ParticleSystem = function(num, v, img_) {

  this.particles = [];
  this.origin = v.copy(); // we make sure to copy the vector value in case we accidentally mutate the original by accident
  this.img = img_
  for(let i = 0; i < num; ++i){
    this.particles.push(new Particle(this.origin, this.img));
  }
}
A basic particle system class
@param num the number of particles
@param v the origin of the particle system
@param img_ a texture for each particle in the system
@constructor