visualpython-users

[Visualpython-users] Visual Python in a 3D Immersive Environment

[Shaun P. <sha...@an...>]

I have modified Visual Python to run on The Wedge system at the
Department of Computer Science, Australian National University. The
Wedge is a 3D Immersive Environment, which presents scenes in real 3D.
The details about The Wedge can be found at http://escience.anu.edu.au
(usage information) and http://ephebe.anu.edu.au/wedge/index.html
(technical and hardware information).
Credit must also go to Hugh Fisher (author of the Stereo Visual Python
Program) for assisting with the 3D transformation calculations. 

I have also added a couple of extras to Visual Python
New shapes: Pyramid and Frustum
New shape set: Points (which are a set of single points on the screen)
New shape attribute: Wire (when true the shape is drawn as a wire frame)

I am giving a seminar next week on the project and I hope to have
slides/screenshots/source available after that.

Now, a number of questions ....

Did anyone have problems building Visual Python under Windows from
source? (either using the Visual C++ workspace file that came supplied,
or linking the vector library)
Did anyone have any problems running any demo's under the windows build
that use vectors eg stars.py?
Can anyone confirm that the algorithms used to generate the shapes do
not follow the "winding" rules for front-facing or back-facing surfaces?

Shaun Press
Department of Systems Engineering
Research School of Information Sciences and Engineering
Australian National University

Re: [Visualpython-users] Visual Python in a 3D Immersive Environment

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

I would be interested in adding your enhancements to Visual, if you are 
willing. I haven't heard previously of the problems you report. As to 
the winding rules, where does this come up, other than in the faces 
primitive? What is the "Stereo Visual Python Program"?

Just yesterday I had an email exchange with people involved with the 
Geowall consortium (http://www.geowall.org) who use stereo projection in 
the service of geographic visualization. Their hardware configuration is 
two projectors with polarizers mounted very close together, projecting 
onto a screen that preserves polarization. They use passive polarizing 
glasses. They may try out VPython in their context.

Bruce Sherwood

Shaun Press wrote:
> I have modified Visual Python to run on The Wedge system at the
> Department of Computer Science, Australian National University. The
> Wedge is a 3D Immersive Environment, which presents scenes in real 3D.
> The details about The Wedge can be found at http://escience.anu.edu.au
> (usage information) and http://ephebe.anu.edu.au/wedge/index.html
> (technical and hardware information).
> Credit must also go to Hugh Fisher (author of the Stereo Visual Python
> Program) for assisting with the 3D transformation calculations. 
> 
> I have also added a couple of extras to Visual Python
> New shapes: Pyramid and Frustum
> New shape set: Points (which are a set of single points on the screen)
> New shape attribute: Wire (when true the shape is drawn as a wire frame)
> 
> I am giving a seminar next week on the project and I hope to have
> slides/screenshots/source available after that.
> 
> Now, a number of questions ....
> 
> Did anyone have problems building Visual Python under Windows from
> source? (either using the Visual C++ workspace file that came supplied,
> or linking the vector library)
> Did anyone have any problems running any demo's under the windows build
> that use vectors eg stars.py?
> Can anyone confirm that the algorithms used to generate the shapes do
> not follow the "winding" rules for front-facing or back-facing surfaces?
> 
> Shaun Press
> Department of Systems Engineering
> Research School of Information Sciences and Engineering
> Australian National University
> 
> 
> 
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Re: [Visualpython-users] Visual Python in a 3D Immersive Environment

[Shaun P. <sha...@an...>]

On Thu, 2003-06-05 at 11:05, Bruce Sherwood wrote:
> I would be interested in adding your enhancements to Visual, if you are 
> willing. I haven't heard previously of the problems you report. As to 
> the winding rules, where does this come up, other than in the faces 
> primitive? What is the "Stereo Visual Python Program"?
> 
As some of the enhancements are intended to extend the use of Visual
Python in the teaching/modelling environment adding them to the next
release is what I had in mind. It saves the ANU from having a "local"
version instead of a standard version.

On the topic of winding. One of the enhancements I attempted was to
replace the software lighting model with the OpenGL lighting model. The
existing model just uses white light and simulates lighting by
brightening (or dimming) the colour values for each face. Replacing it
with the OpenGL lighting system, while more complex, would allow the
addition of different coloured lights as well as adding different type
of lights (spotlights etc). 
To do this, each shape needs to have associated normals for each
surface. The clasical way to calculate this is to take 3 points on the
surface (usally the vertex points) and use the formula (v1-v2) x (v2-v3)
where <x> is the cross product operator. However the direction of the
normal depends upon whether the points are in clockwise or
anti-clockwise order. Surfaces "face" the viewer in an anti-clockwise
direction (IIRC). It appears with some of the shapes the order is a
mixture of clockwise and anti-clockwise, so some normals face the viewer
and some face away. This results in a blotchy effect on the shapes
surface. While it gives a surreal effect for the viewer, it doesn't
improve the modelling in any way.
This also has consequences for other extensions such as add textures to
shapes and making shapes transparent. 

The Stereo Visual Python program was written by Hugh Fisher to provide
fullscreen and/or quad-buffered stereo displays. He posted the details
on this list in early march. The source is at
http://cs.anu.edu.au/~hugh.fisher/3dstuff/cvisual.zip



> Just yesterday I had an email exchange with people involved with the 
> Geowall consortium (http://www.geowall.org) who use stereo projection in 
> the service of geographic visualization. Their hardware configuration is 
> two projectors with polarizers mounted very close together, projecting 
> onto a screen that preserves polarization. They use passive polarizing 
> glasses. They may try out VPython in their context.

It sound similar to the Wedge except that they have a single screen
rather than the two we use. They may be able to use Hugh's program
without much modification at all.

Re: [Visualpython-users] Visual Python in a 3D Immersive Environment

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

I see now that I hadn't paid attention to Hugh Fisher's announcement in 
March. Thanks for the pointer. I'm unclear as to what I've got when I 
pick up Fisher's zip file. That doesn't include your work, does it, Shaun?

I'm puzzled by what you say about the winding issue. Can you post a 
short test routine that shows a blotchy appearance? I've never seen this 
effect.

Bruce Sherwood

Shaun Press wrote:

> On Thu, 2003-06-05 at 11:05, Bruce Sherwood wrote:
> 
>>I would be interested in adding your enhancements to Visual, if you are 
>>willing. I haven't heard previously of the problems you report. As to 
>>the winding rules, where does this come up, other than in the faces 
>>primitive? What is the "Stereo Visual Python Program"?
>>
> 
> As some of the enhancements are intended to extend the use of Visual
> Python in the teaching/modelling environment adding them to the next
> release is what I had in mind. It saves the ANU from having a "local"
> version instead of a standard version.
> 
> On the topic of winding. One of the enhancements I attempted was to
> replace the software lighting model with the OpenGL lighting model. The
> existing model just uses white light and simulates lighting by
> brightening (or dimming) the colour values for each face. Replacing it
> with the OpenGL lighting system, while more complex, would allow the
> addition of different coloured lights as well as adding different type
> of lights (spotlights etc). 
> To do this, each shape needs to have associated normals for each
> surface. The clasical way to calculate this is to take 3 points on the
> surface (usally the vertex points) and use the formula (v1-v2) x (v2-v3)
> where <x> is the cross product operator. However the direction of the
> normal depends upon whether the points are in clockwise or
> anti-clockwise order. Surfaces "face" the viewer in an anti-clockwise
> direction (IIRC). It appears with some of the shapes the order is a
> mixture of clockwise and anti-clockwise, so some normals face the viewer
> and some face away. This results in a blotchy effect on the shapes
> surface. While it gives a surreal effect for the viewer, it doesn't
> improve the modelling in any way.
> This also has consequences for other extensions such as add textures to
> shapes and making shapes transparent. 
> 
> The Stereo Visual Python program was written by Hugh Fisher to provide
> fullscreen and/or quad-buffered stereo displays. He posted the details
> on this list in early march. The source is at
> http://cs.anu.edu.au/~hugh.fisher/3dstuff/cvisual.zip
> 
> 
> 
> 
>>Just yesterday I had an email exchange with people involved with the 
>>Geowall consortium (http://www.geowall.org) who use stereo projection in 
>>the service of geographic visualization. Their hardware configuration is 
>>two projectors with polarizers mounted very close together, projecting 
>>onto a screen that preserves polarization. They use passive polarizing 
>>glasses. They may try out VPython in their context.
> 
> 
> It sound similar to the Wedge except that they have a single screen
> rather than the two we use. They may be able to use Hugh's program
> without much modification at all.
> 
> 

Re: [Visualpython-users] Visual Python in a 3D Immersive Environment

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

On Wed, 2003-06-04 at 19:12, Shaun Press wrote:
> I have modified Visual Python to run on The Wedge system at the
> Department of Computer Science, Australian National University. The
> Wedge is a 3D Immersive Environment, which presents scenes in real 3D.
> The details about The Wedge can be found at http://escience.anu.edu.au
> (usage information) and http://ephebe.anu.edu.au/wedge/index.html
> (technical and hardware information).
> Credit must also go to Hugh Fisher (author of the Stereo Visual Python
> Program) for assisting with the 3D transformation calculations. 
> 
> I have also added a couple of extras to Visual Python
> New shapes: Pyramid and Frustum
> New shape set: Points (which are a set of single points on the screen)
> New shape attribute: Wire (when true the shape is drawn as a wire frame)

Great stuff!  Please send a diff against CVS HEAD, that will be the
easiest format for us to use.  

Right now, everything under "examples" represents our test suite for the
upcoming archetectural changes, for regression purposes.  So, please
also send some kind of documented test suite so that we can verify that
the new features' behavior doesn't get broken as things progress.

> I am giving a seminar next week on the project and I hope to have
> slides/screenshots/source available after that.
> 
> Now, a number of questions ....
> 
> Did anyone have problems building Visual Python under Windows from
> source? (either using the Visual C++ workspace file that came supplied,
> or linking the vector library)

No problems.  We are using a MSVC build environment and a MinGW build
environment for all of our testing on Windows.  An OSX box has just been
added to the fray (yesterday), as well as a pair of Linux machines:
RedHat and Debian.

> Did anyone have any problems running any demo's under the windows build
> that use vectors eg stars.py?

No problems here, that works identically for us on all platforms.

> Can anyone confirm that the algorithms used to generate the shapes do
> not follow the "winding" rules for front-facing or back-facing surfaces?

Sorry, I can't confirm or refute that.  I'm mostly focusing on the
python <-> C++ interface area.

-Jonathan Brandmeyer