/// <summary>
/// Calculate every particle's force
/// </summary>
void CalForce()
{
Vector3 dragVector;
// Reset force that apply on the particle
for (int i = 0; i < _particles.Count; i++)
{
_particles[i].m_force.Set(0, 0, 0);
}
// Deal with gravity and resistance
for (int i = 0; i < _particles.Count; i++)
{
ParticleProperty particle = _particles[i];
if (particle.m_blocked)
{
continue;
}
// Gravity
particle.m_force += Physics.gravity * particle.m_mass;
// Air drag force
dragVector = -particle.m_velocity;
dragVector.Normalize();
particle.m_force += dragVector * particle.m_velocity.sqrMagnitude * m_DragCoef;
// Wind force
particle.m_force += m_WindForce;
}
// Deal with spring force
for (int i = 0; i < _springs.Count; i++)
{
ParticleProperty startParticle = _springs[i].m_startParticle;
ParticleProperty endParticle = _springs[i].m_endParticle;
Vector3 distance = endParticle.m_position - startParticle.m_position;
Vector3 relateVelocity = endParticle.m_velocity - startParticle.m_velocity;
float deltLength = distance.magnitude - _springs[i].m_initLength;
float springForce = _springs[i].m_kConstant * deltLength;
distance.Normalize();
Vector3 springForceVector = distance * springForce +
(_springs[i].m_dampConstant * Vector3.Dot(relateVelocity, distance)) * distance;
if (!startParticle.m_blocked)
{
startParticle.m_force += springForceVector;
}
if (!endParticle.m_blocked)
{
endParticle.m_force -= springForceVector;
}
}
}
private void Start()
{
_particles = new List <ParticleProperty>(m_segmentNum + 1);
_springs = new List <SpringProperty>(m_segmentNum);
// Initialize particles
Vector3 deltVector = (m_endPoint - m_startPoint) / m_segmentNum;
for (int i = 0; i < m_segmentNum + 1; i++)
{
ParticleProperty particle = Instantiate <ParticleProperty>(m_particlePrefab);
particle.m_position = m_startPoint + deltVector * i;
particle.m_velocity = Vector3.zero;
particle.m_acceleration = Vector3.zero;
particle.m_force = Vector3.zero;
particle.m_blocked = false;
_particles.Add(particle);
}
_particles[0].m_blocked = true; // The first particle is blocked.
// Initialize springs
float initLength = deltVector.magnitude;
for (int i = 0; i < m_segmentNum; i++)
{
SpringProperty spring = Instantiate <SpringProperty>(m_springPrefab);
spring.m_startParticle = _particles[i];
spring.m_endParticle = _particles[i + 1];
spring.m_initLength = initLength;
_springs.Add(spring);
}
// Init render property
_mesh = new Mesh();
_mesh.MarkDynamic();
_meshFilter = GetComponent <MeshFilter>();
_normals = new List <Vector3>(new Vector3[(m_segmentNum + 1) * 2]);
_uvs = new List <Vector2>(new Vector2[(m_segmentNum + 1) * 2]);
_vertices = new List <Vector3>(new Vector3[(m_segmentNum + 1) * 2]);
_triangles = new int[m_segmentNum * 6];
_meshFilter.mesh = _mesh;
}
