How to make multiples loops run at the same time?

Hello all. I am assigned to make a program in which multiple dots move at the same time. All movements are confined within a window created by user. I already have the following functions:

1. createDot(x,y,r) %make a dot with your wanted radius at certain location (x,y) in the window

2. createWin(w,h) %make a window with width and height

3. RunX(dot,unit) %move the dot x units horizontally

4. RunY(dot,unit) %move the dot y units vertically

So here is my loop to make the ball move:

ball = createDot(100,100,10)
dx = 1;
dy = 1;
n = 0;
while n < 1
      RunX(ball,dx)
      RunY(ball,dy)
      pause(0.0001) 
      refigure   %this function basically draws the dot at the new location    
      n = n + 0;
 end

I tested my code and the ball run well (Let's not worry about whether the ball goes past the created window right now).

But my problem is, I have to make multiple balls move at the same time. But when I make "ball2" and create another separate loop for it, only the first ball is moving. So I guess the 2nd ball can only start moving after the first loop of the first ball ends (which it is not supposed to).

So how can I make the 2nd ball (and later more balls) start moving at the same instant the first ball moves?

Thank you so much!

Answer 1

[Geoff Hayes]

Hi John - why not have an array of (ahem) balls each with their initial position and radius set, and then just the one while loop that iterates over each ball in the array and moves its x and y coordinates according to dx and dy:

ballArray=[];
ballArray[1] = createDot(100,100,10);
ballArray[2] = createDot(50,50,5);
% etc. for each ball

dx=1;
dy=1;

while true % just use the logical true to keep the while loop running

     % iterate over each ball (use length to get the number of balls in array)
     for i=1:length(ballArray)
         RunX(ballArray[i],dx);  % move ball i wrt x
         RunY(ballArray[i],dy);  % move ball i wrt y
     end

     pause(0.0001);
     refigure;
  end

Would the above work or do you need something where the balls have different initial start times?

Geoff

[John]

Yes everything works just fine. Except when I change dx and/or dy for one ball, all the other balls move in the exact same path as that ball. I want to make each ball's movement independent of the other's. So does that mean I have to put dx and dy as dx(i) and dy(i) ?

[Geoff Hayes]

Yes - if all the balls have different displacements, then those should be kept separate in arrays of their own, or could you update the ball object (is this an instance of some class, or is it a struct) to encapsulate that displacement information within it? So when you instantiate the ball, you could do something like:

ballArray[1] = createDot(100,100,10,1,2);

where the last two inputs are the displacements in x (dx) and y (dy).