I need help with collision detection in clone game

Processing Coding Questions
1

Hi, I’m new to the world of game development with Processing and I am struggling to get my code to work. I have a good portion of it working but I cannot figure out collision detection.

Here’s the main loop:

//Create 16 spaceship objects
Spaceships[] ships = new Spaceships[16];

//Create the player object
Player p;

Bullet aBullet;
 //float spacing = 75;
 
 float x = random(50, width);
 float y = 100;
 float spacing = 75;
 int n;
 
 int px = width/2;
 int py = 650;
 boolean hasCollided = false;
 //boolean isShooting = false;
 
 float shipX;
 float shipY;
 

 

void setup(){
  size(680, 680);

  //Initialize ships
  for(int i = 0; i < ships.length; i++){
    ships[i] = new Spaceships(x, y, 50, 1, color(150)); //X coordinate, Y coordinate, size, speed, color
      //Change spacing of ships
      x += spacing;
      //If x is greater than or equal to width, add y spacing to make new line
      if(x >= width - 50 && y >= 100){
        y += spacing;
        x = 50;
      }
  }
  p = new Player(px, py, 2, 25, color(random(0, 255), random(0, 255), random(0, 255))); //X, Y, Speed, Size, Color
  aBullet = new Bullet();
}

void draw(){
  background(50, 100, 100);
  //float factor = constrain(mouseX/10, 0, 5);
  for(int i = 0; i < ships.length; i++){
    ships[i].display();
    ships[i].move();
    ships[i].hitBox();

    //p.keyPressed();
  }
    p.display();
    p.move();
    
   // aBullet.move();
    aBullet.update();
    aBullet.bulletCollision();
    

    //aBullet.bulletCollision();
   //aBullet.crash();

    
    //aBullet.display();
}

void keyPressed(){
  if(key == 'h'){
    aBullet = new Bullet();
    aBullet.update();
  }
}

Here’s the bullet class:

class Bullet{
  
  int x;
  int y;
  int xi;
  int yi;
  boolean isShooting = false;
  
  //float speed = -10;
  //float speed;
    Bullet(){
      this.x = p.x;
      this.y = p.y;
      //y = constrain(yi, 0, 0);
      //this.speed = -10;
      //speed = tempSpeed;
        
  }
  
  void display(){
    rectMode(CENTER);
    stroke(255);
    fill(255);
    rect(p.x, y - 15, 5, 5);
    //y = y - speed;
   // y += -speed;
  }
  
  void move(){
    y = y - 10;
    
  }
  
  void update(){
    move();
    display();
    //crash();
    //bulletCollision();
  }
  
  void bulletCollision(){
   if(x == shipX && y == shipY){
     println("COLLISION");
   }
  }
  
  /*
  boolean crash(){
    color detectedColor;
    for (int i = y;  i <= y; i++)
    {
      detectedColor = get(y, i);
      if (detectedColor == color(0))
      //println("COLLISION HAPPENED");
      {
        println("COLLISION AT " + y);
        return true;
      }
    }
    //println("NO COLLISION DETECTED");
    return false;
}  
*/
  
  /*
  public void simulate(){
    p.x += v.x;
    p.y += v.y;
    
    bulletCollision();
  }
  
  */
  

  
  
} //End Bullet class

Here’s the player class:

class Player{
  //Player variables
  //Go here
  int x;
  int y;
  int xSpeed;
  float pSize;
  color c;
  
  
  float bx;
  float by;
  float bSpeed = 1;
  
  
  Player(int tempX, int tempY, int xSpeed_, float pSize_, color c_){
    x = tempX;
    y = tempY;
    xSpeed = xSpeed_;
    pSize = pSize_;
    c = c_;
    bx = tempX;
    by = tempY - 15;
  }
  
    void move(){
      //x = x + xSpeed;
      
   if(keyPressed){
     if(key == 'd'){
       x = x + xSpeed;
       if(x >= width){x = width;}
      }else if(key == 'a'){
        x = x - xSpeed;
        if(x <= 0){x = 0;}
      }//else if(key == 'h'){
         // shoot(); 
      //}
   }
 }// End move()
  
  void display(){
    rectMode(CENTER);
    noStroke();
    fill(c);
    rect(x, y, pSize, pSize); //draw the player
    rect(x, y - 15, 5, 10); //player's weapon
  }
  
  
  

  /*
  void keyPressed(){
    if(key == 'd'){
      x += xSpeed;
    }else if (key == 'a'){
      x = -xSpeed;
    }
  } */
}

Here’s the spaceship class:

// Spaceships class

class Spaceships{
  float x;
  float y;
  float xSpeed;
  //float ySpeed;
  float shipSize;
  color c;
  
  
  
  Spaceships(float tempX, float tempY, float tempShipSize, float tempXSpeed, color c_){
    x = tempX;
    y = tempY;
    xSpeed = tempXSpeed;
    //xSpacing = tempXSpacing;
    shipSize = tempShipSize;
    c = c_;

  }
  
  void move(){
    x = x + xSpeed;
    shipX = x;
    shipY = y;
    if(x > width){
      xSpeed = -xSpeed;
      y += 100;
    }else if(x < 0){
      xSpeed = -xSpeed;
      y += 100;
    }else if(y > height - 100){
      y = height - 100;
    }

    
    
    /*
    if(x >= width){
      xSpeed *= -0.95;
      y += 100;
    }else if(x <= 0){
      xSpeed *= -0.95;
      y += 100;
    }
    if(y >= height - 100){
      y = height - 100;
    } */
  }
  
  
  void display(){
    float offset = shipSize / 4;
    ellipseMode(CENTER);
    rectMode(CENTER);
    strokeWeight(2);
    stroke(0);
    fill(c);
    ellipse(x, y - 10, shipSize / 2, shipSize / 2);
    ellipse(x, y, shipSize, shipSize / 2);
    
    stroke(0);
    fill(50, 100, 100);
    ellipse(x, y, offset, offset);
    ellipse(x + offset + 5, y, offset, offset);
    ellipse(x - offset - 5, y, shipSize /4, shipSize / 4);

  }
  
  public void hitBox(){
        //Ship hitboxes
    noStroke();
    fill(0, 0, 0, 0);
    rect(x, y, shipSize, shipSize - 25); //Ship hitboxes
  }
}

I know I’m doing something wrong but I have been hours trying to fix this. Any help is greatly appreciated!

Thank you,
-Mellie

2

Hello @PaddedMellie ,

Your bullets and ship will never be exactly at the same position!

Use println() statements to see what is going on.
Add a visual queue such as background() to flash when there is a collision.

This code is only comparing along the y-axis when they are within 30 pixels and flashes (code works here):

  void bulletCollision(){
   //println(x, y);
   //println(shipX, shipY);
   println(p.y, this.y);
   println(shipY);
   println();
   
   //if(x == shipX && y == shipY) // May never see this condition!
   {
   if(abs(y - shipY) <30) // If within 30!
     {
     println("COLLISION");
     background(255);
     }
   }
  }

Above is only intended to help get you started with troubleshooting tips.
It can be easily modified for x position.

Note:

I reduced the spaceships to one for testing:
Spaceships[] ships = new Spaceships[1];

It works (detects collision) with one spaceship or first spaceship if you have more than one.

Also look here for guidance:
Guidelines—Asking Questions

Keep at it!

:)

1 Like
3

Thanks a lot @glv ! I really appreciate the help! :smile: I’m going to keep at it and hopefully get my Space Invaders clone to work.

4

Consider an Arraylist of spaceships:

ArrayList example:

/**
 * ArrayList of Objects. 
 * 
 * Demonstrates the syntax for creating an ArrayList of custom objects. 
 */

//https://processing.org/reference/ArrayList.html

ArrayList<Particle> particles = new ArrayList<Particle>();
int count = 100;

void setup() 
  {
  size(500, 500);
  noStroke();
    
  for (int i = 0; i < count; i++) 
    {
    int xt = (int) random(width);
    int yt = (int) random(height);
    println(xt, yt);  
    particles.add(new Particle(xt, yt)); // adds particles    
    }
  }

void draw() 
  {
  background(0);
  
  push();
  noFill();
  strokeWeight(2);
  stroke(255, 0, 0);
  circle(mouseX, mouseY, 40);
  pop();
  
  //Loop backward to safely remove last particle
  for (int i = particles.size() - 1; i >= 0; i--) 
  
  //for (int i = 0; i<particles.size(); i++)     // Try this to see what happens!
    {
    Particle p = particles.get(i);
    
    // Remove if mouse is within 20 pixels inside circle
    if (dist(mouseX, mouseY, p.x, p.y) < 20) 
      {
      particles.remove(i);
      continue;  // exits loop once a particle is removed
      }
    
    p.update();
    p.display();
  }
}

class Particle 
  {
  float x, y;
  
  // Constructor
  Particle(int xTemp, int yTemp) 
    {
    x = xTemp;
    y = yTemp;
    }
  
  void update() 
    {
    // Future!  
    }
  
  void display() 
    {
    fill(255, 255, 0);
    circle(x, y, 10);
    }
  }

I shared the above to get you started.
ArrayLists of objects can be a challenge!

Other examples:

There may be more here:

:)