VPython not rendering position changes

[Sam McCormack]

I am writing a VPython simulation of multiple bouncing balls. I have used a class and a list to shorten the code and easily allow for a different number of balls. However, although the code knows that the positions and momenta of the balls are changing rapidly, the display window does not render any changes. I have tested using VIDLE and Glowscript, and they both have the same issue. I used a print function to verify that the positions and momenta are changing as they should.

So, what am I doing wrong? Any help would be greatly appreciated :)

The code can be found here:

http://www.glowscript.org/#/user/TheGreatCabbage/folder/Public/program/BouncyBalls/edit

[Steve Spicklemire]

Hi Sam,

You can’t set ‘self’ in the __init__ method of your class.

Try this:

class Ball:
def __init__(self, pos, radius):
self.pos = pos
self.radius = radius
self.s = sphere(pos = self.pos, radius = self.radius, color = color.red)

then in your update loop:

ball.s.pos = ball.s.pos + ball.v * dt

-steve

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[Sam McCormack]

Thanks for your reply! That works a treat, thanks for saving me a load more time trying to figure out what was wrong with it :)