Noob to Master - Physics Engine Cheat Sheet

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This is a cheat sheet for the class Noob to Master in Roskilde University

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Cheat Sheet

This cheat sheet acts as a guide to the Noob to Master physics engine.

Behaviour options

boolean vanishOnImpact	If collision, the object disappears
boolean bounceOnImpact	If collision, the object bounce
boolean constrainedInFrame	If collision with edge, the object bounce
boolean mouseUse	The object will move with the mouse
boolean keyboardUse	The object will move with the keypresses
boolean keepXConstant	The object will only move along the y axis

These boolean change how an objects react

Standard physics objects

Rectangle	Rect(position on X axis, position on Y axis, width, height, Velocity on X axis, Velocity on Y axis)
Circle	Circle(position on X axis, position on Y axis, radius of the circle, Velocity on X axis, Velocity on Y axis)

Add and physics object to the engine

PhysicsEngine PE = new PhysicsEngine();
 
public Pong() {
    p = new Player(width-30, mouseY, 10, rectSize, 0, 0);
    c = new Circle(x, y, diam, 5, 5);
    PE.add(p);
    PE.add(c);
  }

To make your object act according to the physics engine, you have to add it to the physics engine. Above we add a custom physic object called player, and a standart circle to the physics engine.

Example on custom class that extends Rect

public class Player extends Rect {
  
//Constructs a Player object and sends the needed parameters to the superclass.
  public Player(float posX, float posY, float w, float h, float xVelocity, float yVelocity) {
    super(posX, posY, w, h, xVelocity, yVelocity);
    mouseUse = true;
    keepXConstant = true;
  }
  
  void draw() {
    fill(c);
    rect(pos.x, pos.y, w, h);
    fill(255);
  }
}

Here we make a gameobject called player. It is a rectangle, uses the mouse to move and is lock on the X axis.

Tips for custom clases

You can use an image instead of a rect or circle, just insert it under the draw method in your custom object.

Ex of customClass, vanish on borderCollision.

#1
//Example on custom class that extends Circle. 
public class Shot extends Circle {
  
//Constructs a Player object and sends the needed parameters to the superclass.
  public Shot(float posX, float posY, float radius, float xVelocity, float yVelocity) {
    super(posX, posY, radius, xVelocity, yVelocity);
}

  void draw() {
    fill(c);
    ellipse(pos.x, pos.y, radius*2, radius*2);
    fill(255);  }
}

//////////////////////////

#2
void borderCollisionShot(PhysicsObject PO)
  {
    Shot shot = (Shot)PO;

    if (shot.pos.x <= shot.radius)
    {
      if (shot.gotHitX != true)
      {
        objectArray.remove(shot);
        shot.gotHitX = true;
      }
    }
/////////////////////

#3
 if (PO instanceof Shot)
        borderCollisionShot(PO);

//////////////////////////

#2
void borderCollisionShot(PhysicsObject PO)
  {
    Shot shot = (Shot)PO;

    if (shot.pos.x <= shot.radius)
    {
      if (shot.gotHitX != true)
      {
        objectArray.remove(shot);
        shot.gotHitX = true;
      }
    }
/////////////////////

Above, we made a custom class called shot. Its based on the circle class. This is marked #1.

We need to add a borderCollisionShot method, to check if there is a border collision and remove the shot from the Array.
#2 does this. This does only check one of the borders, so you have to make the rest yourself. Look at the borderCollisionCircle to get inspiration.

Then we have to finde were the physics engine checkes border collision and add in #3, so the physics engine will run the method.

More information

You can find information on all classes and methods, in the readme.txt file in the physics engine folder.

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