forked from 1b-agent/fieldcraft-upstream
mesh: projection smoother keeps the best sweep grid and lifts from the better start (#489)
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01UhhZMBTviDQxZvwnyP89fo
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jyvikoandClaude Opus 5.5 authored and Irakli Kourtis committed
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+141
-86
@@ -319,6 +319,33 @@ fn mesh_quality(x: &[P], hexes: &[[u32; 8]]) -> Local {
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l
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}
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/// A grid's smallest and mean scaled Jacobian, to pick the best grid the sweeps passed through.
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#[derive(Debug, Clone, Copy)]
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struct SweepScore {
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min: f64,
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mean: f64,
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}
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impl SweepScore {
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/// A larger smallest scaled Jacobian, or the same one (to rounding) with a larger mean.
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fn better_than(self, other: SweepScore) -> bool {
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if (self.min - other.min).abs() > SCORE_TIE { self.min > other.min } else { self.mean > other.mean + SCORE_TIE }
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}
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}
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/// Two smallest scaled Jacobians this close count as equal.
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const SCORE_TIE: f64 = 1e-9;
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fn sweep_score(x: &[P], hexes: &[[u32; 8]]) -> SweepScore {
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let (mut min, mut sum) = (f64::INFINITY, 0.0);
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for hex in hexes {
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let sj = hex_scaled_jacobian(&hex.map(|q| at(x, q)));
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min = min.min(sj);
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sum += sj;
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}
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SweepScore { min, mean: if hexes.is_empty() { 0.0 } else { sum / hexes.len() as f64 } }
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}
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/// Smooth in place: at most `iterations` sweeps, stopping when no node moves more than `tol`.
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///
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/// The sweeps let a move take an element down to [`SWEEP_FLOOR`] (a sheared block straightens
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@@ -403,6 +430,10 @@ fn pass(m: &mut Mesh, g: &dyn Geometry, targets: &[Vec<u32>], method: Smoothing,
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return report;
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}
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let ptol = 1e-3 * tol;
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// The sweeps do not raise the smallest scaled Jacobian monotonically (a move may take an
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// element down to the sweep floor), so where they stop decides the result; keep the best grid
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// seen (smallest scaled Jacobian, then the mean) and lift the worst elements from that.
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let mut best = (sweep_score(m.nodes, hexes), m.nodes.clone());
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for it in 0..iterations {
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report.iterations = it + 1;
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let mut moved = 0.0f64;
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@@ -458,107 +489,131 @@ fn pass(m: &mut Mesh, g: &dyn Geometry, targets: &[Vec<u32>], method: Smoothing,
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}
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}
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}
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let score = sweep_score(m.nodes, hexes);
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if score.better_than(best.0) {
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best = (score, m.nodes.clone());
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}
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if moved <= tol {
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break;
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}
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}
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// The worst elements: each of their nodes searched for the place that raises the smallest
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// scaled Jacobian around it (a compass search, the optimization-based smoothing of L. A.
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// Freitag and C. Ollivier-Gooch, *Tetrahedral mesh improvement using swapping and smoothing*,
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// IJNME 40:3979–4002, 1997, on Knupp's hexahedral metric), boundary nodes kept on their
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// targets.
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for _ in 0..OPTIMIZE_ROUNDS {
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let mut poor: Vec<u32> =
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m.hexes.iter().filter(|h| hex_scaled_jacobian(&h.map(|q| at(m.nodes, q))) < LIFT_BELOW).flat_map(|h| h.iter().copied()).collect();
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poor.sort_unstable();
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poor.dedup();
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if poor.is_empty() {
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break;
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// Where the sweeps stopped and the best grid they passed through each go through the lift
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// and the straightening; the better result is kept (the lift can raise an element the best
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// sweep grid left low, so neither start always wins).
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let end = m.nodes.clone();
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let mut starts = vec![end];
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if best.1 != starts[0] {
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starts.push(best.1);
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}
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let mut finished: Option<(SweepScore, Local, Vec<P>)> = None;
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for start in starts {
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*m.nodes = start;
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// The worst elements: each of their nodes searched for the place that raises the smallest
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// scaled Jacobian around it (a compass search, the optimization-based smoothing of L. A.
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// Freitag and C. Ollivier-Gooch, *Tetrahedral mesh improvement using swapping and smoothing*,
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// IJNME 40:3979–4002, 1997, on Knupp's hexahedral metric), boundary nodes kept on their
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// targets.
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for _ in 0..OPTIMIZE_ROUNDS {
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let mut poor: Vec<u32> =
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m.hexes.iter().filter(|h| hex_scaled_jacobian(&h.map(|q| at(m.nodes, q))) < LIFT_BELOW).flat_map(|h| h.iter().copied()).collect();
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poor.sort_unstable();
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poor.dedup();
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if poor.is_empty() {
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break;
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}
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let mut improved = false;
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for &v in &poor {
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let c = cons(v);
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if matches!(c, Constraint::Corner(..)) {
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continue;
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}
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let p = at(m.nodes, v);
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let reach = edges.get(v as usize).map_or(0.0, |e| e.iter().map(|&w| dist(at(m.nodes, w), p)).fold(f64::INFINITY, f64::min));
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if !(reach > 0.0 && reach.is_finite()) {
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continue;
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}
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let start_quality = quality(m.nodes, v);
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let mut best = (start_quality.sj, p);
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let mut h = 0.25 * reach;
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for _ in 0..6 {
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let start = best.1;
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for dir in COMPASS {
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let x = place(g, targets, c, add(start, scale(dir, h)), ptol);
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if let Some(slot) = m.nodes.get_mut(v as usize) {
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*slot = x;
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}
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let qx = quality(m.nodes, v);
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if qx.sj > best.0 + 1e-9 && qx.keeps(start_quality) {
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best = (qx.sj, x);
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}
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}
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if best.1 == start {
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h *= 0.5;
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}
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}
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if let Some(slot) = m.nodes.get_mut(v as usize) {
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*slot = best.1;
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}
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improved |= best.1 != p;
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}
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if !improved {
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break;
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}
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}
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let mut improved = false;
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for &v in &poor {
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let c = cons(v);
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if matches!(c, Constraint::Corner(..)) {
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continue;
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}
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let p = at(m.nodes, v);
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let reach = edges.get(v as usize).map_or(0.0, |e| e.iter().map(|&w| dist(at(m.nodes, w), p)).fold(f64::INFINITY, f64::min));
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if !(reach > 0.0 && reach.is_finite()) {
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continue;
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}
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let start_quality = quality(m.nodes, v);
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let mut best = (start_quality.sj, p);
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let mut h = 0.25 * reach;
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for _ in 0..6 {
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let start = best.1;
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for dir in COMPASS {
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let x = place(g, targets, c, add(start, scale(dir, h)), ptol);
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// The search moves boundary nodes one at a time, each to its own best place, which leaves the
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// grid lines on a face zigzagging from node to node. Straighten them: each surface node back
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// toward the mean of its neighbours on the surface, as far as no element round it falls below
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// the lower of its own value and the mesh's smallest after the search (so the mesh's worst
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// element is no worse for it).
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let floor = hexes.iter().map(|h| hex_scaled_jacobian(&h.map(|q| at(m.nodes, q)))).fold(f64::INFINITY, f64::min);
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for _ in 0..STRAIGHTEN_SWEEPS {
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let mut moved = false;
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for v in 0..n as u32 {
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let c = cons(v);
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if !matches!(c, Constraint::Surface(_)) {
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continue;
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}
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let p = at(m.nodes, v);
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let Some(q) = along_boundary.get(&v).and_then(|e| {
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let (mut s, mut k) = ([0.0; 3], 0usize);
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for &w in e {
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s = add(s, at(m.nodes, w));
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k += 1;
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}
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(k > 0).then(|| place(g, targets, c, scale(s, 1.0 / k as f64), ptol))
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}) else {
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continue;
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};
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if dist(q, p) <= ptol {
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continue;
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}
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let before = quality(m.nodes, v);
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for step in [1.0, 0.5, 0.25] {
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let x = if step == 1.0 { q } else { place(g, targets, c, add(p, scale(sub(q, p), step)), ptol) };
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if let Some(slot) = m.nodes.get_mut(v as usize) {
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*slot = x;
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}
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let qx = quality(m.nodes, v);
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if qx.sj > best.0 + 1e-9 && qx.keeps(start_quality) {
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best = (qx.sj, x);
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if quality(m.nodes, v).keeps_above(before, floor) {
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moved = true;
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break;
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}
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if let Some(slot) = m.nodes.get_mut(v as usize) {
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*slot = p;
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}
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}
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if best.1 == start {
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h *= 0.5;
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}
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}
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if let Some(slot) = m.nodes.get_mut(v as usize) {
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*slot = best.1;
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if !moved {
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break;
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}
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improved |= best.1 != p;
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}
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if !improved {
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break;
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let (score, local) = (sweep_score(m.nodes, hexes), mesh_quality(m.nodes, hexes));
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let better = finished.as_ref().is_none_or(|(s, l, _)| score.better_than(*s) && local.ratio <= l.ratio.max(EDGE_RATIO_CEILING));
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if better {
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finished = Some((score, local, m.nodes.clone()));
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}
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}
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// The search moves boundary nodes one at a time, each to its own best place, which leaves the
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// grid lines on a face zigzagging from node to node. Straighten them: each surface node back
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// toward the mean of its neighbours on the surface, as far as no element round it falls below
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// the lower of its own value and the mesh's smallest after the search (so the mesh's worst
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// element is no worse for it).
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let floor = hexes.iter().map(|h| hex_scaled_jacobian(&h.map(|q| at(m.nodes, q)))).fold(f64::INFINITY, f64::min);
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for _ in 0..STRAIGHTEN_SWEEPS {
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let mut moved = false;
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for v in 0..n as u32 {
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let c = cons(v);
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if !matches!(c, Constraint::Surface(_)) {
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continue;
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}
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let p = at(m.nodes, v);
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let Some(q) = along_boundary.get(&v).and_then(|e| {
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let (mut s, mut k) = ([0.0; 3], 0usize);
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for &w in e {
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s = add(s, at(m.nodes, w));
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k += 1;
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}
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(k > 0).then(|| place(g, targets, c, scale(s, 1.0 / k as f64), ptol))
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}) else {
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continue;
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};
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if dist(q, p) <= ptol {
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continue;
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}
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let before = quality(m.nodes, v);
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for step in [1.0, 0.5, 0.25] {
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let x = if step == 1.0 { q } else { place(g, targets, c, add(p, scale(sub(q, p), step)), ptol) };
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if let Some(slot) = m.nodes.get_mut(v as usize) {
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*slot = x;
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}
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if quality(m.nodes, v).keeps_above(before, floor) {
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moved = true;
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break;
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}
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if let Some(slot) = m.nodes.get_mut(v as usize) {
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*slot = p;
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}
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}
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}
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if !moved {
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break;
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}
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if let Some((_, _, nodes)) = finished {
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*m.nodes = nodes;
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}
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report
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}
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