51 lines
1.5 KiB
Rust
51 lines
1.5 KiB
Rust
use std::time::{Duration, Instant};
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/// A simple linear interpolation calculation function.
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/// p = `percent_complete` in decimal form
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#[must_use]
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pub fn lerp(start: f32, end: f32, p: f32) -> f32 {
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(1.0 - p) * start + p * end
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}
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/// A fast smooth interpolation calculation function.
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/// p = `percent_complete` in decimal form
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#[must_use]
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pub fn slerp(start: f32, end: f32, p: f32) -> f32 {
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let t = smootherstep(p);
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(1.0 - t) * start + t * end
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}
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/// utility function which maps a value [0, 1] -> [0, 1] using the smootherstep function
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pub fn smootherstep(t: f32) -> f32 {
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(6.0 * t.powi(5) - 15.0 * t.powi(4) + 10.0 * t.powi(3)).clamp(0.0, 1.0)
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}
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#[derive(Default, Debug)]
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pub struct State {
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pub last_change: Option<Instant>,
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}
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impl State {
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pub fn changed(&mut self, dur: Duration) {
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let t = self.t(dur, false);
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let diff = dur.mul_f32(t.abs());
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let now = Instant::now();
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self.last_change = Some(now.checked_sub(diff).unwrap_or(now));
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}
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pub fn anim_done(&mut self, dur: Duration) {
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if self
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.last_change
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.is_some_and(|t| Instant::now().duration_since(t) > dur)
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{
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self.last_change = None;
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}
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}
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pub fn t(&self, dur: Duration, forward: bool) -> f32 {
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let res = self.last_change.map_or(1., |t| {
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Instant::now().duration_since(t).as_millis() as f32 / dur.as_millis() as f32
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});
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if forward { res } else { 1. - res }
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}
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}
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