RE: [Visualpython-users] Speed Issues

[Kuzminski, S. R <SKu...@fa...>]

I have also built up scenes that render quite slowly.

My first thought is that the constructing python code ( the code that
does the algorithms to build the shapes ) may be taking more time than
you realize, especially if you are doing something recursive.  You may
wish to organize your code so you calculate everything you need, create
a series of scenes or shapes and then line them up into a queue to be
animated ( rather than calculating the next scene on the fly ).  Of
course if a simple rotate is slow, that is harder, perhaps there is some
way of optimizing the calls to VPython so that it creates an tighter
GLCallList ( precompiled OpenGL structure that you describe )  I don't
know the VPython internals that well.

If you are operating on matrixes or arrays ( for example calculating
cellular automata ) use Numeric ( or Numarray ) matrixes, iterating over
and operating on large arrays of regular python object is slow, you can
use Numeric matrixes in expressions that are efficiently ( in C )
calculated. =20

S

-----Original Message-----
From: vis...@li...
[mailto:vis...@li...] On Behalf Of
Joel Kahn
Sent: Thursday, September 09, 2004 3:40 AM
To: vis...@li...
Subject: [Visualpython-users] Speed Issues

Jonathan Brandmeyer wrote:

>Cluster? No, I think that would=20
>be a bad idea for VPython. =20

Bad as in "not cost-effective" (sort of your next
point), or bad as in "no significant speed increase at
all in a cluster"? I'd be interested in finding out
more about whether VPython can benefit from any kind
of parallel processing.

>Any recent video card will be able=20
>to handle pretty much anything=20
>you can throw at it from VPython. =20
>A scene with several translucent=20
>and textured objects, some using a=20
>source image of 1024x2048 pixels,=20
>can be rendered in only a few ms on=20
>common PC hardware. You really=20
>can't notice that it takes any time at=20
>all, and the UI remains buttery-smooth.

I can speak only from my own experience with my 2Ghz
Athlon processor, 256MB system RAM, and S3 Graphics
ProSavageDDR card (32MB graphics RAM), usually kept in
1024x768 true-color mode, all operating under Windows
XP. In this environment, I have been able to put
together objects that caused unacceptably slow
renderings, "low virtual memory" warnings, and even
the odd system crash. When I animate some complex
scenes (usually using "rotate" commands in loops),
this can produce more issues. Mostly the problems have
resulted when I was working with either curves or
faces, and running up into thousands of points, *and*
doing fancy vector-based rotations as well. I suspect
that this is just what happens when a nut like me
starts trying to turn out artworks with a language
designed for doing physics. :-)

Seriously, though--VPython is a great system, and I
fully intend to keep exploring it; but everything has
its limits, and more powerful hardware *can* help.

Joel


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