GravitySim

gravitysim.pde

//Make the rocket object
Rocket myRocket;
//Define planets arraylist
planets = new ArrayList();

// Global variables
//Strength of gravity
float gravstrength = -0.01;
// Thrust strength
float dv = 0.06;
//Image size
int imagesize = 200;

void setup() {
  size(600,600);
  frameRate(70);
  smooth();
  // Parameters go inside the parentheses when the object is constructed.
  myRocket = new Rocket(color(255,0,0),100,100,0.1,0.1);
}


void draw() {
  background(220);
  myRocket.drive();
  gravity();
  myRocket.display();
  
  if (keyPressed) {
    myRocket.thrust(key)
  }

  if (mousePressed && (mouseButton == LEFT)) {
    planets.add(new Planet(mouseX,mouseY));
  }
  else if (mousePressed && (mouseButton == RIGHT)) {
    for (int i=0; i<planets.size(); i++) {
      planet = planets.get(i);
      if (dist(mouseX,mouseY,planet.pos.x,planet.pos.y) < 20) {
        planets.remove(i);
      }
    }
  }
  drawplanets();
}





// Rocket has a x,y vx,vy and color
class Rocket { 
  color c;
  float x;
  float y;
  float vx;
  float vy;

  // The Constructor is defined with arguments.
  Rocket(color tc, float tx, float ty, float tvx, float tvy) { 
    c = tc;
    x = tx;
    y = ty;
    vx = tvx;
    vy = tvy;
  }
  
  void display() {
    //Draw the rocket
    stroke(0);
    fill(c);
    rectMode(CENTER);
    ellipse(x,y,10,10);
  }
  
  void thrust(string key) {
    //Apply thrust
    fill(color(255,125,0));
    if (key=='w') {
      vy -= dv;

      triangle(x-2,y+5,x+2,y+5,x,y+10);
      //rect(x,y+5,5,10);
    } else if (key=='s') {
      vy += dv;

      triangle(x-2,y-5,x+2,y-5,x,y-10);
    } else if (key=='a') {
      vx -= dv;
      triangle(x+5,y-2,x+5,y+2,x+10,y);
    } else if (key=='d') {
      vx += dv;
      triangle(x-5,y-2,x-5,y+2,x-10,y);
    }
  }

  void drive() {
    //Euler step update
    x += vx;
    y += vy;
    if (x > width || x < 0) {
      vx = -vx;
    }
    if (y > height || y < 0) {
      vy = -vy;
    }
  }
}





void drawplanets() {
  fill(color(0,0,255,10));
  for (int i=0; i< planets.size(); i++) {
    planet = planets.get(i);

    ellipse(planet.pos.x,planet.pos.y,10,10);
  }
}

void gravity() {
  PVector totforce = new PVector(0,0);

  for (int i=0; i < planets.size(); i++) {
    totforce.add(planets.get(i).force())
  }
  totforce.mult(gravstrength);
  myRocket.vx += totforce.x;
  myRocket.vy += totforce.y;
}


class Planet {
  PVector pos;
  Planet(float tx, float ty) {
    pos = new PVector(tx,ty);
  }
  PVector force() {
    PVector r = new PVector(myRocket.x,myRocket.y);
       
    r.sub(pos);
  
    float ir32 = pow(r.mag(),-3./2);
    
    r.mult(ir32);

    return r;
  }

  float pot(int i, int j) {
    float x = width/imgsize * i;
    float y = height/imgsize * j;

    float pot = gravstrength / dist(x,y,pos.x,pos.y);

    return pot;
  }
}