visualpython-users

[Visualpython-users] Confusion about rotating camera around an object.

[Chris L. <chr...@sp...>]

I'm trying to rotate the camera around an object:

from visual import *

scene.background = (.6,.6,.6)


from visual import frame, cylinder


groundframe = frame()

g = cylinder(frame = groundframe, radius =10 , red = 0, blue = 0, axis = 
(0,0,-.1),opacity= .2)


from visual import frame, arrow, label

opacity = 0.1
shaftwidth = .005


axisframe = frame()
labelframe = frame()

xeaxis = arrow(frame = axisframe, shaftwidth = shaftwidth, 
axis=(10,0,0), color =(1,0,0),opacity = opacity) #  xe red
xwaxis = arrow(frame = axisframe, shaftwidth = shaftwidth, 
axis=(-10,0,0), color =(0,1,1),opacity = opacity) # xw  cyan
ynaxis = arrow(frame = axisframe, shaftwidth = shaftwidth, 
axis=(0,10,0), color =(0,1,0),opacity = opacity) # yn green
ysaxis = arrow(frame = axisframe, shaftwidth = shaftwidth, 
axis=(0,-10,0), color =(1,0,1),opacity = opacity) # ys magenta
zpaxis = arrow(frame = axisframe, axis=(0,0,1), color =(0,0,1),opacity = 
opacity)    # zp blue
zmaxis =arrow(frame = axisframe, axis=(0,0,-1), color =(1,1,0),opacity = 
opacity)    # zm yellow

nlabel = label(frame = labelframe, pos = ynaxis.axis, text = 'N',opacity 
= opacity)
elabel = label(frame = labelframe, pos = xeaxis.axis, text = 'E',opacity 
= opacity)
wlabel = label(frame = labelframe, pos = xwaxis.axis, text = 'W',opacity 
= opacity)
slabel = label(frame = labelframe, pos = ysaxis.axis, text = 'S',opacity 
= opacity)


scene.forward = (0,.7,-.6)



Gives me a view over the south axis towards the centre of the frame.
I want to rotate the camera so I can look over the E W and North axis 
but maintain the overall 'display' If I had a box drawn at 0,0,0 I would 
like to look at the four vertical faces inturn. by using the rotate command.

I am trying to use rotate to enact 3 buttons which act out the following 
three commands.

scene.forward = rotate( scene.forward, axis = (0,0,-1), angle = pi/2 )
scene.forward = rotate( scene.forward, axis = (0,0,-1), angle = pi )
scene.forward = rotate( scene.forward, axis = (0,0,-1), angle = (3 *pi)/2 )

i reckon I'm not really understanding up's effect on all this but i've 
got to the randomly poking in numbers which isn't having much useful effect.

I am trying to build an environment that i can rotate easily in 90 
degree chunks at the press of a command button but maintain the overall 
'appearance'. In essence so I view the scene from a similar elevation 
above the groundplane bu the position rotated appropriately round the 
centre point.






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Re: [Visualpython-users] Editing label example... Doesn't

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

This is a serious bug, previously unnoticed (I guess because none of the 
example programs use keyboard input). Thanks much for reporting it. 
Apparently scene.kb.keys is not getting set when there's an event. This 
bug is present in the latest 4.beta11 as well.

Bruce Sherwood

Chris Lyon wrote:

>trying the following example code on windows XP with:
>
>
> >>> import sys
> >>> sys.version
>'2.4.3 (#69, Mar 29 2006, 17:35:34) [MSC v.1310 32 bit (Intel)]'
> >>> import visual
> >>> visual.version
>(4, 'beta5')
> >>>
>
>The label does not edit....? is this to be expected?
>
>
>prose = label() # initially blank text
>
>while 1:
>
>     if scene.kb.keys: # is there an event waiting to be processed?
>
>         s = scene.kb.getkey() # obtain keyboard information
>
>         if len(s) == 1:
>
>             prose.text += s # append new character
>
>         elif (s == 'backspace' or s == 'delete') and len(prose.text) > 0:
>
>             prose.text = prose.text[:-1] # erase one letter
>
>         elif s == 'shift+delete':
>
>             prose.text = '' # erase all the text
>
>
>  
>

[Visualpython-users] Editing label example... Doesn't

[Chris L. <chr...@sp...>]

trying the following example code on windows XP with:


 >>> import sys
 >>> sys.version
'2.4.3 (#69, Mar 29 2006, 17:35:34) [MSC v.1310 32 bit (Intel)]'
 >>> import visual
 >>> visual.version
(4, 'beta5')
 >>>

The label does not edit....? is this to be expected?


prose = label() # initially blank text

while 1:

     if scene.kb.keys: # is there an event waiting to be processed?

         s = scene.kb.getkey() # obtain keyboard information

         if len(s) == 1:

             prose.text += s # append new character

         elif (s == 'backspace' or s == 'delete') and len(prose.text) > 0:

             prose.text = prose.text[:-1] # erase one letter

         elif s == 'shift+delete':

             prose.text = '' # erase all the text


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[Visualpython-users] Windows: fix to problem with quitting

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

For Windows, 4.beta11 is now available at 
http://sourceforge.net/projects/visualpython. This release fixes a 
problem with quitting a program. No new version for Linux, as it didn't 
have the quitting problem.

Arthur Siegel fixed the problem. Jonathan Brandmeyer provided helpful 
background information.

There remains (at least) one serious problem on Windows, which is that 
some animations unaccountably run in a very jerky manner. The demo 
program gas.py is an example of this.

Bruce Sherwood

Re: [Visualpython-users] Mesh questions

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

I guess you're referring to a routine in the example program 
faces_heightfield.py. That's not a class that's part of Visual, it's 
just something that the author of that program (David Scherer) wrote for 
the particular purposes of that example. It doesn't do any of the things 
expected of Visual objects, nor is there any documentation of it. Feel 
free to take it and do whatever you want with it.

Bruce Sherwood

Ryan Hoban wrote:

> I have 2 questions regarding the use of the Mesh Class provided with 
> the examples.  These are perhaps trivial but I can't seem to figure 
> them out:
>  
> 1) Once I've created a Mesh Object, is there a way to turn it on and 
> off?  With most other visual objects there is an attribute "visible" 
> which I can just set to 0 to turn the object off.
>  
> 2) Is there a way to crop a mesh object to display only parts of it 
> inside some specific domain?  For example, the surface I'm working 
> with looks awkward when viewed inside a box and I'd like to take this 
> surface and just see those parts of it that lie within a sphere of 
> some radius.  This would be easy to do if I had some nice 
> parameterization of the surface in spherical coordinates, but best I 
> can tell there's no simple parameterization of this surface.
>  
> Thanks for any help you can offer,
>  
> Ryan Hoban
>  
> rf...@ma... <mailto:rf...@ma...>
>
>------------------------------------------------------------------------
>
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>  
>

[Visualpython-users] Mesh questions

[Ryan H. <rf...@ma...>]

I have 2 questions regarding the use of the Mesh Class provided with the =
examples.  These are perhaps trivial but I can't seem to figure them =
out:

1) Once I've created a Mesh Object, is there a way to turn it on and =
off?  With most other visual objects there is an attribute "visible" =
which I can just set to 0 to turn the object off.

2) Is there a way to crop a mesh object to display only parts of it =
inside some specific domain?  For example, the surface I'm working with =
looks awkward when viewed inside a box and I'd like to take this surface =
and just see those parts of it that lie within a sphere of some radius.  =
This would be easy to do if I had some nice parameterization of the =
surface in spherical coordinates, but best I can tell there's no simple =
parameterization of this surface.

Thanks for any help you can offer,

Ryan Hoban

rf...@ma...

Re: [Visualpython-users] VPython on OS X, steps forward and otherwise

[Martin C. <cos...@wa...>]

Dethe Elza wrote:
> On 4-Dec-06, at 3:28 PM, Martin Costabel wrote:
> 
>> Dethe Elza wrote:
>> []
>>>    python [vpython script]
>>> Which results in:
>>>    Fatal Python error: Interpreter not initialized (version  
>>> mismatch?)
>>>    Abort trap
>> Which python does your "python" command run? Is it the same as the  
>> one into whose site-packages directory the visual module was  
>> installed? And the same as used for compiling vpython and boost1.33?
> 
> /sw/bin/python is the first python in my path and points to /sw/bin/ 
> python2.5  As far as I can tell, it should be the same for all of  
> these cases.

Hmm, if you run "otool -L" on the cvisualmodule.so and on 
libboost_python.dylib, does any Python.framework or other libpython 
still show up?

>> With Fink, if you install for example the python25 package, you  
>> don't get a "python" executable, only "python2.5". You have to  
>> install additionally the "python" package which creates a symlink  
>> between /sw/bin/python2.5 and /sw/bin/python.
> 
> I already added that symlink manually.  Does the python package do  
> more than that?

Not much more; it makes additional symlinks for idle, pydoc, smtpd.py, 
and for the python.1 man page.

> I don't know if I remembered to note this in my earlier mail, but the  
> tip you gave about renaming -lboost_python to /sw/lib/ 
> libboost_python.a worked to get a working VPython, though still  
> crashing frequently.

Did you look at the crash logs in ~/Library/Logs/CrashReporter/? Is 
there anything systematic jumping out from them?

-- 
Martin

[Visualpython-users] Members only

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

There has been an increasing number of attempts to post spam to this 
mailing list, which requires administrator actions to discard the spam. 
Somewhat reluctantly, I've turned on automatic rejection of non-member 
postings. Very rarely there is a non-spam posting that should be 
admitted, but the administrative overhead is too great to cope with 
these rare events.

Bruce Sherwood

Re: [Visualpython-users] VPython on OS X, steps forward and otherwise

[Dethe E. <de...@li...>]

On 4-Dec-06, at 3:28 PM, Martin Costabel wrote:

> Dethe Elza wrote:
> []
>>    python [vpython script]
>> Which results in:
>>    Fatal Python error: Interpreter not initialized (version  
>> mismatch?)
>>    Abort trap
>
> Which python does your "python" command run? Is it the same as the  
> one into whose site-packages directory the visual module was  
> installed? And the same as used for compiling vpython and boost1.33?

/sw/bin/python is the first python in my path and points to /sw/bin/ 
python2.5  As far as I can tell, it should be the same for all of  
these cases.

> With Fink, if you install for example the python25 package, you  
> don't get a "python" executable, only "python2.5". You have to  
> install additionally the "python" package which creates a symlink  
> between /sw/bin/python2.5 and /sw/bin/python.

I already added that symlink manually.  Does the python package do  
more than that?

I don't know if I remembered to note this in my earlier mail, but the  
tip you gave about renaming -lboost_python to /sw/lib/ 
libboost_python.a worked to get a working VPython, though still  
crashing frequently.

--Dethe

"Say what you like about C++, but it's uninitialized variables will  
always
hold a special place in my heart. In a world where we define  
*everything*
concretely it is the last refuge of the undefined. It's the programmer's
Wild West, the untamed frontier." --Bjorn Stroustrap

Re: [Visualpython-users] VPython on OS X, steps forward and otherwise

[Martin C. <cos...@wa...>]

Dethe Elza wrote:
[]
>    python [vpython script]
> 
> Which results in:
> 
>    Fatal Python error: Interpreter not initialized (version mismatch?)
>    Abort trap

Which python does your "python" command run? Is it the same as the one 
into whose site-packages directory the visual module was installed? And 
the same as used for compiling vpython and boost1.33?

With Fink, if you install for example the python25 package, you don't 
get a "python" executable, only "python2.5". You have to install 
additionally the "python" package which creates a symlink between 
/sw/bin/python2.5 and /sw/bin/python.

-- 
Martin

Re: [Visualpython-users] VPython on OS X, steps forward and otherwise

[Dethe E. <de...@li...>]

On 3-Dec-06, at 8:28 AM, Martin Costabel wrote:

> Dethe Elza wrote:
>> On 30-Nov-06, at 12:17 PM, Martin Costabel wrote:
>>> Yes, that's what you get when you link cvisualmodule.so with  
>>> Fink's  libboost_python.dylib that was compiled with the system  
>>> python2.3.  To work around this, you can link with the static  
>>> libboost_python.a  by changing "-lboost_python" to "/sw/lib/ 
>>> libboost_python.a" at the  right place in src/Makefile.in.
>> That did it!  Thanks for being patient with me and repeating your   
>> good advice until I see it.  I now have a build of visual that   
>> supports transparency!
>
> I have now made and committed a new revision of Fink's boost1.33  
> package, version 1.33.1-1007. It builds libboost_python.dylib using  
> Fink's python, no longer with the system python framework. This  
> avoids the crash we were talking about. In fact, the new  
> libboost_python.dylib can be built with any one of Fink's python  
> versions 2.3, 2.4, or 2.5. The resulting libraries are, for all  
> intents and purposes, identical, as far as I can tell, and they can  
> be used with any of these python versions.
>
> In particular, I was able to compile the current vpython-core2 CVS  
> sources (beta10) without any patches. The entire incantation was,  
> as noted before:
>
>   sh ./autogen.sh
>   export PKG_CONFIG_PATH=/sw/lib/fontconfig2/lib/pkgconfig:/sw/lib/ 
> xft2/lib/pkgconfig:/sw/lib/freetype219/lib/pkgconfig
>   ./configure --prefix=/sw
>   make
>
> -- 
> Martin

Hi Martin,

I did the following:

   fink selfupdate
   fink update-all
   cvspurge # removes all locally-changed or added files
   cvs up  # in vpython-core2 directory
   sh ./autogen.sh
   export PKG_CONFIG_PATH=/sw/lib/fontconfig2/lib/pkgconfig:/sw/lib/ 
xft2/lib/pkgconfig:/sw/lib/freetype219/lib/pkgconfig
   ./configure --prefix=/sw
   make
   sudo make install
   python [vpython script]

Which results in:

   Fatal Python error: Interpreter not initialized (version mismatch?)
   Abort trap

What am I doing wrong?  Somewhere I seem to be missing a step.

--Dethe


"Computers are beyond dumb, they're mind-numbingly stupid. They're  
hostile, rigid, capricious, and unforgiving. They're impossibly  
demanding and they never learn anything." -- John R. Levine

Re: [Visualpython-users] Erik Thompson videos

[Erik T. <mrl...@gm...>]

Thanks for adding a link to the videos I made.  You guys have done an
amazing job with vpython in making 3D programming easy to do.

Erik

On 12/2/06, Bruce Sherwood <Bru...@nc...> wrote:
>
> There is now a link on the home page of vpython.org to a set of videos
> created by Erik Thompson to introduce newcomers to VPython.
>
> Bruce Sherwood
>
>
> -------------------------------------------------------------------------
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> your
> opinions on IT & business topics through brief surveys - and earn cash
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>

Re: [Visualpython-users] VPython on OS X, steps forward and otherwise

[Martin C. <cos...@wa...>]

Dethe Elza wrote:
> On 30-Nov-06, at 12:17 PM, Martin Costabel wrote:
> 
>> Yes, that's what you get when you link cvisualmodule.so with Fink's  
>> libboost_python.dylib that was compiled with the system python2.3.  
>> To work around this, you can link with the static libboost_python.a  
>> by changing "-lboost_python" to "/sw/lib/libboost_python.a" at the  
>> right place in src/Makefile.in.
> 
> That did it!  Thanks for being patient with me and repeating your  
> good advice until I see it.  I now have a build of visual that  
> supports transparency!

I have now made and committed a new revision of Fink's boost1.33 
package, version 1.33.1-1007. It builds libboost_python.dylib using 
Fink's python, no longer with the system python framework. This avoids 
the crash we were talking about. In fact, the new libboost_python.dylib 
can be built with any one of Fink's python versions 2.3, 2.4, or 2.5. 
The resulting libraries are, for all intents and purposes, identical, as 
far as I can tell, and they can be used with any of these python versions.

In particular, I was able to compile the current vpython-core2 CVS 
sources (beta10) without any patches. The entire incantation was, as 
noted before:

   sh ./autogen.sh
   export 
PKG_CONFIG_PATH=/sw/lib/fontconfig2/lib/pkgconfig:/sw/lib/xft2/lib/pkgconfig:/sw/lib/freetype219/lib/pkgconfig
   ./configure --prefix=/sw
   make

-- 
Martin

Re: [Visualpython-users] Graphing is finally fast

[Arthur <ajs...@op...>]

Bruce Sherwood wrote:

>At http://sourceforge.net/projects/visualpython there is finally a beta 
>version (4.beta10) for Windows and Linux which makes graphs as fast as 
>was the case in Visual 3.
>  
>
Yay Bruce.

Every step toward a Visual 4 that is *only* steps forward is exciting.

Think we are getting there.

Art

[Visualpython-users] Graphing is finally fast

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

At http://sourceforge.net/projects/visualpython there is finally a beta 
version (4.beta10) for Windows and Linux which makes graphs as fast as 
was the case in Visual 3.

There were two issues. One was that Visual 4 does scaling of user 
coordinates to OpenGL coordinates in a different way than in Visual 3 
(part of Jonathan Brandmeyer's work to give us transparency etc.), and 
it took a while to understand how in this new environment to deal with 
nonuniform axes as are found in graphs. The version 4.beta9 fixed that 
underlying problem.

The second issue turned out to be that in graph.py (visual.graph module) 
an important scrap of code was lost in moving from Visual 3 to Visual 4. 
When a new point on a graph makes it necessary to extend the graph and 
redo the axes (labels and tick marks), that scrap extended the graph a 
bit more than was needed, in the hope that the next few additions to the 
graph would fit on the larger axes. Without that scrap, the heavyweight 
work of readjusting the axes was done way too often.

Bruce Sherwood

Re: [Visualpython-users] Anaglyph stereo rendering in VPython -- could it be improved?

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

As far as I know, I'm what passes for the/an "anaglyph expert" in the 
VPython community, because I added that piece of the stereo machinery 
after the fundamental work by Hugh Fisher and John Zelle to implement 
active and passive stero. Thanks much for your detailed technical 
comments. I wasn't aware of problems -- I think the stereo capability of 
VPython has been so little used as to not evoke useful critiques. As it 
happens, I don't have difficulty myself in seeing VPython stereo in any 
of its modes. I would think that the separation problems you point to 
should also be a a problem for some viewers in active or passive stereo 
mode.

The only problem I was previously aware of had to do specifically with 
anaglyph stereo, but not with separation. The cheap 50-cent red-cyan 
glasses I use let quite a lot of the "wrong" color through each lens, 
presumably in part because of the cheap filters but also because the 
"red" phosphor of displays has a fair amount of non-red in the emission, 
and the "green" plus "blue" phosphors have a fair amount of red in them. 
So I see the other kind of ghosts: the "red" image inappropriates shows 
faintly in my right ("cyan") eye, and vice versa.

It is not true that "The anaglyph color separation in vpython is done 
strictly by masking the color channels, so they are all or none." As you 
must have noticed, the colors are pastelized, some white being added to 
both images, so that a "red" sphere is actually pink (red plus white), 
since otherwise there were be nothing for the right eye to view. 
However, you go on to say, "with no attempt to blend them the way that 
the matrix transformation in the comparison web site does," and that's 
definitely not something I took into account in my ignorance.

 From what you say it does sound important to make eye separation 
controllable by program. I say again, if separation is a problem, it is 
presumably just as serious a problem with active and passive stereo.

Thanks for the critique, and for the pointers to additional information.

Bruce Sherwood

Stanley M Sokolow wrote:

>Hi, VPythoners,
>
>I'm trying to get nice looking stereo anaglyphs of VPython models, but
>the built-in anaglyph rendering seems to have some problems for my eyes,
>and maybe everyone else's eyes, too.   I'm no expert in anaglyphs but
>have been learning lately on various Internet sites.  I bought some good
>quality red/cyan eyeglasses (with diopter compensation in the red lens)
>and a clip-on red/blue pair that I clip onto the red/cyan glasses and
>flip up or down to remove or use them as necessary for particular
>anaglyphs.   I can also clip the red/blue set onto my regular glasses to
>use alone.  When I set some of the VPython demos to render in red/cyan
>or red/blue anaglyphs (for example, "scene.stereo = 'redblue' "), the
>rendering does produce anaglyph displays but I have pretty bad
>"ghosting" problems.  That is, my eyes and brain can merge the left and
>right eye images into a stereo virtual scene only in a portion of the
>visual depth.   A significant part of the rendering has too much
>horizontal separation between the red/cyan or red/blue pair of images,
>which is beyond my capability of merging visually.  I can see the red
>and blue eye images separated rather than merged.  This is "ghosting."
>I wonder if other users have the same problem.
>
>I have seen many examples of good and bad anaglyphs on the web.  Look at 
>this red/blue anaglyph image: 
>http://www.dogfeathers.com/3d/povray/3dgdddd.html .
>Even though this is a synthetic object (that is, constructed by a 
>program, not an actual camera photograph),  it has excellent 3d and 
>little or no ghosting to my  eyes, when viewed with red/blue glasses. 
>It came from this site, which has more excellent examples:
>http://www.dogfeathers.com/3d/povray/index.html .  I haven't been able 
>to get such good, clean 3d from the VPython demos.
>
>Here's another example of remarkably good anaglyphs from computed
>objects:  http://www.dogfeathers.com/java/ccppoly.html .  Set the Java
>applet's stereo mode to "anaglyph" and its color scheme to
>"red-blue-black", put on your red/blue eyeglasses, and set the
>"sequence" to the left side of the slider, then work your way up through
>the first few "sequence" settings for an eye-popping experience.   You
>can play with image separation by adjusting a slider on the applet.
>It's also an experience to adjust the "roundness".   This display looks
>best to me when I use both of my anaglyph eyeglasses together (red/cyan
>with red/blue also).   This reduces the ghosting to almost zero, but it
>does make a rather dark image.
>
>Here's a site with astonishingly good anaglyphs that were created either
>from stereo pair photographs or from ordinary flat photographs that were
>carefully, artistically, retouched into stereo using the software
>created by the web site's Italian owner.   This is a "must-see" if you
>have stereo anaglyph eyeglasses:  http://digilander.libero.it/kems/  .
>If you don't have anaglyph stereo viewing eyeglasses, it's worth
>searching the Internet for stereo sites to buy a set (such as
>http://www.berezin.com/3d/ where I bought mine).
>
>Here are some examples of various anaglyph rendering transformations,
>which show full-color, half-color, greyscale, etc. comparisons.
>http://www.3dtv.at/Knowhow/AnaglyphComparison_en.aspx  You'll see that
>some have a lot of ghosting while others give up some or all of the
>color information in order to reduce or eliminate ghosting.  The
>anaglyph color separation in vpython is done strictly by masking the
>color channels, so they are all or none, with no attempt to blend them
>the way that the matrix transformation in the comparison web site does.
>
>I think one problem with VPython's anaglyph rendering is that the eye
>separation attribute is hardcoded to be 1/30 of the focal length of the
>camera lens. (Actually, the comment in the VPython code says 1/30 but
>the actual division is 1/60, but maybe that's a result of some other
>factor of 1/2 in there -- the math for the focal length isn't clear to
>me.)   Some people's vision need less eye separation in the anaglyph,
>resulting in less differential between the left eye and right eye images
>in the superimposed rendering.  The 1/30 rule comes from general
>experience with cameras.   Most people can see merged stereo if the
>distance between the two cameras is 1/30 of the distance from the
>cameras to the nearest object in the scene.  That's not the same as 1/30
>of the focal length of the camera lens, of course.   (But maybe due to
>the way that vpython computes its camera "focal length," the result may
>be equivalent to the photographer's 1/30 rule.  It does not seem
>equivalent to me, though.)  However, in macro (close-up) stereo
>photography the eye separation needs to be reduced and in landscape
>photography it is greatly increased to obtain a good stereo effect.
>
>I think VPython should expose the eye separation parameter (1/30 or
>whatever) as an attribute of the Python "scene" object, that is, so you
>can set the scene eye separation by "scene.eyeseparation" just as you
>can set "scene.stereodepth."  That way the display can be customized by
>the user to whatever eye separation works for his eyes.  It doesn't seem
>like a difficult change to make, since it would be quite similar to the
>other settable attributes of the scene.  It's just beyond my programming
>skills to make the change to the C++ code, otherwise I would try it
>before suggesting it here.
>
>My point in all of this is that I think VPython's anaglyph rendering
>could be better with a few changes.  Are there any comments from the
>anaglyph experts in the group?
>
>Stan Sokolow
>
>
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[Visualpython-users] Anaglyph stereo rendering in VPython -- could it be improved?

[Stanley M S. <ove...@ea...>]

Hi, VPythoners,

I'm trying to get nice looking stereo anaglyphs of VPython models, but
the built-in anaglyph rendering seems to have some problems for my eyes,
and maybe everyone else's eyes, too.   I'm no expert in anaglyphs but
have been learning lately on various Internet sites.  I bought some good
quality red/cyan eyeglasses (with diopter compensation in the red lens)
and a clip-on red/blue pair that I clip onto the red/cyan glasses and
flip up or down to remove or use them as necessary for particular
anaglyphs.   I can also clip the red/blue set onto my regular glasses to
use alone.  When I set some of the VPython demos to render in red/cyan
or red/blue anaglyphs (for example, "scene.stereo = 'redblue' "), the
rendering does produce anaglyph displays but I have pretty bad
"ghosting" problems.  That is, my eyes and brain can merge the left and
right eye images into a stereo virtual scene only in a portion of the
visual depth.   A significant part of the rendering has too much
horizontal separation between the red/cyan or red/blue pair of images,
which is beyond my capability of merging visually.  I can see the red
and blue eye images separated rather than merged.  This is "ghosting."
I wonder if other users have the same problem.

I have seen many examples of good and bad anaglyphs on the web.  Look at 
this red/blue anaglyph image: 
http://www.dogfeathers.com/3d/povray/3dgdddd.html .
Even though this is a synthetic object (that is, constructed by a 
program, not an actual camera photograph),  it has excellent 3d and 
little or no ghosting to my  eyes, when viewed with red/blue glasses. 
It came from this site, which has more excellent examples:
http://www.dogfeathers.com/3d/povray/index.html .  I haven't been able 
to get such good, clean 3d from the VPython demos.

Here's another example of remarkably good anaglyphs from computed
objects:  http://www.dogfeathers.com/java/ccppoly.html .  Set the Java
applet's stereo mode to "anaglyph" and its color scheme to
"red-blue-black", put on your red/blue eyeglasses, and set the
"sequence" to the left side of the slider, then work your way up through
the first few "sequence" settings for an eye-popping experience.   You
can play with image separation by adjusting a slider on the applet.
It's also an experience to adjust the "roundness".   This display looks
best to me when I use both of my anaglyph eyeglasses together (red/cyan
with red/blue also).   This reduces the ghosting to almost zero, but it
does make a rather dark image.

Here's a site with astonishingly good anaglyphs that were created either
from stereo pair photographs or from ordinary flat photographs that were
carefully, artistically, retouched into stereo using the software
created by the web site's Italian owner.   This is a "must-see" if you
have stereo anaglyph eyeglasses:  http://digilander.libero.it/kems/  .
If you don't have anaglyph stereo viewing eyeglasses, it's worth
searching the Internet for stereo sites to buy a set (such as
http://www.berezin.com/3d/ where I bought mine).

Here are some examples of various anaglyph rendering transformations,
which show full-color, half-color, greyscale, etc. comparisons.
http://www.3dtv.at/Knowhow/AnaglyphComparison_en.aspx  You'll see that
some have a lot of ghosting while others give up some or all of the
color information in order to reduce or eliminate ghosting.  The
anaglyph color separation in vpython is done strictly by masking the
color channels, so they are all or none, with no attempt to blend them
the way that the matrix transformation in the comparison web site does.

I think one problem with VPython's anaglyph rendering is that the eye
separation attribute is hardcoded to be 1/30 of the focal length of the
camera lens. (Actually, the comment in the VPython code says 1/30 but
the actual division is 1/60, but maybe that's a result of some other
factor of 1/2 in there -- the math for the focal length isn't clear to
me.)   Some people's vision need less eye separation in the anaglyph,
resulting in less differential between the left eye and right eye images
in the superimposed rendering.  The 1/30 rule comes from general
experience with cameras.   Most people can see merged stereo if the
distance between the two cameras is 1/30 of the distance from the
cameras to the nearest object in the scene.  That's not the same as 1/30
of the focal length of the camera lens, of course.   (But maybe due to
the way that vpython computes its camera "focal length," the result may
be equivalent to the photographer's 1/30 rule.  It does not seem
equivalent to me, though.)  However, in macro (close-up) stereo
photography the eye separation needs to be reduced and in landscape
photography it is greatly increased to obtain a good stereo effect.

I think VPython should expose the eye separation parameter (1/30 or
whatever) as an attribute of the Python "scene" object, that is, so you
can set the scene eye separation by "scene.eyeseparation" just as you
can set "scene.stereodepth."  That way the display can be customized by
the user to whatever eye separation works for his eyes.  It doesn't seem
like a difficult change to make, since it would be quite similar to the
other settable attributes of the scene.  It's just beyond my programming
skills to make the change to the C++ code, otherwise I would try it
before suggesting it here.

My point in all of this is that I think VPython's anaglyph rendering
could be better with a few changes.  Are there any comments from the
anaglyph experts in the group?

Stan Sokolow

[Visualpython-users] Erik Thompson videos

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

There is now a link on the home page of vpython.org to a set of videos 
created by Erik Thompson to introduce newcomers to VPython.

Bruce Sherwood

[Visualpython-users] 4.beta9 -- faster graphing

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

New beta test version 4.beta9 now available for Windows and Linux at 
http://sourceforge.net/projects/visualpython

Changes that handle nonuniform axes for curve, points, faces, and label, 
which makes graphing much faster than it was on 4.beta8. If you try to 
create other objects after establishing nonuniform axes an exception is 
raised. Note that scene.uniform = False was never well supported in the 
past due to the impossibility of displaying (say) an arrow in 3D if the 
scale factors on different axes were different. My impression is that 
nonuniform axes were essentially never used.

The list of "3 serious bugs" has been changed to "2 serious bugs" 
(quitting, and gas.py jerky animation).

The graphing speed for curves (gcurves) is 25 times faster than it was 
with 4.beta8, but still 7 times slower than Visual 3, though I don't 
understand why, since it seems to me that the operations are about the 
same as before. It is gcurve that needs to go as fast as possible. A 
clue is that if you specify xmin, xmax, ymin, ymax (fixed axes), the 
speed is as fast as with Visual 3, which implies that there's something 
different in resetting the scale factors in visual.graph.

The graphing speed for points (gdots) is also 25 times faster than it 
was with 4.beta8, and 5 times faster than Visual 3, where we had to plot 
the letter "o", which was very slow.

My test routine for timing performance is this:

from visual.graph import *
from time import clock
c = gcurve(color=color.yellow)
t = clock()
x = 0
while x < 100:
   c.plot(pos=(x,cos(x)))
   x += 0.01
t = clock()-t
print t

Bruce

Re: [Visualpython-users] Install on Mandriva, crashes KDE...

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

It isn't the fact that VPython crashes on his machine that is
particularly interesting.  Its that the whole desktop crashes.  That
sounds like a general OpenGL/Xserver problem to me.

-Jonathan

On Thu, 2006-11-30 at 16:24 -0800, Dethe Elza wrote:
> On 30-Nov-06, at 3:30 PM, Bruce Sherwood wrote:
> 
> > I don't understand the bit about moving site-packages from /usr/ 
> > local to
> > /usr/bin. That sounds like you compiled against a Python in /usr/local
> > but are trying to use the results with a different Python in /usr.  
> > Seems
> > like that ought to crash, as it indeed does.
> 
> Most python extensions are binary compatible across point releases,  
> as long as the pythons were compiled with the same basic options.  So  
> this does actually work, not universally, but with a lot of libraries.
> 
> --Dethe
> 
> >
> > Bruce Sherwood
> >
> > Jonathan Brandmeyer wrote:
> >
> >> Does running glxgears cause the same problem?  What does glxinfo  
> >> report?
> >>
> >> On Thu, 2006-11-30 at 22:51 +0000, chris wrote:
> >>
> >>
> >>> I've just loaded Vpython on Mandriva 2007 and it imports ok (from  
> >>> visual
> >>> import *) but upon typing
> >>> a = sphere(), the desktop crashes and I need to log in again...
> >>>
> >>> The install all went ok, but I'm a bit stumped as what to try first.
> >>>
> >>> I had to move the visual directory from /usr/local/lib/python2.4/ 
> >>> site-packages
> >>> to /usr/lib/python2.4/site-packages but other than that  
> >>> everything proceeded
> >>> as normal.
> >>>
> >>> -------------------------------------------------------------------- 
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> 
> Simple things should be declarative.  Complex things should be  
> procedural.  --Adam Bosworth
> 
> 
> 
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Re: [Visualpython-users] Install on Mandriva, crashes KDE...

[Dethe E. <de...@li...>]

On 30-Nov-06, at 3:30 PM, Bruce Sherwood wrote:

> I don't understand the bit about moving site-packages from /usr/ 
> local to
> /usr/bin. That sounds like you compiled against a Python in /usr/local
> but are trying to use the results with a different Python in /usr.  
> Seems
> like that ought to crash, as it indeed does.

Most python extensions are binary compatible across point releases,  
as long as the pythons were compiled with the same basic options.  So  
this does actually work, not universally, but with a lot of libraries.

--Dethe

>
> Bruce Sherwood
>
> Jonathan Brandmeyer wrote:
>
>> Does running glxgears cause the same problem?  What does glxinfo  
>> report?
>>
>> On Thu, 2006-11-30 at 22:51 +0000, chris wrote:
>>
>>
>>> I've just loaded Vpython on Mandriva 2007 and it imports ok (from  
>>> visual
>>> import *) but upon typing
>>> a = sphere(), the desktop crashes and I need to log in again...
>>>
>>> The install all went ok, but I'm a bit stumped as what to try first.
>>>
>>> I had to move the visual directory from /usr/local/lib/python2.4/ 
>>> site-packages
>>> to /usr/lib/python2.4/site-packages but other than that  
>>> everything proceeded
>>> as normal.
>>>
>>> -------------------------------------------------------------------- 
>>> -----
>>> Take Surveys. Earn Cash. Influence the Future of IT
>>> Join SourceForge.net's Techsay panel and you'll get the chance to  
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>>>
>>
>>
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>
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Simple things should be declarative.  Complex things should be  
procedural.  --Adam Bosworth

Re: [Visualpython-users] VPython on OS X, steps forward and otherwise

[Dethe E. <de...@li...>]

On 30-Nov-06, at 3:34 PM, Bruce Sherwood wrote:

> I'm not using any special build tools. But as of a few minutes ago
> there's a beta8 with many improvements.

Excellent, I'll check it out.

> On Windows Arthur and I are currently using MinGW in the Msys
> environment (though Arthur is interested in trying the Microsoft C++
> compiler instead). On both Windows and Ubuntu I'm following the
> instructions in INSTALL.txt, which have been significantly simplified
> for Windows thanks to Arthur.

Yay Art!

> You are correct that there is some leftover irrelevant stuff having to
> do with the fact that at one point Jonathan Brandmeyer investigated
> using scons instead of more traditional build tools.

Glad to know I was doing the right thing by ignoring scons.

Thanks for the feedback, Bruce.

--Dethe


Ninety percent of the technology hasn't even been developed yet. -- 
Tim Armstrong, Google

Re: [Visualpython-users] new beta release

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

I should add that the 4.beta8 Windows installer checks to see whether 
numpy has already been installed. If not, it installs numpy (and will 
uninstall it if you uninstall Visual). If numpy is present, the Visual 
installer doesn't do anything, and won't uninstall numpy if you 
uninstall Visual.

Because numpy is quite extensive, the Windows installer is rather large 
(4 MB).

Bruce Sherwood

Re: [Visualpython-users] VPython on OS X, steps forward and otherwise

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

I'm not using any special build tools. But as of a few minutes ago=20
there's a beta8 with many improvements.

On Windows Arthur and I are currently using MinGW in the Msys=20
environment (though Arthur is interested in trying the Microsoft C++=20
compiler instead). On both Windows and Ubuntu I'm following the=20
instructions in INSTALL.txt, which have been significantly simplified=20
for Windows thanks to Arthur.

You are correct that there is some leftover irrelevant stuff having to=20
do with the fact that at one point Jonathan Brandmeyer investigated=20
using scons instead of more traditional build tools.

Bruce Sherwood

Dethe Elza wrote:

>On 30-Nov-06, at 5:52 AM, Arthur wrote:
>
> =20
>
>>I am concerned that you are working not at the bleeding edge, but =20
>>beyond
>>it a bit. And are trying to solve problems that shouldn't be yours =20
>>- in
>>that beta8 is a work in progress that has been focusing not only on
>>numpy compatibility but on some Windows specific build issues, and =20
>>that
>>there has been some futzing with Makefile.in (that I think Bruce =20
>>checked
>>in) that address those, but without, at the moment, thinking =20
>>through the
>>crossplatform implications, mainly because we haven't finalized =20
>>what the
>>keepers are, even for Windows.
>>   =20
>>
>
>I was trying to build from the beta5 tarball, but the files Martin =20
>was using weren't in it (there are several build tools involved--not =20
>sure how/where pycompile, scons, or mkdist_osx.sh enter into the =20
>process (are they used, or just cruft left from earlier builds?).  On =20
>the other hand, now that I have gotten it to build and run (see my =20
>reply to Martin following this), I can try to repeat the process from =20
>the beta5 tarball, or selectively roll back what I have checked out =20
>from CVS.
>
> =20
>
>>That being said, I think Bruce successfully did a Linux build from the
>>cvs as late as yesterday with no apparent problems.
>>   =20
>>
>
>Excellent.  Bruce, if you're reading this, could you give me some =20
>insight into which of the build tools you're using?
>
> =20
>
>>Coming in late, but looking at your build log where everything looks
>>rather sensible.
>>
>>Is it clear where -lboost_python -lboost_thread are being found.
>>   =20
>>
>
>Martin had given me the key to this in an earlier message, but I had =20
>missed it.  Got it now.
>
> =20
>
>>Presumably you are using a binary distro of these libs that are =20
>>placing
>>them somewhere standard.  I mention it because when I have built those
>>libraries, on Linux, or Windows I have had to handle them with kid
>>gloves, re: naming and install issues.
>>   =20
>>
>
>I'm using Fink to build all of the libs.
>
> =20
>
>>Beyond those clues, which might not be clues, don't have a clue =20
>>what you
>>might be running into.
>>   =20
>>
>
>It's all helpful.  Thanks, Art!
>
> =20
>
>>Art
>>   =20
>>
>
>--Dethe
>
>values of =CE=B2 will give rise to dom --Unix prehistory
>
>
>
>------------------------------------------------------------------------=
-
>Take Surveys. Earn Cash. Influence the Future of IT
>Join SourceForge.net's Techsay panel and you'll get the chance to share =
your
>opinions on IT & business topics through brief surveys - and earn cash
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DEVDEV
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> =20
>

Re: [Visualpython-users] Install on Mandriva, crashes KDE...

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

I don't understand the bit about moving site-packages from /usr/local to 
/usr/bin. That sounds like you compiled against a Python in /usr/local 
but are trying to use the results with a different Python in /usr. Seems 
like that ought to crash, as it indeed does.

Bruce Sherwood

Jonathan Brandmeyer wrote:

>Does running glxgears cause the same problem?  What does glxinfo report?
>
>On Thu, 2006-11-30 at 22:51 +0000, chris wrote:
>  
>
>>I've just loaded Vpython on Mandriva 2007 and it imports ok (from visual 
>>import *) but upon typing 
>>a = sphere(), the desktop crashes and I need to log in again...
>>
>>The install all went ok, but I'm a bit stumped as what to try first.
>>
>>I had to move the visual directory from /usr/local/lib/python2.4/site-packages 
>>to /usr/lib/python2.4/site-packages but other than that everything proceeded 
>>as normal.
>>
>>-------------------------------------------------------------------------
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>>    
>>
>
>
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