Integrator.java

// Modifed version of Ben Fry's integrator for interpolating between two values
public class Integrator {

  static final float ATTRACTION = 0.1f;  // formerly 0.2f
  static final float DAMPING = 0.5f;  // formerly 0.5f

  float value = 0;
  float vel   = 0;
  float accel = 0;
  float force = 0;
  float mass  = 1;

  float damping;
  float attraction;
  
  boolean targeting;
  float target;


  public Integrator() { 
    this.value = 0;
    this.damping = DAMPING;
    this.attraction = ATTRACTION;
  }


  public Integrator(float value) {
    this.value = value;
    this.damping = DAMPING;
    this.attraction = ATTRACTION;
  }


  public Integrator(float value, float attraction, float damping) {
    this.value = value;
    this.damping = damping;
    this.attraction = attraction;
  }


  public void set(float v) {
    value = v;
  }

  
  public float get() {
    return value;
  }
  
  
  public void setAttraction(float a) {
    attraction = a;
  }
  
  
  public void setDamping(float d) {
    damping = d;
  }


  public boolean update() {
    if (targeting) {
      force += attraction * (target - value);
      accel = force / mass;
      vel = (vel + accel) * damping;
      value += vel;
      force = 0;
      return (vel > 0.0001f);
    }
    return false;
  }


  public void target(float t) {
    targeting = true;
    target = t;
  }
}