[Visualpython-users] how to draw lines, 2D and 3D

[siggi <sm...@ya...>]

Hi all,

I am a complete newbie to VPython, but I got hooked. I
tried the bouncing ball, enriched it with audio from
Pygame, and the simple function plot; so little code,
so great
effects!

My first problem: how do I draw a line from x to y? I
know how to plot functions with VPython, such as
x = f(x), see above

but how do I plot a 2D function such as
x = f1(x)
y = f2(y)
draw line between x and y?

In Python it is done, e.g., like this

    while theta < 75.39:
      r = math.exp(math.cos(theta))-
        2*math.cos(4*theta)+(math.sin(theta/12))**5
     # convert from polar coordinates
      x = r*math.cos(theta)
      y = r*math.sin(theta)
      # scale to canvas size
      xx = (x*30) + 150
      yy = (y*30) + 150
      if (theta == 0.0):
        Canvas.Line(self.canvas, xx, yy, xx, yy)
      else:
        Canvas.Line(self.canvas, xOld, yOld, xx, yy)
      self.canvas.update_idletasks()
      xOld = xx
      yOld = yy
      theta = theta + 0.02

which, in this case, creates a butterfly curve
(from http://www.pythonmania.de/article/pybutt.html)

Unfortunately, browsing tutorials and documents on
www.vpython.org, I could not find a "line " command.
If there would be one, 3D "butterfly" curves
would be possible, too.

Thanks,

siggi





 
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