Forwarding and reversing time in physics sim

Processing Coding Questions
1 
void update(){
    steps = pos.size()-1;
    text (counter, 150,20);
    fill(255);
      text(index,200,10);
      fill(col);
    if(forward){
      
      if(index==0){
        if(pos.size()>0){
          counter = pos.size()-1;
        }
    //if(lim>0){
    //  vx += Limit(vx,lim);
    //  vy += Limit(vy,lim);
    //}else{
    
    if(vx>4){
      vx = 4;
    }
    
    if(vx<-4){
      vx = -4;
    }
    if(vy>4){
      vx = 4;
    }
    if(vy<-4){
      vx = -4;
    }
    x += vx;
    y += vy;
    
      pos.add(new PVector(x,y));
      vel.add(new PVector(vx,vy));
    }
    else if(index ==1){
      
      x = pos.get(counter).x;
      y = pos.get(counter).y;
      counter++;
      if(counter == pos.size()-1){
        index = 0;
      }
    }}
    else if(backward){
      if(counter>0){
        index = 1;
      vx = vel.get(counter).x;
      vy = vel.get(counter).y;
      x -= vx;
      y -= vy;
      //x = pos.get(counter).x;
      //y = pos.get(counter).y;
      counter --;
      if(counter<pos.size()-1){
        pos.remove(pos.size()-1);
      }
      if(counter == 0){
        index = 0;
      }
      //steps = counter;
    }}
    else if(pause){
      
    }
  };

This is the code I have for a physics sim i am writing, I want it to be able to go forward and backwards, it works fine providing that I go back completely but otherwise the pattern changes. Not sure what to do on this one.

full code

com-video-to-gif

1 Like
2

There are some Nice menus!

Chrisir

3

Thanks Chrisir, they are fully customisable, im going to add a hashmap to make click logic more intuitive. The only thing im struggling with currently is the drag function.

4

Nice! (So the Big Crunch is the right theory?)

5

Well if you right click its the big bang

6

Yes, the infinite loop theory. Could be. Recently was said by the community, that the universe after all is sphere like, not flat!

7

Oh those crazy sphere universe theorists, it all sounds like tin foil hat stuff to me!

1 Like
8

I don’t know what’s more ‘thin foiled’. Big Bounce or M-theory. Any how, I thought your art above was some thought expression.
P.S B.T.W, I think artists are thin foiled as well.

9

Lol i was making a joke

10

Your problem might be float precision –
edit sorry, didn’t see that you had a github link, haven’t looked at the full source.

1 Like
11

I partially solved by implementing a counter and not clearing the array if I go backwards. The only issue with this, is that if I added some attractors during the initial forward phase, not deleting the array means when I go backwards means that I cannot add anymore, or rather anything I add wont affect the particles until the forward counter position has reached the end of the array.