OXYGENHUB
# f993f792537e oxygenhub / crates / backdrop / src / adrift.rs
4.1 KiB · Rust · last changed feat(web): every scene as dense as the sky: knots, fuller streams, 1.4x (refs #167) 23 days ago source blame history raw
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//! Adrift (docs/backgrounds.md §2): the not-found and server-error pages.
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//! A quiet cluster in the margin, and one mark drifting away from it, as
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//! the page drifted from what was asked for. It drifts for a minute, fades
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//! and sets out again. No data.
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use crate::field::{knot, margins, unit, Dot, Field, Orbit, ZOOM};
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use crate::scene::Scene;
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use crate::sky::{hash, Colours};
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const CLUSTER: usize = 160;
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/// The lost mark's speed, and how long one drift lasts, fade included.
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const DRIFT_SPEED: f32 = 7.0;
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const DRIFT_S: f32 = 70.0;
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const FADE_S: f32 = 5.0;
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pub struct Adrift {
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    field: Field,
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    orbits: Vec<Orbit>,
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    centre: (f32, f32),
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    w: f32,
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    h: f32,
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    t: f32,
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}
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impl Adrift {
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    pub fn new(still: bool) -> Adrift {
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        let mut field = Field::new(still);
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        let orbits = knot("adrift", CLUSTER);
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        for k in 0..CLUSTER {
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            let h = hash(&format!("adrift@{k}"));
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            let mut d = Dot::new(0.0, 0.0, 2.0 * ZOOM, if k % 7 == 0 { 2.0 } else { 0.0 });
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            d.bright = 0.5 + 0.5 * unit(h, 48);
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            d.group = 0;
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            d.order = k as u32;
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            field.dots.push(d);
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        }
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        // The cluster's core, and the lost mark, a little larger.
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        field.dots.push(Dot::new(0.0, 0.0, 8.0, 4.0));
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        let mut lost = Dot::new(0.0, 0.0, 3.4 * ZOOM, 0.0);
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        lost.bright = 1.0;
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        field.dots.push(lost);
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        let mut a = Adrift { field, orbits, centre: (0.0, 0.0), w: 0.0, h: 0.0, t: 12.0 };
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        a.place();
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        a
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    }
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    fn place(&mut self) {
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        let (cx, cy) = self.centre;
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        for (i, o) in self.orbits.iter().enumerate() {
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            let (x, y) = o.at((cx, cy), self.t);
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            self.field.dots[i].x = x;
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            self.field.dots[i].y = y;
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        }
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        let core = &mut self.field.dots[CLUSTER];
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        core.x = cx;
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        core.y = cy;
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        // The lost mark leaves up and to the right, fading at the end of
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        // each drift and setting out again from the cluster's edge.
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        let p = self.t % DRIFT_S;
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        let dir: f32 = -0.35;
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        let from = self.orbits.iter().map(|o| o.radius).fold(0.0, f32::max) + 14.0;
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        let lost = &mut self.field.dots[CLUSTER + 1];
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        lost.x = cx + dir.cos() * (from + p * DRIFT_SPEED);
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        lost.y = cy + dir.sin() * (from + p * DRIFT_SPEED);
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        lost.bright = ((DRIFT_S - p) / FADE_S).min(p / FADE_S).clamp(0.0, 1.0);
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    }
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}
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impl Scene for Adrift {
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    fn resize(&mut self, w: f32, h: f32, avoid: Option<(f32, f32)>) {
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        self.w = w;
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        self.h = h;
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        self.centre = match margins(w, avoid) {
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            Some((l, _)) => (l * 0.45, h * 0.62),
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            None => (w * 0.15, h * 0.7),
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        };
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        self.place();
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    }
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    fn point(&mut self, at: Option<(f32, f32)>) {
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        self.field.point(at);
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    }
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    fn step(&mut self, dt: f32) {
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        if !self.field.still {
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            self.t += dt.clamp(0.0, 0.1);
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        }
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        self.place();
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        self.field.light(dt);
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    }
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    fn instances(&self, c: &Colours, out: &mut Vec<f32>) {
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        self.field.instances(c, out)
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    }
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    fn links(&self, c: &Colours, out: &mut Vec<f32>) {
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        self.field.links(c, out)
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    }
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    fn label(&self) -> Option<(&str, f32, f32)> {
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        None
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    }
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    fn busy(&self) -> bool {
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        !self.field.still || self.field.easing()
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    }
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    fn still(&self) -> bool {
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        self.field.still
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    }
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    fn size(&self) -> (f32, f32) {
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        (self.w, self.h)
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    }
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}
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#[cfg(test)]
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mod tests {
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    use super::*;
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    #[test]
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    fn one_mark_drifts_away_from_the_cluster_and_sets_out_again() {
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        let mut a = Adrift::new(false);
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        a.resize(2560.0, 1270.0, Some((707.0, 1838.0)));
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        assert!(a.centre.0 < 707.0, "the cluster sits in the margin");
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        let dist = |a: &Adrift| {
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            let l = &a.field.dots[CLUSTER + 1];
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            (l.x - a.centre.0).hypot(l.y - a.centre.1)
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        };
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        let early = dist(&a);
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        for _ in 0..200 {
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            a.step(0.1);
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        }
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        assert!(dist(&a) > early + 100.0, "it drifts away");
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        for _ in 0..500 {
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            a.step(0.1);
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        }
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        assert!(dist(&a) < early + 100.0, "and sets out again");
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    }
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}