fixed_timestep/
fixed_timestep.rs

1//! Shows how to create systems that run every fixed timestep, rather than every tick.
2
3use bevy::prelude::*;
4
5fn main() {
6    App::new()
7        .add_plugins(DefaultPlugins)
8        // this system will run once every update (it should match your screen's refresh rate)
9        .add_systems(Update, frame_update)
10        // add our system to the fixed timestep schedule
11        .add_systems(FixedUpdate, fixed_update)
12        // configure our fixed timestep schedule to run twice a second
13        .insert_resource(Time::<Fixed>::from_seconds(0.5))
14        .run();
15}
16
17fn frame_update(mut last_time: Local<f32>, time: Res<Time>) {
18    // Default `Time` is `Time<Virtual>` here
19    info!(
20        "time since last frame_update: {}",
21        time.elapsed_secs() - *last_time
22    );
23    *last_time = time.elapsed_secs();
24}
25
26fn fixed_update(mut last_time: Local<f32>, time: Res<Time>, fixed_time: Res<Time<Fixed>>) {
27    // Default `Time`is `Time<Fixed>` here
28    info!(
29        "time since last fixed_update: {}\n",
30        time.elapsed_secs() - *last_time
31    );
32
33    info!("fixed timestep: {}\n", time.delta_secs());
34    // If we want to see the overstep, we need to access `Time<Fixed>` specifically
35    info!(
36        "time accrued toward next fixed_update: {}\n",
37        fixed_time.overstep().as_secs_f32()
38    );
39    *last_time = time.elapsed_secs();
40}