78 lines
1.8 KiB
Rust
78 lines
1.8 KiB
Rust
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use crate::body::Body;
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const G: f64 = 6.67430e-11;
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pub struct Simulator {
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pub bodies: Vec<Body>,
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pub time: f64,
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pub timestep: f64,
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}
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pub fn distance_squared(a: [f64; 2], b: [f64; 2]) -> f64 {
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let dx = a[0] - b[0];
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let dy = a[1] - b[1];
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dx * dx + dy * dy
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}
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impl Simulator {
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pub fn new(timestep: f64) -> Self {
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Self {
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bodies: Vec::new(),
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time: 0.0,
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timestep,
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}
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}
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pub fn add_body(&mut self, body: Body) {
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self.bodies.push(body);
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}
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pub fn step(&mut self) {
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let n = self.bodies.len();
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let dt = self.timestep;
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let mut accelerations = vec![[0.0, 0.0]; n];
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for i in 0..n {
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for j in 0..n {
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if i == j {
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continue;
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}
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let (bi, bj) = (&self.bodies[i], &self.bodies[j]);
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let dx = bj.position[0] - bi.position[0];
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let dy = bj.position[1] - bi.position[1];
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let dist_sq = distance_squared(bi.position, bj.position);
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let dist = dist_sq.sqrt();
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if dist < 1e-3 {
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continue;
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}
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let force = G * bi.mass * bj.mass / dist_sq;
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let accel = force / bi.mass;
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let ax = accel * dx / dist;
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let ay = accel * dy / dist;
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accelerations[i][0] += ax;
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accelerations[i][1] += ay;
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}
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}
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for i in 0..n {
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let a = accelerations[i];
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let body = &mut self.bodies[i];
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body.velocity[0] += a[0] * dt;
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body.velocity[1] += a[1] * dt;
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body.position[0] += body.velocity[0] * dt;
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body.position[1] += body.velocity[1] * dt;
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}
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self.time += dt;
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}
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}
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