mismatch between display and position value of objects

[Haim Edri]

Hi

I wrote this small exercise for my students (to eventually create MD simulation).

I found it strange that the last ball at the last second does not align with the others, although it's position is seem to be correct (when printed it  looks right) 

I noticed that even if I try to update one of the ball's position outside the loops (at the end of the code) - the value changes but the animation don't.

whould love to get help..

The code: 

from visual import *

table = box(size=(11,11,0))

x=[]

i=-5

while i <= 5:

    ball = sphere(pos = (i,-5,0) ,radius = 0.4, color=color.red)

    x.append(ball)

    i=i+1

t=0

while t < 2:

   

    i=0

    while i<=10:

        rate(10)

        x[i].pos.y = x[i].pos.y+1.0

        print(i,x[i].pos.y)

        i = i + 1

     

    t=t+1

[Steve Spicklemire]

Hi Haim,

When I run your code, I see no terrible misalignment. Is it very subtle? What platform/version of VPython are you running?

thanks,

-steve

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[Haim Edri]

I use Idle, and when I run the code, I get:

but when I print  the position, the last ball has the same position as the rest of the balls (x[10].pos.y=-3)

[Steve Spicklemire]

Sounds like you need one more call to “rate(10)” although usually, after your program exits, VPython drops into an ‘exit’ routine that calls the rate() function repeatedly. It *sounds* like that’s not happening for you somehow. What version?

thanks,
-steve

> On Jan 15, 2017, at 6:04 AM, Haim Edri <edri....@gmail.com> wrote:
>
> I use Idle, and when I run the code, I get:
>
>
>

[Haim Edri]

I tried to add another rate(10) - it didn't help.

I also noticed that if i write another line after the loops end that update the position - the animation ignores it, although it is stored in the shapes attribute.

my python (and idle) version is 2.7.9 

any ideas?

[Steve Spicklemire]

Hi Edri,

Can you send your new code with the added rate() call?

Also, what happens when you type:

>>> import visual
>>> visual.version
('6.11', 'release')
>>>

into the VIDLE shell?

thanks,
-steve

[Bruce Sherwood]

The problem is that you are using IDLE. You need to use VIDLE, which is part of the Classic VPython installation.

[Haim Edri]

problem solved - it works just fine with VIDLE!!

Thanks!