A colleague asked me about pixel-oriented plotting in VPython, for doing
such things as chaos-related plots. I replied that there really isn't
good support for that in the production version of VPython, though the
new "points" object in the beta version is appropriate.
But then I realized that there is something one can do: Create a stack
of horizontal lines (curve objects) and set colors at points that way.
It works, and in the contributed section of vpython.org there is now a
little program pixelplot.py which makes a display of the famous
Mandelbrot set. The program also checks to see whether there is a
"points" object available and uses that, which is faster and simpler.
There's a slightly tricky issue when using curves, which is explained in
the documentation for curve. Colors are interpolated between points. So
to make the right color at a point, you have to stick in an extra point.
So 4 pixels requires 8 points on the curve: 0-1, 1-2, 2-3, 3-4.
Bruce Sherwood
P.S. In the process I found that there are bugs in the points object. It
dies when you try to append more than 33000 points. Dunno why yet. But
this doesn't affect the posted program.
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