[Visualpython-users] Release of VPython 4.beta4

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

Now available at http://sourceforge.net/projects/visualpython for 
Windows and Linux/Unix:

Improvements to scene viewing and autoscaling, including hysteresis that 
prevents fibrillation, where the camera jitters in and out. Everywhere 
you can now use "opacity" instead of "alpha". Graph and stonehenge now 
work. Labels still problematic on Windows. Also still true that rings 
have fixed radius and setting axis other than in x direction makes mouse 
coordinates wrong. Arrows still get picked by mousing far from the arrow.

The hysteresis feature can be seen by running the example program 
bounce.py. It used to be that the camera zoomed in and out as the ball 
bounced up and down, but now the camera stays rock steady. The scheme is 
basically this: If the scene grows, move the camera back to include the 
larger scene (unless the scene is merely growing back to a previous 
size). But if the scene shrinks somewhat, don't move the camera in, 
unless the scene shrinks drastically as can happen when you're first 
assembling a scene.

The opacity vs. alpha issue is this: It has always been true that this 
property was called "opacity" in labels. In the computer graphics 
community it is often called "alpha", but not always. For example, in 
Photoshop the term "alpha" is used with many different kinds of 
graphics-associated channels, not just opacity.

In 4.beta4, you can still use alpha as a synonym for opacity, but the 
documentation (when written) will emphasize opacity.

Bruce Sherwood