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// #![feature(alloc_system, global_allocator, allocator_api)]
// extern crate alloc_system;
// use alloc_system::System;
// #[global_allocator]
// static A: System = System;
extern crate graphics;
extern crate piston_window;
extern crate rand;
use graphics::math::{ Vec2d, add, mul_scalar };
use piston_window::{ PistonWindow, WindowSettings, clear, rectangle };
use rand::distributions::{IndependentSample, Range};
type RGBA = [f32; 4];
const WHITE: RGBA = [1.0; 4];
const GRAY: RGBA = [0.7, 0.7, 0.7, 0.3];
const N_PARTICLES: usize = 500;
struct World {
current_turn: usize,
shapes: Vec<Box<Shape>>,
height: u32,
width: u32,
}
struct Shape {
height: f64,
width: f64,
position: Vec2d<f64>,
velocity: Vec2d<f64>,
acceleration: Vec2d<f64>,
color: RGBA,
}
impl Shape {
fn new(x: f64, y: f64) -> Self {
let mut rng = rand::thread_rng();
let legal_range = Range::new(-5_f64, 5_f64);
let x_speed = legal_range.ind_sample(&mut rng);
let y_speed = legal_range.ind_sample(&mut rng);
let x_accel = 0.1 * legal_range.ind_sample(&mut rng);
let y_accel = 0.1 * legal_range.ind_sample(&mut rng);
Shape {
height: 10.0,
width: 10.0,
position: [x, y],
velocity: [x_speed, y_speed],
acceleration: [x_accel, y_accel],
color: GRAY,
}
}
fn update(&mut self) {
self.velocity = add(self.velocity, self.acceleration); // <> There is no matrix/vector math operators within the language. `graphics::math` is providing this functionality for us.
self.position = add(self.position, self.velocity);
self.acceleration = mul_scalar(self.acceleration, 0.7); // <> Slow down the shape's movement
self.color[3] *= 0.97;
}
}
impl World {
fn new(width: u32, height: u32) -> World {
World {
current_turn: 0,
shapes: Vec::<Box<Shape>>::new(),
height: height,
width: width,
}
}
fn add_shapes(&mut self, n: usize) {
let x = (self.width / 2) as f64;
let y = (self.height / 2) as f64;
for _ in 0..n {
self.shapes.push(Box::new(Shape::new(x, y)));
};
}
fn remove_shapes(&mut self, n: usize) {
let n_shapes = self.shapes.len();
let to_remove = if n > n_shapes {
n_shapes
} else {
n
};
// let to_remove = cmp::min(n as usize, self.shapes.len());
for _ in 0..to_remove {
self.shapes.remove(0); // Remove the oldest particle. This is quite an inefficient operation, as all remaining particles are shifted to fill the now-empty slot. A smarter strategy would be to use `std::collections::VecDeque`, which supports removing from the front.
}
self.shapes.shrink_to_fit(); // Will help to force a re-allocation later when shapes are added.
}
fn calc_population_change(&self) -> isize {
const N: f64 = N_PARTICLES as f64; // <> Shorter alias
const MAX: f64 = N*0.5;
const MIN: f64 = -N*0.5;
let x: f64 = self.current_turn as f64;
//let n: f64 = N_PARTICLES;
let n = 0.4*N*(0.1*x).sin() + 0.1*N*x.sin();
n.max(MIN).min(MAX).round() as isize // limit range of growth/death then convert to `isize`
}
fn update(&mut self) {
let n = self.calc_population_change();
//let n = as usize; // <> Convert f64 to usize
if n > 0 {
self.add_shapes(n as usize);
} else {
self.remove_shapes(n.abs() as usize);
}
self.current_turn += 1;
}
}
// impl Iterator for World {
// type Item = isize;
// fn next(&mut self) -> Option<isize> {
// let x = self.current_turn;
// // 30sin(x) + 10sin(0.1x) + 20sin(0.2x) + 30sin(0.3x) + 40sin(0.4x) + 50sin(0.5x)
// let y = 50.0*(0.1*x).sin() + 30.0*x.sin();
// self.current_turn += 1.0;
// Some(y.round() as isize)
// }
// }
fn main() {
let (width, height) = (640, 480);
let mut window: PistonWindow =
WindowSettings::new("particles", [width, height])
.exit_on_esc(true)
.build()
.expect("Could not create a window.");
// Initialize
let mut world = World::new(width, height);
world.add_shapes(N_PARTICLES);
while let Some(event) = window.next() { // main loop
// Update Step
for shape in &mut world.shapes {
shape.update();
}
world.update();
// Render Step
window.draw_2d(&event, |ctx, renderer| {
clear(WHITE, renderer);
for s in &mut world.shapes {
let rect = [s.position[0], s.position[1], s.width, s.height];
let transformation_matrix = ctx.transform;
rectangle(s.color, rect, transformation_matrix, renderer); // create a graphics::Rectangle and call draw() on it
}
});
}
}
|
