public void Draw(Graphics g)
{
foreach (ParticleGroup x in particle_groups)
{
x.Draw(g);
if (draw_aabb)
{
AABBox a = x.aabb();
g.DrawRectangle(Pens.BurlyWood, (float)a.x1, (float)a.y1, (float)(a.x2 - a.x1), (float)(a.y2 - a.y1));
}
}
g.DrawLine(Pens.Black, 0, (float)limit_Y, g.VisibleClipBounds.Width, (float)limit_Y);
}
public void Update()
{
system_step = (system_step + 1) % system_step_mod;
if (autospawn && (system_step % particle_spawn_mod == 1))
{
Spawn(spring_size);
}
// 1: Remove old particles
List <ParticleGroup> to_remove = new List <ParticleGroup>();
foreach (ParticleGroup x in particle_groups)
{
if (Math.Abs((System_step - x.born) % system_step_mod) > lifetime)
{
to_remove.Add(x);
}
}
foreach (ParticleGroup x in to_remove)
{
particle_groups.Remove(x);
}
for (int ti = 0; (ti < 1) || (normal_time && (ti) * dt < (presentation_interval / 1000.0)); ti++) //normalize for human time
//3: external forces
{
foreach (ParticleGroup x in particle_groups)
{
foreach (Particle p in x.particles)
{
p.velocity += dt * g_acceleration;
}
}
//4: damp velocities
foreach (ParticleGroup x in particle_groups)
{
foreach (Particle p in x.particles)
{
//p.velocity += kd * x.velocity + - p.velocity;
p.velocity = kd * p.velocity;
}
}
//5: predict positions (simple explicit euler)
foreach (ParticleGroup x in particle_groups)
{
foreach (Particle p in x.particles)
{
p.q = p.position + dt * p.velocity;
}
}
List <CollisionPair> collisions = new List <CollisionPair>();
//6: detect and construct collision constraints
if (compute_collisions)
{
foreach (ParticleGroup pg1 in particle_groups)
{
AABBox aabb = pg1.aabb();
foreach (ParticleGroup pg2 in particle_groups)
{
if (pg1 != pg2)
{
foreach (Particle p in pg2.particles)
{
if (aabb.is_inside(p.q))
{
collisions.Add(new CollisionPair(p, pg1));
}
}
}
}
}
}
//7: apply "projection" several times on all constraints
for (int i = 0; i < ns; i++)
{
foreach (ParticleGroup x in particle_groups)
{
// DistanceConstraints of springs
x.ProjectDistanceConstraints(in_k);
x.ProjectFloorConstraints(limit_X, limit_Y, in_k);
}
if (compute_collisions)
{
foreach (CollisionPair c in collisions)
{
c.pg.ProjectCollisionConstraint(c.p);
}
}
}
//8: find correct velocities
foreach (ParticleGroup x in particle_groups)
{
foreach (Particle p in x.particles)
{
p.velocity = (1.0 / dt) * (p.q - p.position);
p.position = p.q;
}
}
//9: apply friction and resistution impulses on velocities
//no friction or resistution is needed
}
}