public void ComputeDeltaPos(Particle particle){
		List<Particle> neighbours = particle.getNeighbours();
		Vector3D delta = new Vector3D(0,0,0);
		for(Particle neigh:neighbours){
			if(neigh.equals(particle) == false){
				Vector3D gradient = KernelGradient(particle.getPosStar(), neigh.getPosStar());
				gradient.Scale(particle.getLamda() + neigh.getLamda() + ComputeArtiPressure(particle, neigh));
				delta.Add(gradient);
			}
			
		}
		delta.Scale(1/REST_DENSITY);
		particle.setDeltaPos(delta);
	}