// Start is called before the first frame update
void Start()
{
_particles = new MassParticle[particleNum];
_springs = new Spring[particleNum - 1];
GameObject go = new GameObject("p0");
MassParticle p = go.AddComponent <MassParticle>();
p.mass = 1;
p.pined = true;
p.transform.parent = this.transform;
p.transform.localPosition = Vector3.zero;
_particles[0] = p;
for (int i = 1; i < particleNum; i++)
{
GameObject goS = new GameObject("p" + i);
MassParticle pS = goS.AddComponent <MassParticle>();
pS.mass = 1;
pS.transform.parent = this.transform;
pS.transform.localPosition = new Vector3(0, -i, 0);
_particles[i] = pS;
Spring s = new Spring();
s.particleA = _particles[i - 1];
s.particleB = _particles[i];
s.restLength = 1f;
_springs[i - 1] = s;
}
}
private void FixedUpdate()
{
for (int i = 0; i < _springs.Length; i++)
{
Spring s = _springs[i];
MassParticle pA = s.particleA;
MassParticle pB = s.particleB;
if (!pA.pined)
{
pA.forces += gravity * pA.mass;
Vector3 offsetA = pB.transform.position - pA.transform.position;
pA.forces += stiffness * (offsetA.magnitude - s.restLength) * offsetA.normalized;
}
if (!pB.pined)
{
pB.forces += gravity * pB.mass;
Vector3 offsetB = pA.transform.position - pB.transform.position;
pB.forces += stiffness * (offsetB.magnitude - s.restLength) * offsetB.normalized;
}
}
for (int i = 0; i < _particles.Length; i++)
{
MassParticle p = _particles[i];
p.velocity *= (1 - damping);
p.velocity += Time.fixedDeltaTime * (p.forces / p.mass);
p.transform.position += p.velocity * Time.fixedDeltaTime;
p.forces = Vector3.zero;
}
}