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.
> 
>