,1,1), color=color.orange)
dt      = 1./8.
dx      = []
k       = []
m       = []
l0      = []
l       = []
v       = []
x       = []
for i in arange(n):
    dx.append(.1)
    k.append(1.)
    m.append(1.)
    l0.append(1.)
    l.append(1.)
    v.append(0.)
    x.append(0.)
pegas   = []
kotak   = []

for i in arange(n):
    spring  = helix(pos=(0,0,0), axis=(5,0,0), radius=0.2, color=color.red, length=1.)
    pegas.append(spring)
    ko      =  box(pos=(0,0,0), width=.5, height=.5, length= .5, color= color.green)
    kotak.append(ko)

box(pos=(-1,.64,0), width=n, height=2, length= 2, color=color.black)
box(pos=(n/2.,-.36,0), width=n, height=.2, length= n, color=color.white,opacity=.9)

#usikan
l[0]        = 1.2 
l[n-1]      = .9
#posisi x
position    = 0
for i in arange(n):
    position    +=l[i]
    x[i]        = position
    kotak[i].x  = x[i]


def updatePegas():
    global l
    for i in arange(n):
        if i!=0:
            pegas[i].x  = x[i-1]
            l[i]        = x[i]-x[i-1]
        else:
            l[i]        = x[i]

        kotak[i].x      = x[i]
        pegas[i].length = l[i]
        
def proses():
    for i in arange(n):
        dx[i]   = l[i]-l0[i]
        f0      = -k[i]*dx[i]
        if i<n-1:
            dx[i+1] = l[i+1]-l0[i+1]
            f1      = -k[i+1]*dx[i+1]
            a       = (f0-f1)/m[i]
        else:
            a       = f0/m[i]
        v[i]    += a*dt
        x[i]    += v[i]*dt
    updatePegas()
while 1:
    rate (19)
    proses()

.

Here's the Culprit

 In Visual Python, helix object will generate error if helix.length = some array like the code below. I use dl, an array, for the length value

from visual import *

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

distant_light(direction=(1,1,1), color=color.red)
n       = 1
dt      = 1./8.
dl      = ones(1)

pegas   = []

print dl


for i in arange(n):
    spring  = helix(pos=(0,0,0), axis=(5,0,0), radius=0.2, color=color.red, length=1.)
    pegas.append(spring)

def updatePegas(l):
    pegas[0].length = l
    
    

def proses():
    global dl
    l   = pegas[0].length
    if l>2:
        l   = 2
        dl[0]  *= -1
    elif l<.5:
        l   = .5
        dl[0]  *= -1
    l   += dl[0]
    updatePegas(l)
    
while 1:
    rate (19)
    proses()

    
    
    
    

    

.



And the result is

Traceback (most recent call last):
  File "springList.py", line 40, in 
    proses()
  File "springList.py", line 36, in proses
    updatePegas(l)
  File "springList.py", line 22, in updatePegas
    pegas[0].length = l
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/VPython-6.11-py2.7-macosx-10.6-intel.egg/visual_common/primitives.py", line 850, in set_length
    self.__frame.axis = self.__axis.norm()
AttributeError: 'numpy.ndarray' object has no attribute 'norm'

If we change dl from array to list, like the code below, everything is suddenly OK, :)

from visual import *

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

distant_light(direction=(1,1,1), color=color.red)
n       = 1
dt      = 1./8.
#dl      = ones(1)
dl      = []
dl.append(.1)
pegas   = []

print dl


for i in arange(n):
    spring  = helix(pos=(0,0,0), axis=(5,0,0), radius=0.2, color=color.red, length=1.)
    pegas.append(spring)

def updatePegas(l):
    pegas[0].length = l
    
    

def proses():
    global dl
    l   = pegas[0].length
    if l>2:
        l   = 2
        dl[0]  *= -1
    elif l<.5:
        l   = .5
        dl[0]  *= -1
    l   += dl[0]
    updatePegas(l)
    
while 1:
    rate (19)
    proses()

    
    
    
    

    

.

Gonna rewrite the code.

Double Spring System

Akhirnya.

With Visual Python module

I couldn't use list for spring length since it'll trigger some error for helix object. It's very unfortunate because it would come handy as we expand the number of spring and mass.

Anyway, here's the code

#code
from visual import *
from random import uniform,random
from visual.controls import *

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

distant_light(direction=(1,1,1), color=color.red)
n       = 2
dt      = 1./8.
pegas   = []
kotak   = []
box(pos=(-1,0,0), width=2, height=2, length= 2, color=color.black)
box(pos=(0,-.36,0), width=2, height=.2, length= 5, color=color.black,opacity=.3)
for i in arange(n):
    spring  = helix(pos=(0,0,0), axis=(5,0,0), radius=0.2, color=color.red, length=1.)
    pegas.append(spring)
    ko      = box(pos=(0,0,0), width=.5, height=.5, length= .5, color= color.green)
    kotak.append(ko)

k0      = 1.
k1      = 1.

m0      = 1.
m1      = 1.

l00     = 1.
l01     = 1.

l0      = 1.
l1      = 1.1

x0      = l0
x1      = l0+l1

v0      = 0.
v1      = 0.


y = 1.
print x1
def updatePegas():
    global x0,x1
    kotak[0].x      = x0
    pegas[0].length = l0
    
    kotak[1].x      = x1
    pegas[1].x      = l0
    pegas[1].length = l1

    

def proses():
    global l0,v0,x0,l1,v1,x1
    #untuk m0
    dx0     = l0-l00
    f0     = -k0*dx0
    dx1     = l1-l01
    f1     = -k1*dx1
    a0      = (f0-f1)/m0
    v0      += a0*dt
    x0      += v0*dt
    l0      = x0
    #untuk m1
    a1      = f1/m1
    v1      += a1*dt
    x1      += v1*dt
    l1      = x1-x0
    
    
    updatePegas()
    
while 1:
    rate (39)
    y   += .1
    proses()

    
    
    
    

    

.