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Merge pull request #1581 from switch87/fix/1578-arc-warp-aspect 

Warp › Arc: bend in the object's real proportions
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BFlat 2026-10-13 11:27:17 +07:00 committed by GitHub
parent a20b0308b8 a169693817
commit e518974913
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2 changed files with 41 additions and 10 deletions
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47
crates/doc/src/live.rs
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@ -318,8 +318,10 @@ impl WarpStyle {
}
}
/// The warp map on normalised coordinates: `b` = bend (-1..1), `dh`/`dv` = distortion (-1..1).
pub fn warp_point(style: WarpStyle, b: f64, dh: f64, dv: f64, x: f64, y: f64) -> (f64, f64) {
/// The warp map on normalised coordinates: `b` = bend (-1..1), `dh`/`dv` = distortion (-1..1);
/// `aspect` is the box's half-height over its half-width along the warp (Arc bends in real
/// proportions).
pub fn warp_point(style: WarpStyle, b: f64, dh: f64, dv: f64, aspect: f64, x: f64, y: f64) -> (f64, f64) {
use WarpStyle::*;
let t = (y + 1.0) / 2.0; // 0 at top, 1 at bottom
let par = 1.0 - x * x; // parabola: 1 at centre, 0 at sides
@ -328,14 +330,18 @@ pub fn warp_point(style: WarpStyle, b: f64, dh: f64, dv: f64, x: f64, y: f64) ->
if b.abs() < 1e-6 {
(x, y)
} else {
// Bend the centre line into a circular arc of equal length (sweep = |b|·180°).
// Bend the centre line into a circular arc of equal length (sweep = |b|·180°), in
// the box's real proportions (lengths in half-widths, so y counts `aspect` each):
// the edges are concentric arcs, and one that would pass the centre stops there
// instead of folding over (#1578).
let k = if aspect.is_finite() && aspect > 0.0 { aspect } else { 1.0 };
let sweep = b.abs() * PI;
let r0 = 2.0 / sweep;
let yy = if b > 0.0 { y } else { -y };
let yy = if b > 0.0 { y } else { -y } * k;
let a = x / r0;
let r = r0 - yy;
let r = (r0 - yy).max(0.0);
let (s, c) = a.sin_cos();
let (nx, ny) = (r * s, r0 - r * c);
let (nx, ny) = (r * s, (r0 - r * c) / k);
(nx, if b > 0.0 { ny } else { -ny })
}
}
@ -1122,9 +1128,9 @@ fn surface_of<'a>(kind: &'a EnvelopeKind, src: Rect, frame: Affine) -> Box<dyn F
Box::new(move |u: f64, v: f64| {
let (x, y) = (2.0 * u - 1.0, 2.0 * v - 1.0);
let (x2, y2) = if horizontal {
warp_point(st, b, dh, dv, x, y)
warp_point(st, b, dh, dv, hh / hw.max(1e-9), x, y)
} else {
let (a, b2) = warp_point(st, b, dh, dv, y, x);
let (a, b2) = warp_point(st, b, dh, dv, hw / hh.max(1e-9), y, x);
(b2, a)
};
frame * Point::new(c.x + x2 * hw, c.y + y2 * hh)
@ -1711,6 +1717,31 @@ pub(crate) fn max_outset(nodes: &[Arc<Node>]) -> f64 {
#[cfg(test)]
mod tests {
use super::*;
/// #1578: Arc bends in the box's real proportions. In half-width units (y scaled by the
/// aspect), the top and bottom edges are concentric circles about the bend's centre, at their
/// real distance from the centre line; an inner edge that would pass the centre stops there.
#[test]
fn arc_warp_is_round_in_real_proportions() {
for (aspect, b) in [(0.25, 0.1), (0.25, 0.5), (0.25, 1.0), (1.0, 0.5), (2.0, 0.3)] {
let r0 = 2.0 / (b * PI);
for (y, r) in [(-1.0, r0 + aspect), (1.0, (r0 - aspect).max(0.0))] {
for i in 0..=10 {
let x = -1.0 + 0.2 * f64::from(i);
let (nx, ny) = warp_point(WarpStyle::Arc, b, 0.0, 0.0, aspect, x, y);
let d = nx.hypot(ny * aspect - r0);
assert!((d - r).abs() < 1e-9, "aspect {aspect}, bend {b}, y {y}, x {x}: {d} vs {r}");
}
}
}
// At 100 % on a square the inner edge meets at the centre instead of folding over.
let (nx, _) = warp_point(WarpStyle::Arc, 1.0, 0.0, 0.0, 1.0, 0.8, 1.0);
assert!(nx.abs() < 1e-12);
// A square bent less than that is what it always was.
let (nx, ny) = warp_point(WarpStyle::Arc, 0.5, 0.0, 0.0, 1.0, 0.5, 0.25);
let (r0, a) = (4.0 / PI, 0.5 / (4.0 / PI));
assert!((nx - (r0 - 0.25) * a.sin()).abs() < 1e-12 && (ny - (r0 - (r0 - 0.25) * a.cos())).abs() < 1e-12);
}
use vectorcraft_geom::shapes;
fn rect_node(x: f64, y: f64, w: f64, h: f64, c: Color) -> Arc<Node> {

4
crates/effects/src/warp.rs
View File

@ -22,10 +22,10 @@ pub fn warp(path: &PathData, b: Rect, style: WarpStyle, p: &Value) -> PathData {
let f = |q: Point| {
let (x, y) = ((q.x - c.x) / hw, (q.y - c.y) / hh);
let (x2, y2) = if vertical {
let (a, b2) = warp_point(style, bend, dh, dv, y, x);
let (a, b2) = warp_point(style, bend, dh, dv, hw / hh, y, x);
(b2, a)
} else {
warp_point(style, bend, dh, dv, x, y)
warp_point(style, bend, dh, dv, hh / hw, x, y)
};
Point::new(c.x + x2 * hw, c.y + y2 * hh)
};