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

[Bruce S. <Bru...@nc...>]

I suggest you study the VPython example program gas.py, which 
manipulates Numeric arrays without loops, then updates the pos 
attributes of all objects in a very tight loop.

The key point is that you shouldn't be dealing with individual x, y, and 
z lists or arrays but rather with arrays of <x,y,z> vectors.

Bruce Sherwood

P.S. Technical point: The production version of VPython (3.2.9) imports 
Numeric (so you don't have to explicitly import it yourself), and the 
beta version (4.beta) imports numpy.

Lorenzo Isella wrote:
> Hello,
> and thanks for your help.
> Probably I'd better make one step at the time.
> I made some progress in creating an animation; say that I have n_part 
> particles and n_config  stored configurations (i.e.snapshots of the 
> system), and that all the particles coordinates in a given configuration 
> are stored in x_list, y_list, z_list, then this is what I can do:
> 1) read the particle positions from tot_config and plot the initial 
> configuration
> 
>     my_config=0
>     for i in xrange(0,n_part):
> 
> 
>         x_list[i]=tot_config[my_conf,3*i]
>         y_list[i]=tot_config[my_conf,(3*i+1)]
>         z_list[i]=tot_config[my_conf,(3*i+2)]
> 
>   
> 
>     particles=[v.sphere(pos=loc,radius=my_rad,color=v.color.blue)\
>                for loc in zip(x_list,y_list,z_list)] 
> 
> 2) Then I can update the particle positions by reading the other 
> configurations and re-using x_list,y_list and z_list:
> 
>     for my_conf in xrange(1,n_config):
>        
>        
>         for i in xrange(0,n_part):
>                 x_list[i]=tot_config[my_conf,3*i]
>                 y_list[i]=tot_config[my_conf,(3*i+1)]
>                 z_list[i]=tot_config[my_conf,(3*i+2)]
>                 v.rate(1000)
>                 particles[i].pos=(x_list[i],y_list[i],z_list[i])   
> 
> 
> The problem of doing so is that I am "moving" only a particle at the 
> time, it takes quite some time and the resulting animations looks 
> somehow odd.
> My idea would be: first generate the particles and locate them as in the 
> initial configuration, then read the second configuration and move all 
> the particles accordingly in a single go and so on and so forth.
> However, whereas I can directly address e.g. particles[4].pos, I cannot 
> manipulate in one go all the particle positions directly via 
> particles.pos, which is why I am posting again.
> I am sure that fixing this must be a one-liner, but so far I have not 
> achieved much.
> Many thanks
> 
> Lorenzo
> 
> 
> 
>> Message: 3
>> Date: Thu, 10 Jan 2008 17:52:30 -0800
>> From: Scott David Daniels <Sco...@Ac...>
>> Subject: Re: [Visualpython-users] Generating PDF and Movies in Visual
>> 	Python
>> To: vis...@li...
>> Message-ID: <fm6hs4$rhj$1...@ge...>
>> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>>
>> 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...
>>