7989cb2650
# Objective - Make `Time` API more consistent. - Support time accel/decel/pause. ## Solution This is just the `Time` half of #3002. I was told that part isn't controversial. - Give the "delta time" and "total elapsed time" methods `f32`, `f64`, and `Duration` variants with consistent naming. - Implement accelerating / decelerating the passage of time. - Implement stopping time. --- ## Changelog - Changed `time_since_startup` to `elapsed` because `time.time_*` is just silly. - Added `relative_speed` and `set_relative_speed` methods. - Added `is_paused`, `pause`, `unpause` , and methods. (I'd prefer `resume`, but `unpause` matches `Timer` API.) - Added `raw_*` variants of the "delta time" and "total elapsed time" methods. - Added `first_update` method because there's a non-zero duration between startup and the first update. ## Migration Guide - `time.time_since_startup()` -> `time.elapsed()` - `time.seconds_since_startup()` -> `time.elapsed_seconds_f64()` - `time.seconds_since_startup_wrapped_f32()` -> `time.elapsed_seconds_wrapped()` If you aren't sure which to use, most systems should continue to use "scaled" time (e.g. `time.delta_seconds()`). The realtime "unscaled" time measurements (e.g. `time.raw_delta_seconds()`) are mostly for debugging and profiling.
61 lines
1.8 KiB
Rust
61 lines
1.8 KiB
Rust
//! Shows how to create systems that run every fixed timestep, rather than every tick.
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use bevy::{
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prelude::*,
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time::{FixedTimestep, FixedTimesteps},
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};
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const LABEL: &str = "my_fixed_timestep";
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#[derive(Debug, Hash, PartialEq, Eq, Clone, StageLabel)]
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struct FixedUpdateStage;
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fn main() {
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App::new()
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.add_plugins(DefaultPlugins)
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// this system will run once every update (it should match your screen's refresh rate)
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.add_system(frame_update)
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// add a new stage that runs twice a second
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.add_stage_after(
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CoreStage::Update,
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FixedUpdateStage,
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SystemStage::parallel()
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.with_run_criteria(
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FixedTimestep::step(0.5)
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// labels are optional. they provide a way to access the current
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// FixedTimestep state from within a system
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.with_label(LABEL),
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)
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.with_system(fixed_update),
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)
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.run();
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}
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fn frame_update(mut last_time: Local<f32>, time: Res<Time>) {
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info!(
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"time since last frame_update: {}",
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time.raw_elapsed_seconds() - *last_time
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);
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*last_time = time.raw_elapsed_seconds();
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}
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fn fixed_update(mut last_time: Local<f32>, time: Res<Time>, fixed_timesteps: Res<FixedTimesteps>) {
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info!(
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"time since last fixed_update: {}\n",
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time.raw_elapsed_seconds() - *last_time
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);
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let state = fixed_timesteps.get(LABEL).unwrap();
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info!("fixed timestep: {}\n", 0.5);
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info!(
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"time accrued toward next fixed_update: {}\n",
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state.accumulator()
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);
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info!(
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"time accrued toward next fixed_update (% of timestep): {}",
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state.overstep_percentage()
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);
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*last_time = time.raw_elapsed_seconds();
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}
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