Help with object collision

Kang01

I am currently working on a game where you shoot stuff down in space and I cant figure out how to check if the bullets are hitting the targets heres the code

ArrayList <Bullet> bullets;
float numOfStars = 500;
PImage spaceShip;


float [] x = new float[int(numOfStars)];
float [] y = new float[int(numOfStars)];
float [] speed = new float[int(numOfStars)];
float [] bullet;
//Bullet = new Bullet();
float bulletSpeed;
boolean Bullet;










void setup() {
   bullets = new ArrayList();
  fullScreen();
  //size(500, 400);
  background(0);
  stroke(255);
  spaceShip = loadImage("Spaceship2.png");

  noCursor();



  int i = 0;
  while (i < numOfStars) {
    x[i]= random(0, width);
    y[i] = random(0, height);
    speed[i] = random(1, 5);
    i = i +1;
  }
}


void draw() {
  background(0);
  removeToLimit(100);
  moveAll();
  displayAll();
  //bulletSpeed = bulletSpeed +5;







  //draw triangle
  //triangle(mouseX,mouseY-6,mouseX +20, mouseY,mouseX, mouseY +6);

  //rotate(radians(180));{
  image(spaceShip, mouseX-10, mouseY);
  //}

  int i = 0;
  while (i < numOfStars) {
    float co = map(speed[i], 1, 5, 100, 255);
    stroke(co);
    strokeWeight(speed[i]);
    point(x[i], y[i]);



    x[i] = x[i] -speed[i]/ 2;

    if (x[i] < 0) {
      x[i] = width;
    }
    i = i+5;
  }






  //if (mousePressed == true) {
  // Bullet = true;
  //}





  //  if (Bullet == true) {
  //    rect(mouseX -10 +bulletSpeed, mouseY, 40,10);
  //    fill(#03FC3E);


  //  }







}



class Bullet//bullet class
{
  float x;
  float y;
  float speed;
  Bullet(float tx, float ty)
  {
    x = tx;
    y = ty;
  }
  void display()
  {
     rect(x,y+20, 40,10);
     rect(x,y+80,40,10);
  fill(#03FC3E);
    //stroke(255);
    //point(x,y);
  }
  void move()
  {
    x+= 20;
  }
}

void removeToLimit(int maxLength)
{
  while(bullets.size() > maxLength)
  {
    bullets.remove(0);
  }
}
void moveAll()
{
  for(Bullet temp : bullets)
  {
    temp.move();
  }
}
void displayAll()
{
  for(Bullet temp : bullets)
  {
    temp.display();
  }
}
void mousePressed()//add a new bullet if mouse is clicked
{
  Bullet temp = new Bullet(mouseX,mouseY);
  bullets.add(temp);
}

koogs

edit post, highlight code, press ctrl-o to format.

circular collision detection is probably easiest. check distance between bullet and object is less than the sum of radius of both. but we'll know more when you format your code because it's currently unreadable.

Kang01

I am really new to processing, can you write the code for me?

kfrajer

Please check this:

https://forum.processing.org/two/discussion/comment/90483/#Comment_90483
https://forum.processing.org/two/discussion/comment/89965/#Comment_89965

Kf

Kang01

I dont get it... I have seen a lot of posts but still dont get it

jeremydouglass

@Kang01 --

In that case it sounds like you need a step by step tutorial in collision detection, with a slow, simple explanation for beginners and lots of working examples.

Here you go:

• http://www.jeffreythompson.org/collision-detection/
• http://www.jeffreythompson.org/collision-detection/point-rect.php

Kang01

I have watched plenty of tutorials, and none of them helps

Kang01

I still dont get it

kfrajer

Check this video:

The important thing here is that the technique to avoid shape overlapping and to check for collision interaction is the same. If you check the first link in my previous post, I explained there how the algorithm works.

Kf

Kang01

I just dont know how to check if two classes are colliding and I cant find anyone explaining it

Chrisir

Hello,

some advice:

house cleaning

you need to do regular house cleaning.

Throw those aways:

float [] bullet;
//Bullet = new Bullet();
float bulletSpeed;
boolean Bullet;

auto-format your code

Use ctrl-t to auto-format your code

order of things

I would recommend to order your code in a way that nothing comes behind the class or the classes. At the moment you have functions before and after the class.

Class Star

you could make a class Star similar to Bullet with a new ArrayList stars

(numOfStars should be int, not float btw.)

Collision

regarding your collision: There are no asteroids. Do you want to shoot the stars? That would be wrong technically since they are light years away.

They are just the background.

Asteroids would look cooler. Make a class Asteroid.

Collision takes now place with the stars anyway in function moveAll().

You need to loop over all bullets and for each over all stars to check if they are close. I made a new method in the Bullet class named isClose. It is using dist().

This: return dist(x, y, x1, y1)<33; just means: return true when condition is true, otherwise return false; the boolean result of the comparison < is immediately returned.

Best, Chrisir ;-)

P.S.

Sorry, kfrajer, I haven't seen your post, we wrote at the same time but you were faster.

ArrayList <Bullet> bullets;
int numOfStars = 500;
PImage spaceShip;


float [] x = new float[int(numOfStars)];
float [] y = new float[int(numOfStars)];
float [] speed = new float[int(numOfStars)];
// float [] bullet;
//Bullet = new Bullet();
//float bulletSpeed;
//boolean Bullet;

void setup() {

  fullScreen();

  //size(500, 400);
  background(0);

  bullets = new ArrayList();

  stroke(255);
  spaceShip = loadImage("Spaceship2.png");

  noCursor();

  int i = 0;
  // stars
  while (i < numOfStars) {
    x[i]= random(0, width);
    y[i] = random(0, height);
    speed[i] = random(1, 5);
    i = i +1;
  }
}

void draw() {
  background(0);
  removeToLimit(100);
  moveAll();
  displayAll();
  //bulletSpeed = bulletSpeed +5;

  //draw triangle
  //triangle(mouseX,mouseY-6,mouseX +20, mouseY,mouseX, mouseY +6);

  //rotate(radians(180));{
  //image(spaceShip, mouseX-10, mouseY);
  text("spaceShip", mouseX-10, mouseY);
  //}

  int i = 0;
  while (i < numOfStars) {
    float co = map(speed[i], 1, 5, 100, 255);
    stroke(co);
    strokeWeight(speed[i]);
    point(x[i], y[i]);



    x[i] = x[i] -speed[i]/ 2;

    if (x[i] < 0) {
      x[i] = width;
    }
    i = i+5;
  }//while
}//func

void removeToLimit(int maxLength)
{
  while (bullets.size() > maxLength )
  {
    bullets.remove(0);
  }
}

void moveAll()
{
  for (Bullet temp : bullets)
  {
    temp.move();
    int i=0; 
    while (i < numOfStars) {
      if (temp.isClose(x[i], y[i])) {
        x[i]=-10000;
        speed[i]=0;
        println("hit");
        temp.isAlive=false; 
        i=numOfStars+100;
      }//if 
      i = i+5;
    }//while
  }//for
}//func

void displayAll()
{
  for (Bullet temp : bullets)
  {
    temp.display();
  }
}

void mousePressed()//add a new bullet if mouse is clicked
{
  Bullet temp = new Bullet(mouseX, mouseY);
  bullets.add(temp);
}

// ==========================================================

class Bullet   // bullet class
{

  float x;
  float y;
  float speed;
  boolean isAlive=true; 

  Bullet(float tx, float ty)
  {
    x = tx;
    y = ty;
  }

  void display()
  {
    if (!isAlive)
      return;

    rect(x, y+20, 40, 10);
    rect(x, y+80, 40, 10);
    fill(#03FC3E);
    //stroke(255);
    //point(x,y);
  }

  void move()
  {
    x+= 20;
  }

  boolean isClose(float x1, float y1) {
    return dist(x, y, x1, y1)<33;
  }
}//class
//

Kang01

Thank you it is doing just what I wanted it to do!

Kang01

No its not done yet I will ad some space invaders :)

Chrisir

in your function removeToLimit()

you need a backward for-loop to remove() bullets if they are !isAlive or when they left the screen (x>width+110 or so)

Kang01

So what do i write?

Chrisir

IN removeToLimit PLEASE:

like

for (int i = bullets.size()-1; i>=0; i--) {
    Bullet temp = bullets.get(i); 
    // remove temp when it's away OR dead
    if(temp.x>width+110 || !temp.isAlive) {
        bullets.remove(i); 
    }//if
} // for 

not tested.

especially i>=0 might be wrong.

By the way

! means not (logical not, which is inverting the value of a boolean)

Kang01

Thanks

Kang01

Is there any way I can check for collision between the mouse and the enemies?

Chrisir

Use mouseX, mouseY in moveAll

Kang01

What syntax?

Chrisir

dist

Show your attempt

Kang01

I am, I am just really new

Chrisir

Sure

Collision between mouse and enemies

So loop over enemies and compare with mouse

Uae dist

As shown

Kang01

Well, I dont get it just dont bother I will just give up

Chrisir

I posted your solution

Which line numbers are relevant?

Don't quit so soon, kid.

Kang01

Thanks for your help, but I can't figure it out, I am just gonna try something new dont bother

Chrisir

This checks all stars against mouse

int i=0; 
while (i < numOfStars) {
  if (dist(x[i], y[i],mouseX,mouseY)<34) {
    x[i]=-10000; // move star away
    speed[i]=0;  // star stops 
    println("hit");
    //temp.isAlive=false; 
    //i=numOfStars+100;
  }//if 
  i = i+5;
}//while