visualpython-users

[Visualpython-users] Generating PDF and Movies in Visual Python

[Lorenzo I. <lor...@gm...>]

Dear All,
I am a newbie in visual Python, so apologies if this is a FAQ.
I am interested in using Vpython to investigate the motion of a bunch of 
particles in space; I save the (x,y,z) coordinates of each particle as a 
function of time and I can plot easily a snapshot of the system using a 
code like:

#! /usr/bin/env python

import scipy as s
import numpy as n
import pylab as p

import visual as v

#here I do my stuff to read the configuration of the system
#and then I can finally plot a snapshot of the system at a specific time

pos_list=s.zeros(3) # I initialize the array to contain the single 
particle's coordinates

my_rad=1.06/2.

for i in xrange(0,n_part):  #n_part is the number of particles in my system
    pos_list[0]=x_list[i]  #x_list contains a list of the x-coordinate 
of all the particles in the system at a given time
    pos_list[1]=y_list[i]
    pos_list[2]=z_list[i]
    particle=v.sphere(pos=pos_list,radius=my_rad,color=v.color.blue)


and so
far so good. However, I am having a hard time in making an animation out 
of this.
In a sense, I have filled the space with the same particle repeated many 
times, whereas I would like to have an array of particles part[j] whose 
positions can be updated in time.
Does anyone know how to achieve this?  The example program:
http://www.vpython.org/vpythonprog.htm
is very clear but deals with a single object.
Furthermore, I am after 2 other things:
1)zooming and selecting a part of the scene (i.e. some specific particle 
configurations) and generating a pdf or eps or jpg or png file.
2)generating a movie. I saw there is a contributed program which should 
work only for MacOS and I wonder if there is anything similar available 
for Linux (I am running Debian testing on my box). I know this is also 
dealt with in
http://www.vpython.org/FAQ.html
but this seems to be flying over my beginner's head.
Many thanks

Lorenzo

Re: [Visualpython-users] Generating PDF and Movies in Visual Python

[Scott D. D. <Sco...@Ac...>]

Lorenzo Isella wrote:
> ...
> pos_list=s.zeros(3) # I initialize the array to contain the single 
> particle's coordinates
> my_rad=1.06/2.
> for i in xrange(0,n_part):  #n_part is the number of particles in my system
>     pos_list[0]=x_list[i]  #x_list contains a list of the x-coordinate 
> of all the particles in the system at a given time
>     pos_list[1]=y_list[i]
>     pos_list[2]=z_list[i]
>     particle=v.sphere(pos=pos_list,radius=my_rad,color=v.color.blue)
 > In a sense, I have filled the space with the same particle repeated
 > many times, whereas I would like to have an array of particles
 > part[j] whose positions can be updated in time.

Try this (to get all points in the frame):
     my_rad = 1.06 / 2.
     particles = [v.sphere(pos=loc, radius=my_rad, color=v.color.blue)
                  for loc in zip(x_list, y_list, z_list)]

> 1)zooming and selecting a part of the scene (i.e. some specific particle 
> configurations) and generating a pdf or eps or jpg or png file.
See Ruth Chabay's contributed program to go from Vpython to POV-Ray
source, then use POV-Ray to go from source to .png image.

> 2)generating a movie. I saw there is a contributed program which should 
> work only for MacOS and I wonder if there is anything similar available 
> for Linux (I am running Debian testing on my box).
First, you are not asking anything simple when you ask to go to a movie.
Your head needs to get higher if you really want to do this.  E-mail me
separately if you have everything solved up through getting .png images,
and I can provide you with "no redistribution; no comercial use" code to
take a bunch of .png files to a .mng file (which is an obscure movie
format, but there _are_ a few readers out there).

--Scott David Daniels
Sco...@Ac...