zschro_physicshacker_com/roll/old/setup.pde
import shiffman.box2d.*;
import org.jbox2d.collision.shapes.*;
import org.jbox2d.common.*;
import org.jbox2d.dynamics.*;
import org.jbox2d.dynamics.*;

void setup() {
  size(600,400);
  // Initialize box2d physics and create the world
  box2d = new Box2DProcessing(this);
  box2d.createWorld();
  // We are setting a custom gravity
  box2d.setGravity(0, -9.8);

  // Create the empty list
  particles = new ArrayList<Particle>();

  surface_vector = new ArrayList<Vec2>();
}
