1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
|
use std::f32::consts::{FRAC_PI_2};
use sdl2::rect::Point;
use sdl2::render::Canvas;
pub struct Boid {
dir_x: f32,
dir_y: f32,
position: Point,
}
const TRIANGLE_SIZE: i32 = 20;
const SPEED: f32 = 10.0;
use sdl2::video::Window;
impl Boid {
pub fn new(position: Point) -> Boid {
Boid { dir_x: 0.1, dir_y: 0.2, position }
}
pub fn draw(&self, canvas: &mut Canvas<Window>) {
let top = self.position.offset(0, -TRIANGLE_SIZE);
let bot_left = self.position.offset(-TRIANGLE_SIZE / 3, TRIANGLE_SIZE / 2);
let bot_right = self.position.offset(TRIANGLE_SIZE / 3, TRIANGLE_SIZE / 2);
// direction angle = t
// tan t = y / x
// rotation
// | x cos t -y sin t |
// | x sin t y cos t |
let angle = (self.dir_y / self.dir_x).atan() + FRAC_PI_2;
let s = angle.sin();
let c = angle.cos();
let ps: Vec<Point> = [top, bot_left, bot_right, top].iter().map(|p| {
let x = (p.x() - self.position.x()) as f32;
let y = (p.y() - self.position.y()) as f32;
Point::new((x * c - y * s) as i32 + self.position.x(),
(x * s + y * c) as i32 + self.position.y())
}).collect();
canvas.draw_lines(&ps[..]).unwrap();
}
pub fn step(&mut self) {
self.position = self.position.offset(
(self.dir_x * SPEED) as i32,
(self.dir_y * SPEED) as i32
);
}
}
|
