visualpython-users

[Visualpython-users] Monitor gamma and redblue stereo

[Bruce S. <bas...@un...>]

Dave Scherer explained to me why my grayscale calculations gave very 
dark scenes. I've put his gamma-correction formula (the second one given 
below) into the grayscale.py program found in the Contributed Programs 
at http://vpython.py. Here are his comments:

-----------------------------------------

The problem is monitor gamma.  I had forgotten that we had not
already addressed this issue.

For silly historical reasons, PC monitors have a "gamma" of
approximately 2.5.  This means that framebuffer intensity values are not
proportional to the luminance of the monitor.  For a color (r,g,b), the
monitor is actually emitting light energy approximately proportional to
(r**2.5, g**2.5, b**2.5).  This means that (1,1,1) is not just twice as
bright as (0.5, 0.5, 0.5), but more than 5 times brighter!

This is not a huge problem for many of the things people do with
computers, because color values are chosen by hand anyway (so all that
matters is that everyone uses the same color space, which is very
roughly true across PCs.  Historically, however, Macs have used a gamma
of 1.8 instead.)  It is a big problem for 3D graphics, because it makes
*all* lighting and blending calculations nonphysical unless they are
specifically gamma corrected, which is expensive and can't be done in
hardware (except after the framebuffer, see below).

To apply this to your calculation, the color (1,0,0) is really being
rendered as (.009, 0,0) instead of (.15, 0, 0).  That is indeed very
dark!  It is possible to correct for this problem as far as your
specific calculation goes:

GAMMA = 2.5
s = ( .15 * r**GAMMA + .55 * g**GAMMA + .30 * b**GAMMA ) ** (1/GAMMA)

Or, with a different set of coefficients (the above is rather odd: blue
is definitely darker than red):

s = ( .299 * r**GAMMA + .587 * g**GAMMA + .114 * b**GAMMA ) ** (1/GAMMA)

I think you will agree that this last doesn't change the brightness of a
scene much.  In red/blue (as opposed to red/cyan) mode, the brightness
*will* change a lot because the green channel, which is the most
important for luminance, is being lost.  Unfortunately there is no way
to precisely compensate for this.

The above calculation doesn't solve all of the problems of nonlinear
gamma, which makes the vertex lighting, interpolation, antialiasing,
alpha blending (if we had any), and other color calculations inaccurate
in the same way.  The correct thing to do is to correct the monitor
gamma by changing the color tables used by the video card to convert
framebuffer data to analog monitor signals.  This method is used by
almost all full-screen 3D applications.  The problem is that there is
(last I checked) no widely supported way of changing the gamma in a
single window, and changing the system gamma makes everything else on
the screen look washed out.  This is probably why we haven't dealt with
this before.

If you want to experiment with gamma correction, there is probably a
slider in your video card properties that allows you to play with it.
You should also change scene.ambient, which defaults too high for gamma
correct rendering.

Re: [Visualpython-users] Re: Mac newbie needs help

[Gary P. <pa...@in...>]

> > > There should have been a line produced by `configure` that states
this:
> > > "checking whether the C++ library supports iterator traits... "
> > > followed
> > > by "yes" or "no".  What did it say? (should be 'yes')
> >
> > no.     We're getting somewhere.  What now?
> >
>
> That is very strange, since the Apple-distributed GCC 3.1 does support
> iterator traits.
>

I got it.

The Apple Developer Tools comes with a half-dozen or so installation
packages.  The way I read the docs, it seemed that installing the one called
"Developer.pkg"  should install everything.  It seems I was mistaken.  In
addition to
"Developer", I installed "DevTools.pkg"  and  "DevSDK.pkg".    The first one
provided gcc, the second the proper libraries.

After that:  smooth as silk.  Everything compiled and installed, and I'm in
bouncing ball heaven.

I don't know if installing "Developer"  was essential, unnecessary, or
benign.  All I can vouch for is that installing all three, "Developer"
first, worked for me.

Thanks, Jonathan, for your help with this, and for all your work on the
project.

-Gary

[Visualpython-users] Re: Mac newbie needs help

[Jonathan B. <jdb...@un...>]

----- Original Message ----- 
From: "Gary Pajer" < >
To: "Jonathan Brandmeyer" < >
Sent: Friday, September 05, 2003 11:59 AM
Subject: Re: Mac newbie needs help

> > There should have been a line produced by `configure` that states this:
> > "checking whether the C++ library supports iterator traits... "
> > followed
> > by "yes" or "no".  What did it say? (should be 'yes')
>
> no.     We're getting somewhere.  What now?
>

That is very strange, since the Apple-distributed GCC 3.1 does support
iterator traits.

About 9/10 down config.log (produced by configure) there should be a verbose
description of the error produced by the failed check.  It starts with
"configure:9419: checking whether the C++ library supports iterator traits"
and should reveal the error.

-Jonathan Brandmeyer

[Visualpython-users] redblue stereo

[Bruce S. <bas...@un...>]

Actually already in the new version there exist the options scene.stereo 
= 'redblue' (and also scene.stereo = 'redcyan'), intended to make stereo 
images viewable with simple red/blue glasses (red over the left eye). 
For redblue to work the scene has to be grayscale, not color, and 
therein lies a design issue, because there is more than one way to 
convert colors to grayscale, and the conversion depends somewhat on 
context. In order to enable lots of people to participate in the 
discussion of what conversion (or conversion options, plural) is/are 
appropriate, there is a grayscale conversion routine now available in 
the "Contributed programs" section of http://vpython.org.

You can run it directly (it has a test scene in it), or you can say

from visual import *
from grayscale import *

scene.stereo = 'redblue' # or 'redcyan'
# make a color scene
grayscale(scene)
# do animation, etc. in 3D using red-blue glasses

See the comments in the program for more about the issues. Or maybe Hugh 
Fisher or John Zelle will offer a tutorial here.

Bruce Sherwood

[Visualpython-users] Mac OSX

[Bruce S. <bas...@un...>]

I neglected to say that the stereo machinery is also in the installer 
for Mac OSX (which is the same as the installer for Linux/Unix).

Bruce Sherwood

[Visualpython-users] Linux/Unix installer with stereo

[Bruce S. <bas...@un...>]

Now at http://vpython.org is an installer for Linux/Unix with the new 
stereo machinery. The download page still refers to Python 2.2, but it 
also works with Python 2.3.

Bruce Sherwood

Re: [Visualpython-users] Re: Mac newbie needs help

[Jonathan B. <jbr...@ea...>]

On Thu, 2003-09-04 at 20:39, Gary Pajer wrote:
> I'm not entirely convinced that Developer Tools installed correctly.  I
> first installed "package.pkg", which I thought was going to do the job.  It
> sure took a long time, but gcc didn't work.   I had to drill into the
> subdirectory and install "DevTools.pkg" (or something like that) to get the
> compiler running.   There are 4 or 5 other pkg's in that directory.  Should
> I install them all individually, perhaps?

I'm afraid I have no idea here, on our system it Just Worked.

Sorry,
Jonathan Brandmeyer

Re: [Visualpython-users] Re: Mac newbie needs help

[Jonathan B. <jbr...@ea...>]

On Thu, 2003-09-04 at 20:39, Gary Pajer wrote:
> OK:  I "reinstalled" Developer Tools December 2002 version (see below), and
> gcc now exists, and Numeric
>  compiled and installed nicely.
> 
>  Now:  visual won't compile.
>  I did ./configure --prefix=/sw
> 
>  and CPPSFLAGS does = -I/sw/include.
> 
>  but make quits with.
> 
>  CXX/Include/CXX_Objects.h: At global scope:
>  CXX/Include/CXX_Objects.h:968: no class template named
>  `random_access_iterator'
>     in `std'
>  CXX/Include/CXX_Objects.h:1079: no class template named
>  `random_access_iterator
>     ' in `std'
>  make[1]: *** [arrow.lo] Error 1
>  make: *** [all-recursive] Error 1


What is the output of `gcc --version` (should be  3.1 20020420
(prerelease))?

Which version of VPython are you installing (should be 2.1.1)?

There should have been a line produced by `configure` that states this:
"checking whether the C++ library supports iterator traits... " followed
by "yes" or "no".  What did it say? (should be 'yes')

I don't have this problem on our OSX box, but it was present in an
earlier version of VPython.

-Jonathan Brandmeyer

[Visualpython-users] Re: Mac newbie needs help

[Gary P. <pa...@in...>]

OK:  I "reinstalled" Developer Tools December 2002 version (see below), and
gcc now exists, and Numeric
 compiled and installed nicely.

 Now:  visual won't compile.
 I did ./configure --prefix=/sw

 and CPPSFLAGS does = -I/sw/include.

 but make quits with.

 CXX/Include/CXX_Objects.h: At global scope:
 CXX/Include/CXX_Objects.h:968: no class template named
 `random_access_iterator'
    in `std'
 CXX/Include/CXX_Objects.h:1079: no class template named
 `random_access_iterator
    ' in `std'
 make[1]: *** [arrow.lo] Error 1
 make: *** [all-recursive] Error 1


This same error was described on the list back in August 2002, but no answer
was given.
The author suggested something about gcc 3.1 vs an earlier version ... can't
comment on that.

I'm not entirely convinced that Developer Tools installed correctly.  I
first installed "package.pkg", which I thought was going to do the job.  It
sure took a long time, but gcc didn't work.   I had to drill into the
subdirectory and install "DevTools.pkg" (or something like that) to get the
compiler running.   There are 4 or 5 other pkg's in that directory.  Should
I install them all individually, perhaps?

 Any takers?

 Thanks,
 Gary

[Visualpython-users] stereo equipment

[Bruce S. <bas...@un...>]

When Hugh Fisher recently brought 'active' stereo to my attention, I 
found it a bit difficult to figure out what kind of equipment to buy. So 
I offer my experience as a novice.

I bought a PNY nVidia Quadro 750 XGL video card for about $350. The name 
"Quadro" refers to the fact that it has two double buffers, one for each 
eye (VPython draws a scene into one buffer while the screen is refreshed 
from another buffer, hence the term "double buffer").

I bought expensive shutter glasses from NuVision (now MacNaughton Inc.). 
The $270 wireless 60 GX comes with IR emitter to synchronize the glasses 
with the left/right images displayed alternately on the screen. 
Additional glasses (so several people can view the same screen 
simultaneously) cost about $250. These glasses are quite nice.

I also bought cheap $35 shutter glasses from VRex. These are less robust 
mechanically and have smaller lenses, but they work fine. The connection 
to the computer is with a wire to a connector that goes between your 
video card and your monitor (and which delivers the synch signal to the 
glasses).

John Zelle has been using 'passive' stereo. With a video card that can 
support two monitors, the program essentially generates a window twice 
the width of one view, and the card sends the right half to a computer 
projector and the left half to another computer projector. These 
projectors aim at the same screen (are located near each other), and 
they have polarizers over their lenses. You view the screen with 
'passive' polarized glasses (just polarized glasses with the 
polarization directions at right angles to each other). Both left and 
right images are simultaneously on the screen at all times, but each eye 
sees only one of the images. You have to be careful to buy a screen that 
doesn't destroy polarization; I'm told that standard screens typically 
don't work.

Bruce Sherwood

[Visualpython-users] active and passive stereo

[Bruce S. <bas...@un...>]

John Zelle has contributed to Visual code that handles both "active" and 
"passive" stereo, and this is now available in the Windows version of 
VPython (Linux/Unix to follow quickly). Many thanks to John. Also thanks 
to Hugh Fisher who contributed to an earlier version of "active" stereo 
and to the design.

This new capability is quite fantastic. Old demos leap out of the screen 
at you, with the addition of a single line of code!

 From the new documentation for displays:

scene.stereo
Stereoscopic option; scene.stereo = 'active' will render alternating 
left eye/right eye images for viewing through shutter glasses if the 
graphics system supports quad buffered stereo.

Setting scene.stereo = 'passive' will render a scene with double window 
width, for display using two polarized projectors (with viewing using 
simple passive polarized glasses for stereo).

If stereo equipment is not available, setting the option has no effect, 
and scene.stereo will have the value 'nostereo'.

(Quad buffered 'active' stereo is only available on specialised graphics 
systems that have the necessary hardware and shutter glass connector, 
such as SGI machines and PCs with nVidia Quadro or 3DLabs Wildcat 
graphics cards. It generates the illusion of depth by rendering each 
frame twice from slightly different viewpoints corresponding to the left 
and right eyes. Special shutter glasses are synchronised with the 
alternating images so that each eye sees only the matching frame, and 
our brains do the rest. It's called 'quad buffered' because there is an 
OpenGL buffer per eye, both double-buffered for smooth updating. 
'Passive' stereo requires a video card that can drive two monitors, or 
two projectors.)

scene.stereodepth
By default, the front of the scene is located at the location of the 
physical screen, which reduces eye strain. Setting scene.stereodepth = 1 
moves the center of the scene to the location of the physical screen, 
with the front half of the scene seeming to stick dramatically out of 
the screen. scene.stereodepth = 2 moves the scene fully in front of the 
physical screen, for maximally dramatic stereo effect.

Note: There is work in progress to implement "anaglyph" stereo (red/blue 
glasses) , but this isn't quite ready.

Small detail: stonehenge.py has been slightly altered to remove the 
crosshairs, which got in the way if you add stereo. None of the standard 
demos have stereo turned on, but this is trivially easy to do.

Bruce Sherwood

Re: [Visualpython-users] Mac newbie needs more help

[Aaron T. <ti...@ma...>]

On Wednesday, September 3, 2003, at 08:39 AM, Gary Pajer wrote:

>
> I did a "locate gcc" and got a bunch of headers and libraries.  
> Nothing that
> looked like an executable.  Certainly nothing in any .../bin directory.
>
> (BTW sorry this is slightly OT, but the only reason [at the moment] 
> that I
> need to resolve this is to get visual running.  I'll take this issue
> elsewhere if you want, or if you think I'll ge better results, and you 
> can
> tell me where to take it.)
>
> Is gcc something that comes with OSX (Darwin)?  or does it install 
> with the
> Developer Tools? or something else?
>

I think it is installed with Developer Tools.

> To install the Developer Tools I double clicked the "Package"  (I 
> think)
> icon in the Dev.Tools folder... I didn't touch anything in the sub
> directory.   Then I waited a very long time while the computer did
> *something*.   It must have told me that the installation was 
> successfully
> completed; I think I'd have noticed if it didn't.  Does all that sound
> right?
>

Yes, that sounds right.

> I never thought I'd say this, but I'm begining to pine for MS ...
> specifically WinXP.
>
>

Oh, no. Please don't jump :-)

When you type "which gcc", what does it tell you?

AT

Re: [Visualpython-users] Mac newbie needs more help

[Gary P. <pa...@in...>]

I did a "locate gcc" and got a bunch of headers and libraries.  Nothing that
looked like an executable.  Certainly nothing in any .../bin directory.

(BTW sorry this is slightly OT, but the only reason [at the moment] that I
need to resolve this is to get visual running.  I'll take this issue
elsewhere if you want, or if you think I'll ge better results, and you can
tell me where to take it.)

Is gcc something that comes with OSX (Darwin)?  or does it install with the
Developer Tools? or something else?

To install the Developer Tools I double clicked the "Package"  (I think)
icon in the Dev.Tools folder... I didn't touch anything in the sub
directory.   Then I waited a very long time while the computer did
*something*.   It must have told me that the installation was successfully
completed; I think I'd have noticed if it didn't.  Does all that sound
right?

I never thought I'd say this, but I'm begining to pine for MS ...
specifically WinXP.

-gary


> You may want to check that gcc is in your path. For instance, "which
> gcc" or "gcc -v" should return something that makes sense. For me,
> "which gcc" returns "/usr/local/bin".
>
> I did have one problem with the Numeric installation, which was rather
> strange. Setup gave an error because it couldn't find /sw/bin/python
> even though I ran python2.2 to set up Numeric, so I created a symbolic
> link /sw/bin/python that pointed to /sw/bin/python2.2.
>
> I assume that you specifically installed Python 2.2 from Fink and are
> using python2.2 to run your scripts.
>
> I dont' think that's the magic incantation, but talking to your
> computer with a nice voice always helps :-)
>
> AT
>

Re: [Visualpython-users] Mac newbie needs more help

[Aaron T. <ti...@ma...>]

You may want to check that gcc is in your path. For instance, "which 
gcc" or "gcc -v" should return something that makes sense. For me, 
"which gcc" returns "/usr/local/bin".

I did have one problem with the Numeric installation, which was rather 
strange. Setup gave an error because it couldn't find /sw/bin/python 
even though I ran python2.2 to set up Numeric, so I created a symbolic 
link /sw/bin/python that pointed to /sw/bin/python2.2.

I assume that you specifically installed Python 2.2 from Fink and are 
using python2.2 to run your scripts.

I dont' think that's the magic incantation, but talking to your 
computer with a nice voice always helps :-)

AT

On Saturday, August 30, 2003, at 07:30 PM, Gary Pajer wrote:

> I've got OSX 10.2  (10.2.6, I think).  Fink is installed.  python from 
> fink
> is installed and runs.
> THe December 2002 Apple Development tools are installed.
>
> I've downloaded Numeric.  When I run setup.py install, I get an error 
> "gcc
> not found".
>
> I understand that there's something really basic missing, but bear 
> with me:
> I am a complete Mac novice.
>
> What's the magic incantation?
>
> -Gary
>
>
> -------------------------------------------------------
> This sf.net email is sponsored by:ThinkGeek
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> _______________________________________________
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>

Re: [Visualpython-users] Mac newbie needs more help -- addendum

[Gary P. <pa...@in...>]

I also have a working X11.  I think I got it from fink, not Apple.  Could
that be the problem?

-g

----- Original Message ----- 
From: "Gary Pajer" <pa...@in...>
To: <vis...@li...>
Sent: Saturday, August 30, 2003 7:30 PM
Subject: [Visualpython-users] Mac newbie needs more help


> I've got OSX 10.2  (10.2.6, I think).  Fink is installed.  python from
fink
> is installed and runs.
> THe December 2002 Apple Development tools are installed.
>
> I've downloaded Numeric.  When I run setup.py install, I get an error "gcc
> not found".
>
> I understand that there's something really basic missing, but bear with
me:
> I am a complete Mac novice.
>
> What's the magic incantation?
>
> -Gary
>
>
> -------------------------------------------------------
> This sf.net email is sponsored by:ThinkGeek
> Welcome to geek heaven.
> http://thinkgeek.com/sf
> _______________________________________________
> Visualpython-users mailing list
> Vis...@li...
> https://lists.sourceforge.net/lists/listinfo/visualpython-users

[Visualpython-users] Mac newbie needs more help

[Gary P. <pa...@in...>]

I've got OSX 10.2  (10.2.6, I think).  Fink is installed.  python from fink
is installed and runs.
THe December 2002 Apple Development tools are installed.

I've downloaded Numeric.  When I run setup.py install, I get an error "gcc
not found".

I understand that there's something really basic missing, but bear with me:
I am a complete Mac novice.

What's the magic incantation?

-Gary

[Visualpython-users] Re: little bug in vpython

[Bruce S. <bas...@un...>]

Thanks to Mir Adnan Ali for reporting a bug with searches in the old 
IDLE for VPython. Though this is now superceded by the standard IDLE 
that accompanies Python 2.3, for the benefit of users of the older IDLE 
for VPython there is a new zip file posted in the section of the 
download page called "Files useful on all platforms".

Mir Adnan ALI wrote:

> hi,
> 
> in SearchDialogBase.py, replace 'col=' with 'column=' and search
> (ctrl-s) works in the vpython version of idle, otherwise i get errors,
> using debian python 2.2.3-3 and tk8.3.5-3.
> 
> the lines changed are 52, 54, and 60 in
> "visual/idle_VPython/SearchDialogBase.py".
> 
> -adnan.
> 

Re: [Visualpython-users] visual installation (Mac OS X) - suggestions

[Bruce S. <bas...@un...>]

Thanks much for the corrections! Now fixed.

Except for the one involing Numeric, which I don't understand. The 
VPython installer directions specifcally say to run "python2.2 setup.py 
install", not "python setup.py install". This is important of course, in 
order to install Numeric for use by python2.2.

Bruce Sherwood

Aaron Titus wrote:

> Jonathan (and others who are interested),
> 
> I attempted to install the newest version of vpython today using the 
> instructions at vpython.org. I first trashed Fink and Apple's X11 and 
> reinstalled Fink and X11. Everything installed well, and I can run other 
> x applications like gnuplot. For what it's worth, I have the latest 
> version of Jaguar, Apple's development tools, security patches, etc.
> 
> A couple of corrections should be made to the installation notes on the 
> vpython site:
> 
> -Change "apt-get install gtglarea" to "apt-get install gtkglarea" -- the 
> k is missing.
> 
> -Change "apt-get install python2.2.x" to "apt-get install python22" -- 
> this is officially 2.2.2-5 I think
> 
> -Change HTML page title from "Download VPython for Linux" to "Download 
> VPython for Mac OS X"
> 
> -(maybe add this as a suggestion) If installing Numeric using gives an 
> error because it can't find /sw/bin/python, then create a symbolic link 
> /sw/bin/python that points to /sw/bin/python2.2; this will allow the 
> Numeric setup script to successfully run
> 
> -Run "apt-get install pkgconfig" -- this will fix an error given by  
> visual's configure script that says that it can't find pkgconfig; 
> evidently pkgconfig wasn't installed by the other packages.
> 
> Thanks, Jonathon, for the good work on the installer. I hope this 
> feedback will help.
> 
> AT
> 
> 
> 
> 
> 
> 
> 
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[Visualpython-users] visual-2.1.1 configure gives spurious error; other packages needed

[Sanjoy M. <sa...@mr...>]

This is using a Debian 3.0 system, Pentium, kernel 2.4.20.

I had to comment out lines 9059-9061 in the configure script from
visual-2.1.1 (visual-2.1.1-20030709.tar.gz), so that they now look like:

#    { { echo "$as_me:$LINENO: error: gtkglarea is required on Unix-like systems" >&5
#echo "$as_me: error: gtkglarea is required on Unix-like systems" >&2;}
#   { (exit 1); exit 1; }; }

Without those 3 lines commented out, the configure script exits
complaining that gtkglarea is not there, even though I had already
installed it (apt-get install gtkglarea5-dev).

The same test shows up at line 9141, where I think it belongs (it's
after the code to test whether gtkglarea works), whereas the lines I
commented out are too early I think.

With the change, configure produced a makefile, but an early compile
failed because it couldn't locate gl.h which i fixed by installing
xlibmesa-dev (apt-get install xlibmesa-dev).

Now it's compiling happily.

It runs happily except that the convenience script /usr/bin/vpython
wouldn't run:

Traceback (most recent call last):
  File "/usr/lib/python2.2/site-packages/visual/idle_VPython/idle.py", line 3, in ?
    import PyShell
  File "/usr/lib/python2.2/site-packages/visual/idle_VPython/PyShell.py", line 37, in ?
    from Tkinter import *
ImportError: No module named Tkinter

But installing the Debian package python2.2-tk solved the problem.

-Sanjoy

[Visualpython-users] visual installation (Mac OS X) - suggestions

[Aaron T. <ti...@ma...>]

Jonathan (and others who are interested),

I attempted to install the newest version of vpython today using the 
instructions at vpython.org. I first trashed Fink and Apple's X11 and 
reinstalled Fink and X11. Everything installed well, and I can run 
other x applications like gnuplot. For what it's worth, I have the 
latest version of Jaguar, Apple's development tools, security patches, 
etc.

A couple of corrections should be made to the installation notes on the 
vpython site:

-Change "apt-get install gtglarea" to "apt-get install gtkglarea" -- 
the k is missing.

-Change "apt-get install python2.2.x" to "apt-get install python22" -- 
this is officially 2.2.2-5 I think

-Change HTML page title from "Download VPython for Linux" to "Download 
VPython for Mac OS X"

-(maybe add this as a suggestion) If installing Numeric using gives an 
error because it can't find /sw/bin/python, then create a symbolic link 
/sw/bin/python that points to /sw/bin/python2.2; this will allow the 
Numeric setup script to successfully run

-Run "apt-get install pkgconfig" -- this will fix an error given by  
visual's configure script that says that it can't find pkgconfig; 
evidently pkgconfig wasn't installed by the other packages.

Thanks, Jonathon, for the good work on the installer. I hope this 
feedback will help.

AT

Re: [Visualpython-users] MATLAB or VPython?

[Hans F. <H.F...@so...>]

Hi Aaron,

> > I am sure Python is the better language to learn programming (and
> > there are extensions such as VPython, GnuPlot, Scientific, Numeric etc
> > which allow you to do pretty much the same stuff as you can in MATLAB.)
> > However, we would need to know more precisely what you want to teach.
>
> I'm leaning toward using Python at this point just because students who
> have exposure to it in the physics course <snip>
Great - go for it.

> Out of curiosity, do any of the modules you mentioned (Scientific,
> Numeric, or VPython) have matrix objects, operations, and functions
> defined?

Oh yes. Numeric as all based around matrix operations (and these are
coded in C so they are fast). Scientific I mentioned, because you can
plot x-y graphs pretty much as you can in MATLAB. (I actually meant scipy.)

Please find below an example for matrix operations and for plotting.

If you use Linux, then you have more choice with respect to using
other tools (xmgrace). You might also want to look at mayavi to
visualise 2d and 3d data from within python.

Best regards,

Hans


Example:

#-----------------------------------
#
# showing how to use Numeric and scipy to imitate MATLAB behaviour
#

import scipy.gplt as plt
import Numeric, math

N = 100
a = Numeric.arange(0,3*math.pi,1.0/N)
b = Numeric.sin(a)                       #note this is a matrix operation

plt.plot(a,b)

plt.ytitle('sin(x)')
plt.title('The big title (using Gnuplot as rendering engine)')

#-----------------------------------

Re: [Visualpython-users] MATLAB or VPython?

[Jonathan B. <jbr...@ea...>]

On Wed, 2003-08-20 at 05:31, Hans Fangohr wrote:
> Aaron,
> 

> (Also, this discussion may be off-topic here.)
> 

Discussions about possible uses for VPython are certainly on-topic
here.  That kind of feedback is especially valuable, since the
Boost-based rewrite is nearing completion.

-Jonathan Brandmeyer

Re: [Visualpython-users] MATLAB or VPython?

[Hans F. <H.F...@so...>]

Aaron,

> MATLAB is extensively used in engineering courses. As I'm preparing my
> electronics course (for the first time), I'm considering whether to use
> MATLAB or not. Other tools that *may* be as useful are VPython (used
> for its computation and graphing capabilities, not necessarily it's
> animation capabilities) and Java (using the OSP, Open Source Physics
> classes at opensourcephysics.org)

It depends what exactly you want from the software. I am currently
teaching 'computing' to engineers using MATLAB. I'd love to change to
Python but it is hard to get engineers away from MATLAB (and they need
it in later modules).

I am sure Python is the better language to learn programming (and
there are extensions such as VPython, GnuPlot, Scientific, Numeric etc
which allow you to do pretty much the same stuff as you can in MATLAB.)
However, we would need to know more precisely what you want to teach.

(Also, this discussion may be off-topic here.)

Cheers,

Hans

>
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Dr Hans Fangohr

Computational Engineering & Design Research Group
School of Engineering Sciences
University of Southampton
Southampton, SO17 1BJ
United Kingdom

Location: Building 25, Room 1033
phone : +44 (0) 23 8059 8345
fax   : +44 (0) 23 8059 7082
email : fa...@so...
-------------------------------------------------

[Visualpython-users] MATLAB or VPython?

[Aaron T. <ti...@ma...>]

MATLAB is extensively used in engineering courses. As I'm preparing my 
electronics course (for the first time), I'm considering whether to use 
MATLAB or not. Other tools that *may* be as useful are VPython (used 
for its computation and graphing capabilities, not necessarily it's 
animation capabilities) and Java (using the OSP, Open Source Physics 
classes at opensourcephysics.org)

Any thoughts?

Thanks,

AT

Re: [Visualpython-users] Idle Error for Vpython for Python23

[Bruce S. <bas...@un...>]

Thanks much for the detailed history. The new VPython installer for 
Python 2.3 assumes that the new IDLE was installed by the Python 2.3 
installer and therefore doesn't install the old IDLE for VPython. I 
guess the VPython installer could try to detect that there is no IDLE 
and then not generate a shortcut to that nonexistent IDLE.

There may also be something wrong with the wording of the installation 
instructions for VPython, in that in your step 5 you say ".exe + zip 
files". The intent of the wording about those zip files was to say that 
if you used the VPython installer, there was no reason to touch those 
zip files, which are there just to make it possible for someone to 
update individual components of the VPython stuff without a full 
reinstall of VPython (e.g. new docs or demos). The only reason you got a 
copy of the old IDLE for VPython was that you used those extra zip 
files. I'll see if I can improve the wording, but our intent is to drop 
the old IDLE for VPython completely, and not have a zip file for it.

I do recommend that you get the new IDLE, which is much improved over 
the old one.

Bruce Sherwood

David Porter wrote:

>Bruce
>        I installed python23 on 2 machines today and this is what I did:
>        1. Install python23 minus Tcl   The version of Tcl that comes with python breaks the PMW-BLT connection
>        2. Install Activestate Tcl 8.4.4 into the python23 directory 
>        3. Install BLT into "c:\python23\tcl"
>        4. Install PMW into "c:\python23"
>        5. Install VPython (.exe + zip files)
>
>The idle short cut that appeared on the desk pointed to idle.pyw in "c:\python23\lib\idlelib\idle.pyw". The only file in that directory is config-main.def (refer to step 1). As I did not install Tcl, I also did not install the version of Idle which comes with python23. I found idle.pyw in "c:\python23\lib\site-packages\visual\idle_vpython\". I changed the short cut to point to the directory in which I found idle.pyw. After that everything worked fine, including PMW/BLT. It sounds like there may be a mistake in VPython which still installs idle. I wouldn't change anything other than let people like me know where to find the old vpython version of idle.
>
>        Regards
>        DRP
>
>At 11:36 AM 8/13/2003 -0400, you wrote:
>  
>
>>I don't understand. There is no visual\idle_vpython\idle.pyw anymore. Now that Python 2.3 contains an IDLE with the features of the old idle_vpython, the VPython installer no longer installs idle_vpython, and the shortcut correctly points instead to this:
>>
>>  C:\Python23\pythonw.exe C:\Python23\Lib\idlelib\idle.pyw
>>
>>The shortcut you suggest should take you nowhere. ??
>>
>>Bruce Sherwood
>>
>>David Porter wrote:
>>
>>    
>>
>>>Guys
>>>       There is a minor error in the idle Windows install. The short cut on the desktop points to the wrong location for idle. The short cut target property has to be changed to:
>>>"c:\python23\pythonw.exe c:\python23\lib\site-packages\visual\idle_vpython\idle.pyw"
>>>       Regards
>>>       DRP
>>>
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