[EMAIL PROTECTED] wrote:
> I've copied in the code I'm using below, as it's not very long -- can
> anyone help me?
I'll have some remarks:
> <--START-->
>
> from visual import *
> from random import randrange # to create random numbers
>
> numballs = 5 # number of balls
> balls = [] # a list to contain the balls
>
> # set up a box to collide with
> side_length = 100
> minx = side_length * -10
> maxx = side_length * 10
> miny = side_length * -4
> maxy = side_length * 4
>
> # create a wireframe of space
> left = curve(pos=[(minx, miny),(minx, maxy)], color = color.white)
> top = curve(pos = [(minx, maxy),(maxx, maxy)], color = color.white)
> right = curve(pos = [(maxx, maxy),(maxx, miny)], color = color.white)
> bottom = curve(pos = [(maxx, miny),(minx,miny)], color = color.white)
>
> #create some balls
> for b in range(numballs): # for each ball
> x = randrange(minx, maxx)
> y = randrange(miny, maxy)
Don't use range - use xrange. range actually creates a list of numbers,
where xrange creates a iterator that will just return the subsequent
numbers. The difference: the first solution consumes memory linear to the
number of numbers!
> balls.append(sphere(pos = (x,y), radius = 50, color = color.red)) #
> add balls
>
> dt = 0.05 # time interval
> velocity = vector(2,0.2,1) # velocity of the balls
>
> while (1==1): # forever ...
> rate(50)
> for b in range(numballs): # for each ball ...
This is a C-ism (or JAVA-ism if you like). The for-loop in python allows you
to iterate over objects in iterables. And list is one of those. So
for ball in balls:
ball.x = ...
does the trick. And if you need an index, the commonly used idiom is
for i, ball in enumerate(balls):
...
> if balls[b].x < minx: # check it hasn't overrun a boundary
> balls[b].x = maxx
> if balls[b].x > maxx:
> balls[b].minx
> if balls[b].y < miny:
> balls[b].y = maxy
> if balls[b].y > maxy:
> balls[b].y = miny
You should do that checks above _after_ you changed the coordinates, not
before!
> # NB betting this is where it's going wrong ...
> balls[b].pos = balls[b].pos + (velocity * dt) # update the
> position of the ball
This could be the problem: you are using a python tuple and a vector object
and add them. Are you sure that works? The python tuples themselves
concatenate under the +-operator. So you'd create a large tuple of
coordinate differences here.
I suppose that using a vector for the coordinates or doing the calculation
component-wise will solve the problem.
HTH,
Diez
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