Removing an object in an array upon collision

Dreeww

Hi, i was wondering if anyone could help in regards to in regards collision detection void collisionDetection(){ for(int i = 0; i < aesteroidBelt.size(); i++){ Aesteroid current = aesteroidBelt.get(i);

    for(int b = 0; b < bullets.size(); b++)
    {
      Bullet currentBullet = bullets.get(b);
        if(dist()){
        bullets.remove(b);
        aesteroidBelt.remove(i);

Cant figure out the values to use for keeps telling me that booleans are not accept and only floats are.

These are the variables i have

int n=12;

PVector ship;

//Initilaizes Variables used
float bulletSpeed = 5;
float angle = 0;
float targetAngle = 0;
float rotation = 0.05;
float xSpeed = random(0.6, 2.5);
float ySpeed = random(0.6, 2.5);
float x = random(1, 590);
float y = random(1, 390);

My Aesteroids are also a random PVector every time you run this code(part which i am stuck on)

Chrisir

if(dist()){

dist expects for parameters: currentBullet.x,currentBullet.y and x,y for the Asteroid

to use remove() you must loop backward through the bullets. Change the for-loop

Dreeww

Forgot to remove the x and y variables.

this is the function im using to implement the balls and i cant seem to get the x and y coordinates for them

for (int i=0; i<n; i++)
      aesteroidBelt.add(new Aesteroid(color(255), 
      new PVector(random(height), random(width)), 
      new PVector(random(xSpeed), random(ySpeed))));

I altered the code in other to use those x and y variables and all the balls started spawning in the same spot give or take a few and would stick to the walls and not bounce

Chrisir

POST YOUR ENTIRE CODE

Normally it's x,y not y,x

Dreeww

yes

GoToLoop

https://forum.Processing.org/two/discussions/tagged/backwards

Dreeww

void collisionDetection(){
  for(int i = aesteroidBelt.size()-1; i >=0; i--)
    {
        Aesteroid current = aesteroidBelt.get(i);

    for(int b = bullets.size() -1; b >=0; b--)
    {
        Bullet currentBullet = bullets.get(b);
        if(dist(current.x, current.y, currentBullet.x, currentBullet.y) == 0 ){
        print("Hit");
        bullets.remove(b);

        aesteroidBelt.remove(i);
        }
    }
  }
}

Altered function in accordance to backwards like in the ArrayList and still no luck

Dreeww

If i add !=0 every shot will remove so im guessing theres an issue with the logical / spacing?

GoToLoop

http://www.JeffreyThompson.org/collision-detection/point-circle.php

http://studio.ProcessingTogether.com/sp/pad/export/ro.9K-kjhuONcJDZ/latest

void checkDeath() {
  for (int lenB = bullets.size(), b = lenB; b-- != 0;) {
    final Bullet u = bullets.get(b);

    for (int lenA = asteroids.size(), a = lenA; a-- != 0;)
      if (u.checkHit(asteroids.get(a))) {
        asteroids.set(a, asteroids.get(--lenA));
        bullets.set(b, bullets.get(--lenB));

        asteroids.remove(lenA);
        bullets.remove(lenB);

        score += NUM;
        println("An asteroid has been pulverized!");

        break;
      }
  }
}

Dreeww

I dont quite understand his implementation? is there anyway you could edit mine in accordance to what is wrong?

GoToLoop

You need to use break after the double remove(). L-)

GoToLoop

And you need to implement your own checkHit() method too. >-)

Dreeww

How would i go about that? isnt that what the dist function is?

GoToLoop

Collision is 1 of the most requested themes is this forum. You can always check the old answers:
https://forum.Processing.org/two/discussions/tagged?Tag=#collisions

Or read about it: http://www.JeffreyThompson.org/collision-detection/index.php

Or try to understand my own implementation: :P

boolean checkHit(Asteroid a) {
  return Asteroid.IS_CIRCLE
    ? sq(a.x - x) + sq(a.y - y) < Asteroid.RAD_SQ

    : Asteroid.RECT_MODE == CORNER
    ? x >= a.x & x < a.x+Asteroid.DIM_X
    & y >= a.y & y < a.y+Asteroid.DIM_Y

    : x >= a.x-Asteroid.RAD_X & x < a.x+Asteroid.RAD_X
    & y >= a.y-Asteroid.RAD_Y & y < a.y+Asteroid.RAD_Y;
}

kfrajer

You need to implement backward removal. For collision detection, you need to understand the basic concept. You check the distance between the two object's center against the sum of their radii. This is valid for the circular problem only.

Kf

void collisionDetection() {


  for (int i = aesteroidBelt.size()-1; i >=0 ; i--){  
    Aesteroid current = aesteroidBelt.get(i);

    for (int b = bullets.size()-1; b >=0; b--){
      Bullet currentBullet = bullets.get(b);
      if (dist(currentBullet.x, currentBullet.y, current.loc.x, current.loc.y)<(current.radius+5)) {
        bullets.remove(b);
        aesteroidBelt.remove(i);
      }
    }
  }
}

Dreeww

Wow thankyou very much