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AI import: a gradient mesh patch's edges bend through the anchors listed between its corners
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
This commit is contained in:
EricKuck
committed by
bflatastic
bflatastic
co-authored by
Claude Opus 5.5
Claude Opus 5.5
parent
e93ba4c83f
commit
1682d59b65
@@ -3,7 +3,12 @@
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//! the origin round to the one beside it), ended by `/E` — and `/End X!`.
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//!
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//! A corner is `[colour… opacity x y` then the handle towards the next corner, a weight, the handle
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//! towards the previous one and a weight `]`, in art space. Each patch becomes a 1×1 mesh.
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//! towards the previous one and a weight `]`, in art space. A patch whose edges bend through more
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//! anchors has them as `[x y` with a handle towards each neighbor and a weight `] /A` or `/S`,
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//! after the corner their edge starts from (before the first corner for the edge back to it), in
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//! the edge's direction (`/A`) or against it (`/S`). A patch with single cubic edges becomes a 1×1
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//! mesh; one with more anchors, the Coons patch of its edges, cut into cells where any edge has an
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//! anchor.
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//!
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//! `X!`/`X#` aren't publicly documented (the AI7 specification predates meshes).
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@@ -20,6 +25,9 @@ const MAX_PATCHES: usize = 4096;
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pub(super) struct MeshReader {
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space: String,
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corners: Vec<Vec<f64>>,
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/// The patch's anchors between its corners (`/A`, `/S`): the edge, whether listed against it, and
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/// a point and its two handles.
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anchors: Vec<(usize, bool, [f64; 6])>,
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pub patches: Vec<GradientMesh>,
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/// Something in it this doesn't read.
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pub unread: bool,
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@@ -42,9 +50,23 @@ impl MeshReader {
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}
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}
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}
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"A" | "S" => {
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if let Some(V::Arr(a)) = value {
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let n: Vec<f64> = a.iter().filter_map(V::num).take(7).collect();
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match n.as_slice() {
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&[x, y, ax, ay, bx, by, ..] if self.anchors.len() < 64 && [x, y, ax, ay, bx, by].iter().all(|v| v.is_finite()) => {
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let p = |x, y| to_doc * Point::new(x, y);
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let (at, a, b) = (p(x, y), p(ax, ay), p(bx, by));
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self.anchors.push(((self.corners.len() + 3) % 4, key == "S", [at.x, at.y, a.x, a.y, b.x, b.y]));
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}
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_ => self.unread = true,
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}
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}
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}
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"E" => {
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let corners = std::mem::take(&mut self.corners);
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match self.patch(&corners, to_doc) {
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let anchors = std::mem::take(&mut self.anchors);
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match self.patch(&corners, &anchors, to_doc) {
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Some(m) if self.patches.len() < MAX_PATCHES => self.patches.push(m),
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_ => self.unread = true,
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}
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@@ -63,7 +85,7 @@ impl MeshReader {
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})
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}
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fn patch(&self, corners: &[Vec<f64>], to_doc: Affine) -> Option<GradientMesh> {
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fn patch(&self, corners: &[Vec<f64>], anchors: &[(usize, bool, [f64; 6])], to_doc: Affine) -> Option<GradientMesh> {
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let [n0, n1, n2, n3] = corners else { return None };
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// (anchor, towards the next corner, towards the previous one, colour, opacity)
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let read = |n: &Vec<f64>| -> Option<(Point, Vec2, Vec2, Color, f32)> {
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@@ -77,6 +99,9 @@ impl MeshReader {
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Some((at, to_doc * Point::new(nx, ny) - at, to_doc * Point::new(px, py) - at, color, opacity.clamp(0.0, 1.0) as f32))
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};
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let (a, b, c, d) = (read(n0)?, read(n1)?, read(n2)?, read(n3)?);
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if !anchors.is_empty() {
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return Some(coons([a, b, c, d], anchors));
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}
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// Rows run from the first corner to the second, columns from the first to the fourth.
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let point = |(p, _, _, color, opacity): (Point, Vec2, Vec2, Color, f32), handles: [(usize, Vec2); 2]| {
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let mut h = [Vec2::ZERO; 4];
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@@ -97,6 +122,143 @@ impl MeshReader {
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}
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}
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type Corner = (Point, Vec2, Vec2, Color, f32);
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type Cubic = [Point; 4];
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/// A patch whose edges bend through more anchors: its edges (first corner → second → third → fourth
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/// → first) as runs of cubics, each anchor on the edge it lies along, and the Coons patch they bound
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/// as a mesh cut wherever an edge has an anchor, so each cell's edges are single cubics again.
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fn coons(corners: [Corner; 4], anchors: &[(usize, bool, [f64; 6])]) -> GradientMesh {
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let runs: Vec<Vec<Cubic>> = (0..4)
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.map(|e| {
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let (p, q) = (&corners[e], &corners[(e + 1) % 4]);
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// Each anchor's first handle points to the one listed before it, so back along the edge
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// for `/A`, forward for `/S`, which lists them against the edge.
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let mut stops: Vec<(Point, Point, Point)> = anchors
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.iter()
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.filter(|(edge, ..)| *edge == e)
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.map(|&(_, against, [x, y, ax, ay, bx, by])| {
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let (at, h1, h2) = (Point::new(x, y), Point::new(ax, ay), Point::new(bx, by));
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if against { (h2, at, h1) } else { (h1, at, h2) }
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})
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.collect();
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if anchors.iter().any(|&(edge, against, _)| edge == e && against) {
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stops.reverse();
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}
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let (mut from, mut out) = (p.0, p.0 + p.1);
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let mut run = vec![];
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for (back, at, ahead) in stops {
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run.push([from, out, back, at]);
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(from, out) = (at, ahead);
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}
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run.push([from, out, q.0 + q.2, q.0]);
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run
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})
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.collect();
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// The patch is over u (first corner → fourth) and v (first → second).
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let [left, bottom, right, top] = [
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Path { run: runs[0].clone(), reversed: false },
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Path { run: runs[1].clone(), reversed: false },
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Path { run: runs[2].clone(), reversed: true },
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Path { run: runs[3].clone(), reversed: true },
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];
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let [ca, cb, cc, cd] = corners.map(|c| c.0.to_vec2());
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let surface = |u: f64, v: f64| -> Vec2 {
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top.at(u) * (1.0 - v) + bottom.at(u) * v + left.at(v) * (1.0 - u) + right.at(v) * u
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- (ca * ((1.0 - u) * (1.0 - v)) + cd * (u * (1.0 - v)) + cb * ((1.0 - u) * v) + cc * (u * v))
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};
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let du = |u: f64, v: f64, after: bool| -> Vec2 {
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top.slope(u, after) * (1.0 - v) + bottom.slope(u, after) * v - left.at(v) + right.at(v) - (cd - ca) * (1.0 - v) - (cc - cb) * v
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};
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let dv = |u: f64, v: f64, after: bool| -> Vec2 {
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left.slope(v, after) * (1.0 - u) + right.slope(v, after) * u - top.at(u) + bottom.at(u) - (cb - ca) * (1.0 - u) - (cc - cd) * u
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};
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let cuts = |a: &Path, b: &Path| {
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let mut c: Vec<f64> = a.cuts().into_iter().chain(b.cuts()).collect();
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c.sort_by(f64::total_cmp);
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c.dedup_by(|x, y| (*x - *y).abs() < 1e-9);
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c
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};
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let (us, vs) = (cuts(&top, &bottom), cuts(&left, &right));
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let (ra, rb, rc, rd) = (&corners[0], &corners[1], &corners[2], &corners[3]);
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let mut points = Vec::with_capacity(us.len() * vs.len());
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for (r, &v) in vs.iter().enumerate() {
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for (c, &u) in us.iter().enumerate() {
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let mut h = [Vec2::ZERO; 4];
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if let Some(&next) = us.get(c + 1) {
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h[H_RIGHT] = du(u, v, true) * ((next - u) / 3.0);
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}
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if let Some(&prev) = c.checked_sub(1).and_then(|i| us.get(i)) {
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h[H_LEFT] = du(u, v, false) * (-(u - prev) / 3.0);
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}
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if let Some(&next) = vs.get(r + 1) {
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h[H_DOWN] = dv(u, v, true) * ((next - v) / 3.0);
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}
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if let Some(&prev) = r.checked_sub(1).and_then(|i| vs.get(i)) {
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h[H_UP] = dv(u, v, false) * (-(v - prev) / 3.0);
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}
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let (u32_, v32) = (u as f32, v as f32);
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let color = mix(&mix(&ra.3, &rd.3, u32_), &mix(&rb.3, &rc.3, u32_), v32);
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let opacity = (ra.4 * (1.0 - u32_) + rd.4 * u32_) * (1.0 - v32) + (rb.4 * (1.0 - u32_) + rc.4 * u32_) * v32;
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points.push(MeshPoint { p: surface(u, v).to_point(), color, opacity, handles: h });
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}
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}
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GradientMesh { rows: (vs.len() - 1) as u32, cols: (us.len() - 1) as u32, points }
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}
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/// An edge as a run of cubics, each taking an equal share of its parameter, read backwards if
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/// `reversed`.
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struct Path {
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run: Vec<Cubic>,
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reversed: bool,
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}
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impl Path {
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fn piece(&self, t: f64, after: bool) -> (usize, f64) {
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let n = self.run.len();
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let t = if self.reversed { 1.0 - t } else { t };
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// At a joint, the piece the moving direction enters.
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let towards_end = after != self.reversed;
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let scaled = t * n as f64;
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let mut i = if towards_end { scaled.floor() } else { scaled.ceil() - 1.0 }.clamp(0.0, (n - 1) as f64) as usize;
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if i >= n {
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i = n - 1;
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}
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(i, scaled - i as f64)
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}
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fn at(&self, t: f64) -> Vec2 {
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let (i, s) = self.piece(t, true);
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let [p0, p1, p2, p3] = self.run[i].map(|p| p.to_vec2());
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let r = 1.0 - s;
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p0 * (r * r * r) + p1 * (3.0 * r * r * s) + p2 * (3.0 * r * s * s) + p3 * (s * s * s)
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}
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/// The derivative along the patch's parameter, from the piece `after` (towards larger `t`) or before.
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fn slope(&self, t: f64, after: bool) -> Vec2 {
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let (i, s) = self.piece(t, after);
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let [p0, p1, p2, p3] = self.run[i].map(|p| p.to_vec2());
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let r = 1.0 - s;
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let d = (p1 - p0) * (3.0 * r * r) + (p2 - p1) * (6.0 * r * s) + (p3 - p2) * (3.0 * s * s);
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let scale = self.run.len() as f64;
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if self.reversed { d * -scale } else { d * scale }
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}
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/// Where its pieces meet, with its ends, in the patch's parameter.
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fn cuts(&self) -> Vec<f64> {
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let n = self.run.len();
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(0..=n).map(|i| i as f64 / n as f64).collect()
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}
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}
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/// `a` towards `b` by `t`, in their own colour model where they share one.
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fn mix(a: &Color, b: &Color, t: f32) -> Color {
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let l = |x: f32, y: f32| x + (y - x) * t;
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match (a, b) {
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(Color::Rgb { r, g, b: bl }, Color::Rgb { r: r2, g: g2, b: b2 }) => Color::rgb(l(*r, *r2), l(*g, *g2), l(*bl, *b2)),
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(Color::Cmyk { c, m, y, k }, Color::Cmyk { c: c2, m: m2, y: y2, k: k2 }) => Color::cmyk(l(*c, *c2), l(*m, *m2), l(*y, *y2), l(*k, *k2)),
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(Color::Gray { k }, Color::Gray { k: k2 }) => Color::gray(l(*k, *k2)),
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_ => a.lerp(b, t),
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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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@@ -113,6 +275,32 @@ mod tests {
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reader.entry(&[V::Num(0.0), V::Name("E".into())], Affine::IDENTITY);
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}
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/// An anchor on a patch's edge (`/A` after the first corner: on the edge from it to the second)
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/// bends the edge through it: the patch is cut there into two cells whose shared corner is the
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/// anchor, with the anchor's handles along the edge.
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#[test]
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fn an_edge_anchor_cuts_its_patch_there() {
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let mut reader = MeshReader { space: "DeviceGray".into(), ..MeshReader::default() };
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let corner = |x: f64, y: f64, next: (f64, f64), prev: (f64, f64)| {
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vec![V::Arr([0.0, 1.0, x, y, next.0, next.1, 1.0, prev.0, prev.1, 1.0].map(V::Num).to_vec()), V::Name("N".into())]
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};
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reader.entry(&corner(0.0, 0.0, (0.0, 2.0), (2.0, 0.0)), Affine::IDENTITY);
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reader.entry(&[V::Arr([-1.0, 5.0, -1.0, 4.0, -1.0, 6.0, 1.0].map(V::Num).to_vec()), V::Name("A".into())], Affine::IDENTITY);
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reader.entry(&corner(0.0, 10.0, (2.0, 10.0), (0.0, 8.0)), Affine::IDENTITY);
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reader.entry(&corner(10.0, 10.0, (10.0, 8.0), (8.0, 10.0)), Affine::IDENTITY);
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reader.entry(&corner(10.0, 0.0, (8.0, 0.0), (10.0, 2.0)), Affine::IDENTITY);
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reader.entry(&[V::Num(0.0), V::Name("E".into())], Affine::IDENTITY);
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assert!(!reader.unread);
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let mesh = &reader.patches[0];
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assert_eq!((mesh.rows, mesh.cols), (2, 1));
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let left = &mesh.points[2];
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assert!((left.p - Point::new(-1.0, 5.0)).hypot() < 1e-9, "{:?}", left.p);
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assert!((left.handles[H_UP] - Vec2::new(0.0, -1.0)).hypot() < 1e-9 && (left.handles[H_DOWN] - Vec2::new(0.0, 1.0)).hypot() < 1e-9);
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// The edge still starts and ends at its corners, with their handles.
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assert!((mesh.points[0].handles[H_DOWN] - Vec2::new(0.0, 2.0)).hypot() < 1e-9);
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assert!((mesh.points[4].p - Point::new(0.0, 10.0)).hypot() < 1e-9);
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}
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#[test]
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fn hostile_meshes_are_capped_and_checked() {
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let mut reader = MeshReader { space: "DeviceGray".into(), ..MeshReader::default() };
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