calculate(particle, time, index) {
    this.age += time;

    if (this.age >= this.life || this.dead) {
      this.energy = 0;
      this.dead = true;
      this.destroy();
    } else {
      const scale = this.easing(particle.age / particle.life);
      this.energy = Math.max(1 - scale, 0);
    }
  }
Compute the behaviour's life cycle
@param {Proton.Particle} particle - The particle to calculate for
@param {number} time - The integrate time 1/ms
@param {number} index - The particle index