Cpt.Captain
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Fluid
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  1. 2
      .gitignore
  2. 1360
      Cargo.lock
  3. 10
      Cargo.toml
  4. 294
      src/fluid.rs
  5. 120
      src/main.rs

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.gitignore vendored
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/target
**/*.rs.bk

1360
Cargo.lock generated
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10
Cargo.toml
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[package]
name = "fluid"
version = "0.1.0"
authors = ["Cpt. Captain <nilskoch94@gmail.com>"]
edition = "2018"
[dependencies]
piston = "0.42.0"
piston_window = "0.89.0"
piston2d-gfx_graphics = "0.56.0"

294
src/fluid.rs
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pub struct FluidSquare {
size: i32,
dt: f32,
diff: f32,
visc: f32,
s: Vec<f32>,
pub density: Vec<f32>,
pub v_x: Vec<f32>,
pub v_y: Vec<f32>,
v_x0: Vec<f32>,
v_y0: Vec<f32>,
}
impl FluidSquare {
pub fn new(size: i32, diff: f32, visc: f32, dt: f32) -> FluidSquare {
FluidSquare {
size: size,
dt: dt,
diff: diff,
visc: visc,
s: vec![0.0; (size * size) as usize],
density: vec![0.0; (size * size) as usize],
v_x: vec![0.0; (size * size) as usize],
v_y: vec![0.0; (size * size) as usize],
v_x0: vec![0.0; (size * size) as usize],
v_y0: vec![0.0; (size * size) as usize],
}
}
pub fn step(&mut self, iter: i32) {
diffuse(
1,
&mut self.v_x0,
&mut self.v_x,
self.visc,
self.dt,
iter,
self.size,
);
diffuse(
2,
&mut self.v_y0,
&mut self.v_y,
self.visc,
self.dt,
iter,
self.size,
);
project(
&mut self.v_x0,
&mut self.v_y0,
&mut self.v_x,
&mut self.v_y,
iter,
self.size,
);
advect(
1,
&mut self.v_x,
&self.v_x0,
&self.v_x0,
&self.v_y0,
self.dt,
self.size,
);
advect(
2,
&mut self.v_y,
&self.v_y0,
&self.v_x0,
&self.v_y0,
self.dt,
self.size,
);
project(
&mut self.v_x,
&mut self.v_y,
&mut self.v_x0,
&mut self.v_y0,
iter,
self.size,
);
diffuse(
0,
&mut self.s,
&mut self.density,
self.diff,
self.dt,
iter,
self.size,
);
advect(
0,
&mut self.density,
&self.s,
&self.v_x,
&self.v_y,
self.dt,
self.size,
);
}
pub fn add_dye(&mut self, x: i32, y: i32, amount: f32) {
let index = ix(x, y, self.size);
self.density[index as usize] += amount;
}
pub fn add_velocity(&mut self, x: i32, y: i32, amount_x: f32, amount_y: f32) {
let index = ix(x, y, self.size);
self.v_x[index as usize] += amount_x;
self.v_y[index as usize] += amount_y;
}
}
fn diffuse(b: i32, x: &mut Vec<f32>, x0: &Vec<f32>, diff: f32, dt: f32, iter: i32, size: i32) {
let a: f32 = dt * diff * (size - 2) as f32 * (size - 2) as f32;
lin_solve(b, x, x0, a, 1.0 + 6.0 * a, iter, size)
}
fn lin_solve(b: i32, x: &mut Vec<f32>, x0: &Vec<f32>, a: f32, c: f32, iter: i32, size: i32) {
let c_recip = 1.0 / c;
for _k in 0..iter {
for j in 1..size - 1 {
for i in 1..size - 1 {
x[ix(i, j, size) as usize] = (x0[ix(i, j, size) as usize]
+ a * (x[ix(i + 1, j, size) as usize]
+ x[ix(i - 1, j, size) as usize]
+ x[ix(i, j + 1, size) as usize]
+ x[ix(i, j - 1, size) as usize]))
* c_recip;
}
}
}
set_bnd(b, x, size);
}
fn set_bnd(b: i32, x: &mut Vec<f32>, size: i32) {
for i in 1..size - 1 {
x[ix(i, 0, size) as usize] = if b == 2 {
-x[ix(i, 1, size) as usize]
} else {
x[ix(i, 1, size) as usize]
};
x[ix(i, size - 1, size) as usize] = if b == 2 {
-x[ix(i, size - 2, size) as usize]
} else {
x[ix(i, size - 2, size) as usize]
};
}
for j in 1..size - 1 {
x[ix(0, j, size) as usize] = if b == 1 {
-x[ix(1, j, size) as usize]
} else {
x[ix(1, j, size) as usize]
};
x[ix(size - 1, j, size) as usize] = if b == 1 {
-x[ix(size - 2, j, size) as usize]
} else {
x[ix(size - 2, j, size) as usize]
};
}
x[ix(0, 0, size) as usize] = 0.5 * (x[ix(1, 0, size) as usize] + x[ix(0, 1, size) as usize]);
x[ix(0, size - 1, size) as usize] =
0.5 * (x[ix(1, size - 1, size) as usize] + x[ix(0, size - 2, size) as usize]);
x[ix(size - 1, 0, size) as usize] =
0.5 * (x[ix(size - 2, 0, size) as usize] + x[ix(size - 1, 1, size) as usize]);
x[ix(size - 1, size - 1, size) as usize] =
0.5 * (x[ix(size - 2, size - 1, size) as usize] + x[ix(size - 1, size - 2, size) as usize]);
}
fn project(
v_x: &mut Vec<f32>,
v_y: &mut Vec<f32>,
p: &mut Vec<f32>,
div: &mut Vec<f32>,
iter: i32,
size: i32,
) {
for j in 1..size - 1 {
for i in 1..size - 1 {
div[ix(i, j, size) as usize] = -0.5
* (v_x[ix(i + 1, j, size) as usize] - v_x[ix(i - 1, j, size) as usize]
+ v_y[ix(i, j + 1, size) as usize]
- v_y[ix(i, j - 1, size) as usize])
/ size as f32;
p[ix(i, j, size) as usize] = 0.0;
}
}
set_bnd(0, div, size);
set_bnd(0, p, size);
lin_solve(0, p, div, 1.0, 6.0, iter, size);
for j in 1..size - 1 {
for i in 1..size - 1 {
v_x[ix(i, j, size) as usize] -= 0.5
* (p[ix(i + 1, j, size) as usize] - p[ix(i - 1, j, size) as usize])
* size as f32;
v_y[ix(i, j, size) as usize] -= 0.5
* (p[ix(i, j + 1, size) as usize] - p[ix(i, j - 1, size) as usize])
* size as f32;
}
}
set_bnd(1, v_x, size);
set_bnd(2, v_y, size);
}
fn advect(
b: i32,
d: &mut Vec<f32>,
d0: &Vec<f32>,
v_x: &Vec<f32>,
v_y: &Vec<f32>,
dt: f32,
size: i32,
) {
let (mut i0, mut i1, mut j0, mut j1): (f32, f32, f32, f32);
let dtx: f32 = dt * (size - 2) as f32;
let dty: f32 = dt * (size - 2) as f32;
let (mut s0, mut s1, mut t0, mut t1): (f32, f32, f32, f32);
let (mut tmp1, mut tmp2, mut x, mut y): (f32, f32, f32, f32);
let nfloat: f32 = size as f32;
let (mut ifloat, mut jfloat): (f32, f32);
for i in 1..size - 1 {
ifloat = i as f32;
for j in 1..size - 1 {
jfloat = j as f32;
tmp1 = dtx * v_x[ix(i, j, size) as usize];
tmp2 = dty * v_y[ix(i, j, size) as usize];
x = ifloat - tmp1;
y = jfloat - tmp2;
if x < 0.5 {
x = 0.5
}
if x > nfloat + 0.5 {
x = nfloat + 0.5
}
i0 = x.floor();
i1 = i0 + 1.0;
if y < 0.5 {
y = 0.5
}
if y > nfloat + 0.5 {
y = nfloat + 0.5
}
j0 = y.floor();
j1 = j0 + 1.0;
s1 = x - i0;
s0 = 1.0 - s1;
t1 = y - j0;
t0 = 1.0 - t1;
let i0i: i32 = i0 as i32;
let i1i: i32 = i1 as i32;
let j0i: i32 = j0 as i32;
let j1i: i32 = j1 as i32;
// probably wrong
d[ix(i, j, size) as usize] = s0
* (t0 * d0[ix(i0i, j0i, size) as usize] + t1 * d0[ix(i0i, j1i, size) as usize])
+ s1 * (t0 * d0[ix(i1i, j0i, size) as usize] + t1 * d0[ix(i1i, j1i, size) as usize])
// d[ix(i, j, size) as usize] = s0
// * (t0 * d0[ix(i0i, j0i, size) as usize] + t1 * d0[ix(i0i, j1i, size) as usize])
// + s1 * (t0 * d0[ix(i1i, j0i, size) as usize]
// + t1 * d0[ix(i1i, j1i, size) as usize]);
}
}
set_bnd(b, d, size);
}
pub fn ix(x: i32, y: i32, size: i32) -> i32 {
// (x + (y * size)).max(0).min(size * size - 1)
let r_x = x.max(0).min(size - 1);
let r_y = y.max(0).min(size - 1);
r_x + (r_y * size)
}

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src/main.rs
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/* A Rust implementation of Mike Ash's fluid solver from
* https://mikeash.com/pyblog/fluid-simulation-for-dummies.html
*
* Inspired by The Coding Trains Challenge #132
* https://www.youtube.com/watch?v=alhpH6ECFvQ
*/
extern crate piston_window;
use piston_window::*;
mod fluid;
mod tests;
fn main() {
let size: i32 = 80;
let scale: i32 = 5;
let iter: i32 = 10;
let dye_amount = 1.0;
let diffusion = 0.2;
let viscosity = 0.000000001;
let dt = 0.000001;
let mut fs: fluid::FluidSquare = fluid::FluidSquare::new(size, dt, viscosity, diffusion);
// fs.step(iter);
println!("Hello, world!");
let _background = [0.1, 0.1, 0.1, 1.0];
let mut events = Events::new(EventSettings::new());
let mut dye = false;
let mut vel = false;
let mut vis = true;
let mut prev_x: f64 = 0.0;
let mut prev_y: f64 = 0.0;
let mut window: PistonWindow = WindowSettings::new("Hello Piston!", [(size * scale) as u32; 2])
.exit_on_esc(true)
// .fullscreen(true)
.build()
.unwrap_or_else(|e| panic!("Failed to build PistonWindow: {}", e));
while let Some(e) = events.next(&mut window) {
window.draw_2d(&e, |_c, g| {
fs.step(iter);
clear(_background, g);
// clear(color::BLACK, g);
for i in 0..size {
for j in 0..size {
let x = i as i32 * scale;
let y = j as i32 * scale;
let rectangle = Rectangle::new(color::alpha(if vis {
fs.density[fluid::ix(i, j, size) as usize] // - 0.02,
} else {
0.5 * (fs.v_x[fluid::ix(i, j, size) as usize]
+ fs.v_y[fluid::ix(i, j, size) as usize])
.abs()
}));
// let square = rectangle::square(
// x as f64,
// y as f64,
// scale as f64,
// )
let square =
rectangle::centered([x as f64, y as f64, scale as f64, scale as f64]);
let transform = _c.transform.trans(0.0, 0.0);
rectangle.draw(square, &_c.draw_state, transform, g);
}
}
});
if let Some(p) = e.press_args() {
if p == Button::Mouse(MouseButton::Left) {
dye = true;
vel = true;
}
if p == Button::Mouse(MouseButton::Right) {
vel = true;
}
if p == Button::Keyboard(Key::V) {
vis = !vis;
}
}
if let Some(p) = e.release_args() {
if p == Button::Mouse(MouseButton::Left) {
dye = false;
vel = false;
}
if p == Button::Mouse(MouseButton::Right) {
vel = false;
}
}
if let Some(m) = e.mouse_cursor_args() {
if dye {
fs.add_dye(
// (e[0] as i32 / (scale * scale)) as i32,
// (e[1] as i32 / (scale * scale)) as i32,
(m[0] as i32 / scale) as i32,
(m[1] as i32 / scale) as i32,
dye_amount,
);
}
if vel {
let mut vel_add = 50.0;
if dye {
vel_add = 20.0;
}
fs.add_velocity(
(m[0] as i32 / scale) as i32,
(m[1] as i32 / scale) as i32,
((m[0] - prev_x) * vel_add) as f32,
((m[1] - prev_y) * vel_add) as f32,
);
prev_x = m[0];
prev_y = m[1];
}
}
}
}
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