Пример #1
0
  /**
   * Step the simulation. Currently anything other than 1/60f as a step leads to unpredictable
   * results - hence the default step fixes us to this step
   *
   * @param dt The amount of time to step
   */
  public void step(float dt) {
    for (int i = 0; i < bodies.size(); ++i) {
      for (int j = 0; j < sources.size(); j++) {
        ((ForceSource) sources.get(j)).apply(bodies.get(i), dt);
      }
    }

    BodyList bodies = getActiveBodies();
    JointList joints = getActiveJoints();

    float invDT = dt > 0.0f ? 1.0f / dt : 0.0f;

    if (restingBodyDetection) {
      for (int i = 0; i < bodies.size(); ++i) {
        Body b = bodies.get(i);
        b.startFrame();
      }
      for (int i = 0; i < joints.size(); ++i) {
        Joint j = joints.get(i);
        j.getBody1().setIsResting(false);
        j.getBody2().setIsResting(false);
      }
    }

    broadPhase(dt);

    for (int i = 0; i < bodies.size(); ++i) {
      Body b = bodies.get(i);

      if (b.getInvMass() == 0.0f) {
        continue;
      }
      if (b.isResting() && restingBodyDetection) {
        continue;
      }

      Vector2f temp = new Vector2f(b.getForce());
      temp.scale(b.getInvMass());
      if (b.getGravityEffected()) {
        temp.add(gravity);
      }
      temp.scale(dt);

      b.adjustVelocity(temp);

      Vector2f damping = new Vector2f(b.getVelocity());
      damping.scale(-b.getDamping() * b.getInvMass());
      b.adjustVelocity(damping);

      b.adjustAngularVelocity(dt * b.getInvI() * b.getTorque());
      b.adjustAngularVelocity(-b.getAngularVelocity() * b.getInvI() * b.getRotDamping());
    }

    for (int i = 0; i < arbiters.size(); i++) {
      Arbiter arb = arbiters.get(i);
      if (!restingBodyDetection || !arb.hasRestingPair()) {
        arb.preStep(invDT, dt, damping);
      }
    }

    for (int i = 0; i < joints.size(); ++i) {
      Joint j = joints.get(i);
      j.preStep(invDT);
    }

    for (int i = 0; i < iterations; ++i) {
      for (int k = 0; k < arbiters.size(); k++) {
        Arbiter arb = arbiters.get(k);
        if (!restingBodyDetection || !arb.hasRestingPair()) {
          arb.applyImpulse();
        } else {
          arb.getBody1().collided(arb.getBody2());
          arb.getBody2().collided(arb.getBody1());
        }
      }

      for (int k = 0; k < joints.size(); ++k) {
        Joint j = joints.get(k);
        j.applyImpulse();
      }
    }

    for (int i = 0; i < bodies.size(); ++i) {
      Body b = bodies.get(i);

      if (b.getInvMass() == 0.0f) {
        continue;
      }
      if (restingBodyDetection) {
        if (b.isResting()) {
          continue;
        }
      }

      b.adjustPosition(b.getVelocity(), dt);
      b.adjustPosition(b.getBiasedVelocity(), dt);

      b.adjustRotation(dt * b.getAngularVelocity());
      b.adjustRotation(dt * b.getBiasedAngularVelocity());

      b.resetBias();
      b.setForce(0, 0);
      b.setTorque(0);
    }

    if (restingBodyDetection) {
      for (int i = 0; i < bodies.size(); ++i) {
        Body b = bodies.get(i);
        b.endFrame();
      }
    }

    cleanUpArbiters();
  }
Пример #2
0
 /**
  * Set the gravity applied in the world
  *
  * @param x The x component of the gravity factor
  * @param y The y component of the gravity factor
  */
 public void setGravity(float x, float y) {
   gravity.x = x;
   gravity.y = y;
 }