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use crate::counters::Counters;
use crate::geometry::HGrid;
use crate::math::{Point, Real, Vector};
use crate::object::Boundary;
use crate::object::Fluid;
use std::sync::RwLock;
#[cfg(feature = "parallel")]
use rayon::prelude::*;
#[derive(Copy, Clone, Debug)]
/// A particle inserted on a spacial grid.
pub enum HGridEntry {
/// A fluid particle with its fluid ID and particle ID.
FluidParticle(usize, usize),
/// A fluid particle with its boundary ID and particle ID.
BoundaryParticle(usize, usize),
}
impl HGridEntry {
/// Returns (object ID, particle ID, is_boundary).
///
/// The last tuple entry is `true` if this is a fluid particle, or `false` if it is a boundary particle.
pub fn into_tuple(self) -> (usize, usize, bool) {
match self {
HGridEntry::FluidParticle(a, b) => (a, b, false),
HGridEntry::BoundaryParticle(a, b) => (a, b, true),
}
}
}
#[derive(Copy, Clone, Debug)]
/// A contact between two particles.
///
/// If the contact is between two fluid particles, it is assumed "one-way", i.e., this contact can
/// only result in a force applied by the particle `j` to the particle `i`. The force applied by
/// `i` on `j` will result from another contacts.
/// In other words, for each par of distinct fluid particles, there will be be two symmetric contacts.
pub struct Contact {
/// The index of the first particle involved in this contact.
pub i: usize,
/// The index of the first fluid involved in this contact.
pub i_model: usize,
/// The index of the second particle involved in this contact.
pub j: usize,
/// The index of the second fluid boundary involved in this contact.
pub j_model: usize,
/// The kernel evaluated at `xi - xj` where `xi` is the position of the
/// particle `i`, and `xj` is the position of the particle `j`.
pub weight: Real,
/// The kernel gradient evaluated at `xi - xj` where `xi` is the position of the
/// particle `i`, and `xj` is the position of the particle `j`.
pub gradient: Vector<Real>,
}
impl Contact {
/// Flips this contact by swapping `i` with `j`, `i_model` with `j_model`, and by negating the gradient.
pub fn flip(&self) -> Self {
Self {
i: self.j,
i_model: self.j_model,
j: self.i,
j_model: self.i_model,
weight: self.weight,
gradient: -self.gradient,
}
}
/// Returns `true` if this contact involves a single particle with itself.
pub fn is_same_particle_contact(&self) -> bool {
self.i_model == self.j_model && self.i == self.j
}
/// Returns `true` if this contact involves two particles from the same fluid.
pub fn is_same_model_contact(&self) -> bool {
self.i_model == self.j_model
}
}
#[derive(Debug)]
/// The set of contacts affecting the particles of a single fluid.
pub struct ParticlesContacts {
// All the particle contact for one model.
// `self.contacts[i]` contains all the contacts involving the particle `i`.
contacts: Vec<RwLock<Vec<Contact>>>,
}
impl ParticlesContacts {
/// Creates an empty set of contacts.
pub fn new() -> Self {
Self {
contacts: Vec::new(),
}
}
/// The set of contacts affecting the particle `i`.
pub fn particle_contacts(&self, i: usize) -> &RwLock<Vec<Contact>> {
&self.contacts[i]
}
/// The set of mutable contacts affecting the particle `i`.
pub fn particle_contacts_mut(&mut self, i: usize) -> &mut RwLock<Vec<Contact>> {
&mut self.contacts[i]
}
/// All the contacts in this set.
///
/// The `self.contacts()[i]` contains all the contact affecting the particle `i`.
pub fn contacts(&self) -> &[RwLock<Vec<Contact>>] {
&self.contacts[..]
}
/// All the mutable contacts in this set.
///
/// The `self.contacts()[i]` contains all the contact affecting the particle `i`.
pub fn contacts_mut(&mut self) -> &mut [RwLock<Vec<Contact>>] {
&mut self.contacts[..]
}
/// The total number of contacts in this set.
pub fn len(&self) -> usize {
self.contacts.iter().map(|c| c.read().unwrap().len()).sum()
}
/// Apply a permutation to this set of contacts.
pub fn apply_permutation(&mut self, _permutation: &[usize]) {
unimplemented!()
}
}
/// Insert all the particles from the given fluids into the `grid`.
pub fn insert_fluids_to_grid(fluids: &[Fluid], grid: &mut HGrid<HGridEntry>) {
for (fluid_id, fluid) in fluids.iter().enumerate() {
for (particle_id, point) in fluid.positions.iter().enumerate() {
grid.insert(&point, HGridEntry::FluidParticle(fluid_id, particle_id));
}
}
}
/// Insert all the particles from the given boundaries into the `grid`.
pub fn insert_boundaries_to_grid(boundaries: &[Boundary], grid: &mut HGrid<HGridEntry>) {
for (boundary_id, boundary) in boundaries.iter().enumerate() {
for (particle_id, point) in boundary.positions.iter().enumerate() {
grid.insert(
&point,
HGridEntry::BoundaryParticle(boundary_id, particle_id),
);
}
}
}
/// Compute all the contacts between the particles inserted in `grid`.
pub fn compute_contacts(
counters: &mut Counters,
h: Real,
fluids: &[Fluid],
boundaries: &[Boundary],
fluid_fluid_contacts: &mut Vec<ParticlesContacts>,
fluid_boundary_contacts: &mut Vec<ParticlesContacts>,
boundary_boundary_contacts: &mut Vec<ParticlesContacts>,
grid: &HGrid<HGridEntry>,
) {
// Needed so the loop in -1..=1 bellow works.
assert_eq!(h, grid.cell_width());
counters.cd.neighborhood_search_time.resume();
fluid_fluid_contacts.resize_with(fluids.len(), || ParticlesContacts::new());
fluid_boundary_contacts.resize_with(fluids.len(), || ParticlesContacts::new());
boundary_boundary_contacts.resize_with(boundaries.len(), || ParticlesContacts::new());
for (fluid, contacts) in fluids.iter().zip(fluid_fluid_contacts.iter_mut()) {
contacts
.contacts
.iter_mut()
.for_each(|c| c.write().unwrap().clear());
contacts
.contacts
.resize_with(fluid.num_particles(), || RwLock::new(Vec::new()))
}
for (fluid, contacts) in fluids.iter().zip(fluid_boundary_contacts.iter_mut()) {
contacts
.contacts
.iter_mut()
.for_each(|c| c.write().unwrap().clear());
contacts
.contacts
.resize_with(fluid.num_particles(), || RwLock::new(Vec::new()))
}
for (boundary, contacts) in boundaries.iter().zip(boundary_boundary_contacts.iter_mut()) {
contacts
.contacts
.iter_mut()
.for_each(|c| c.write().unwrap().clear());
contacts
.contacts
.resize_with(boundary.num_particles(), || RwLock::new(Vec::new()))
}
#[cfg(feature = "dim2")]
let neighbours: [(i64, i64); 5] = [(0, 0), (0, 1), (1, -1), (1, 0), (1, 1)];
#[cfg(feature = "dim3")]
let neighbours: [(i64, i64, i64); 14] = [
(0, 0, 0),
(0, 0, 1),
(0, 1, -1),
(0, 1, 0),
(0, 1, 1),
(1, -1, -1),
(1, -1, 0),
(1, -1, 1),
(1, 0, -1),
(1, 0, 0),
(1, 0, 1),
(1, 1, -1),
(1, 1, 0),
(1, 1, 1),
];
par_iter!(grid.inner_table()).for_each(|(curr_cell, curr_particles)| {
for &val in neighbours.iter() {
#[cfg(feature = "dim2")]
let neighbor_cell = {
let (i, j) = val;
curr_cell + Vector::new(i, j)
};
#[cfg(feature = "dim3")]
let neighbor_cell = {
let (i, j, k) = val;
curr_cell + Vector::new(i, j, k)
};
if let Some(neighbor_particles) = grid.cell(&neighbor_cell) {
compute_contacts_for_pair_of_cells(
h,
fluids,
boundaries,
fluid_fluid_contacts,
fluid_boundary_contacts,
boundary_boundary_contacts,
curr_cell,
curr_particles,
&neighbor_cell,
neighbor_particles,
);
}
}
});
counters.cd.neighborhood_search_time.pause();
}
fn compute_contacts_for_pair_of_cells(
h: Real,
fluids: &[Fluid],
boundaries: &[Boundary],
fluid_fluid_contacts: &[ParticlesContacts],
fluid_boundary_contacts: &[ParticlesContacts],
boundary_boundary_contacts: &[ParticlesContacts],
curr_cell: &Point<i64>,
curr_particles: &[HGridEntry],
neighbor_cell: &Point<i64>,
neighbor_particles: &[HGridEntry],
) {
for entry in curr_particles {
match entry {
HGridEntry::BoundaryParticle(boundary_i, particle_i) => {
for entry in neighbor_particles {
// NOTE: we are not interested by boundary-fluid contacts.
// Those will already be detected as fluid-boundary contacts instead.
match entry {
HGridEntry::BoundaryParticle(boundary_j, particle_j) => {
let pi = &boundaries[*boundary_i].positions[*particle_i];
let pj = &boundaries[*boundary_j].positions[*particle_j];
if na::distance_squared(pi, pj) <= h * h {
let contact = Contact {
i_model: *boundary_i,
j_model: *boundary_j,
i: *particle_i,
j: *particle_j,
weight: na::zero::<Real>(),
gradient: Vector::zeros(),
};
boundary_boundary_contacts[*boundary_i].contacts[*particle_i]
.write()
.unwrap()
.push(contact);
if *curr_cell != *neighbor_cell {
boundary_boundary_contacts[*boundary_j].contacts[*particle_j]
.write()
.unwrap()
.push(contact.flip());
}
}
}
HGridEntry::FluidParticle(fluid_j, particle_j) => {
if *curr_cell == *neighbor_cell {
// This pair will already be handled by the case where particle_i is a
// fluid particle.
continue;
}
let pi = &boundaries[*boundary_i].positions[*particle_i];
let pj = &fluids[*fluid_j].positions[*particle_j];
if na::distance_squared(pi, pj) <= h * h {
let contact = Contact {
i_model: *fluid_j,
j_model: *boundary_i,
i: *particle_j,
j: *particle_i,
weight: na::zero::<Real>(),
gradient: Vector::zeros(),
};
fluid_boundary_contacts[*fluid_j].contacts[*particle_j]
.write()
.unwrap()
.push(contact);
}
}
}
}
}
HGridEntry::FluidParticle(fluid_i, particle_i) => {
for entry in neighbor_particles {
let (fluid_j, particle_j, is_boundary_j) = entry.into_tuple();
let pi = fluids[*fluid_i].positions[*particle_i];
let pj = if is_boundary_j {
boundaries[fluid_j].positions[particle_j]
} else {
fluids[fluid_j].positions[particle_j]
};
if na::distance_squared(&pi, &pj) <= h * h {
assert!(na::distance_squared(&pj, &pi) <= h * h);
let contact = Contact {
i_model: *fluid_i,
j_model: fluid_j,
i: *particle_i,
j: particle_j,
weight: na::zero::<Real>(),
gradient: Vector::zeros(),
};
if is_boundary_j {
fluid_boundary_contacts[*fluid_i].contacts[*particle_i]
.write()
.unwrap()
.push(contact);
} else {
fluid_fluid_contacts[*fluid_i].contacts[*particle_i]
.write()
.unwrap()
.push(contact);
if *curr_cell != *neighbor_cell {
fluid_fluid_contacts[fluid_j].contacts[particle_j]
.write()
.unwrap()
.push(contact.flip());
}
}
}
}
}
}
}
}
/// Compute all the contacts between the particles of a single fluid object.
pub fn compute_self_contacts(h: Real, fluid: &Fluid, contacts: &mut ParticlesContacts) {
contacts
.contacts
.iter_mut()
.for_each(|c| c.write().unwrap().clear());
contacts
.contacts
.resize_with(fluid.num_particles(), || RwLock::new(Vec::new()));
let mut grid = HGrid::new(h);
for (i, particle) in fluid.positions.iter().enumerate() {
grid.insert(particle, i);
}
for (cell, curr_particles) in grid.cells() {
let neighbors: Vec<_> = grid.neighbor_cells(cell, h).collect();
for particle_i in curr_particles {
for (_, nbh_particles) in &neighbors {
for particle_j in *nbh_particles {
let pi = fluid.positions[*particle_i];
let pj = fluid.positions[*particle_j];
if na::distance_squared(&pi, &pj) <= h * h {
let contact = Contact {
i_model: 0,
j_model: 0,
i: *particle_i,
j: *particle_j,
weight: na::zero::<Real>(),
gradient: Vector::zeros(),
};
contacts.contacts[*particle_i]
.write()
.unwrap()
.push(contact);
}
}
}
}
}
}