Awesome Diez -- I'll give this a go tomorrow, and hopefully it will all work!!
Diez B. Roggisch wrote: > [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 -- http://mail.python.org/mailman/listinfo/python-list
