misha's cannon

Cannonball.pde

class Cannonball {
  float rad;
  color myColor;
  PVector loc; // location
  PVector v; // velocity
  PVector a; // acceleration
  float mass;
  Cannonball(float r, float x, float y, float angle) {
    rad = r;
    mass = r*10;
    myColor = getColor(random(0, 255));
    loc = new PVector(x, y);
    v = new PVector(7.5*cos(angle),7.5*sin(angle)); // initial v
    a = gravity; // always
  }

  void update() {
    v.add(a);
    loc.add(v);
    bounce();
    a = gravity; //reset acceleration
  }

  void applyForce(PVector force) {
    PVector f = PVector.div(force, mass);
    a.add(f); //net forces
  }

  void bounce() {
    if (loc.x > width-rad/2) {
      v.x *= -1; //reverse x motion
      loc.x = width-rad/2; //constraint
    }
    else if (loc.x < rad/2) {
      v.x *= -1; //reverse x motion
      loc.x = rad/2;
    }
    if (loc.y > height-rad/2) {
      v.y *= -1; //reverse y motion
      loc.y = height-rad/2;
    } 
    else if (loc.y < rad/2) {
      v.y *= -1; //reverse y motion
      loc.y = rad/2;
    }
  }

  void display() {
    stroke(myColor);
    fill(myColor);
    ellipse(loc.x, loc.y, rad, rad);
  }
  String toString() {
    return "velocity: <"+v.x+","+v.y+"> accel: <"+a.x+","+a.y+"> and it is at <"+loc.x+","+loc.y+">.";
  }
}

mishasCannon.pde

/*
misha's cannon
 */

int w = 600;
int h = 300;
float angle;
float G = 0.0981; // gravitational constant
PVector gravity;
float rad; // radius of cannonballs
ArrayList<Cannonball> launched;

void setup() {
  size(w, h);
  background(0);
  angle = PI/2;
  gravity = new PVector(0, G);
  rad = 20; //radius of cannonball
  launched = new ArrayList<Cannonball>();
}

void draw() {
  background(0);
  angle = atan(((height-rad)-mouseY)/(mouseX-rad));
  angle = constrain(angle,0,PI/2);
  stroke(255);
  fill(255);
  text("click me",width/2,height/2);
  text("angle: "+degrees(angle),rad,height-rad);
  line(0, height, 75*cos(angle), height-(75*sin(angle)));
  for (Cannonball cb : launched) {
    cb.update();
    cb.display();
  }
}

void newCB() {
  Cannonball cb = new Cannonball(rad, 0, height, angle);
  launched.add(cb);
}

void mousePressed() {
  newCB();
}