unsafe static void Update_Velocity(peParams *p, float dt, int begin, int end)
{
peParticle *particles = p->particles;
float particle_size2 = p->particle_size * 2.0f;
float rcp_particle_size2 = 1.0f / (p->particle_size * 2.0f);
// パーティクル同士の押し返し
for (int i = begin; i < end; ++i)
{
Vector3 pos1 = particles[i].position;
Vector3 accel = Vector3.zero;
for (int j = 0; j < p->particles_count; ++j)
{
Vector3 pos2 = particles[j].position;
Vector3 diff = pos2 - pos1;
Vector3 dir = diff * rcp_particle_size2;
float dist = diff.magnitude;
if (dist > 0.0f)
{
Vector3 a = dir * (Mathf.Min(0.0f, dist - particle_size2) * p->pressure_stiffness);
accel = accel + a;
}
}
Vector3 vel = particles[i].velocity;
vel = vel + accel * dt;
particles[i].velocity = vel;
}
// 床との衝突
Vector3 floor_normal = new Vector3(0.0f, 1.0f, 0.0f);
float floor_distance = -p->particle_size;
for (int i = begin; i < end; ++i)
{
Vector3 pos = particles[i].position;
float d = Vector3.Dot(pos, floor_normal) + floor_distance;
Vector3 accel = floor_normal * (-Mathf.Min(0.0f, d) * p->wall_stiffness);
Vector3 vel = particles[i].velocity;
vel = vel + accel * dt;
particles[i].velocity = vel;
}
// 重力加速
Vector3 gravity_direction = new Vector3(0.0f, -1.0f, 0.0f);
float gravity_strength = 5.0f;
for (int i = begin; i < end; ++i)
{
Vector3 accel = gravity_direction * gravity_strength;
Vector3 vel = particles[i].velocity;
vel = vel + accel * dt;
particles[i].velocity = vel;
}
}
unsafe static void Update_Position(peParams *p, float dt, int begin, int end)
{
peParticle *particles = p->particles;
for (int i = begin; i < end; ++i)
{
Vector3 pos = particles[i].position;
Vector3 vel = particles[i].velocity;
pos = pos + (vel * dt);
particles[i].position = pos;
}
}
