selune
9f88537927
A SolidCraft-owned portable B-rep schema (geometry schema 2 with analytic curves and surfaces, explicit frames and ranges, fitted intersection curves) and a versioned body envelope (SCBREP03) with its own metadata records, a bounded binary codec, a validator with resource budgets, and an adapter that refuses what it can't convert exactly. Pinned by a box-and-fillet golden fixture. Not yet written by application saves. Refs #303.
86 lines
3.9 KiB
Rust
86 lines
3.9 KiB
Rust
//! Bounded export of procedural intersections as ordinary spatial cubic splines.
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//! The stored tolerance is the fitting target; the result is always provisional.
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use super::*;
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fn point_at(c: &mt::Curve, t: f64, budget: &mut usize) -> Result<mt::Point3> {
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*budget = budget.checked_sub(1).ok_or_else(|| invalid("intersection fitting budget"))?;
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let p = c.subs(t);
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if !p.x.is_finite() || !p.y.is_finite() || !p.z.is_finite() {
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return Err(invalid("intersection sample"));
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}
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Ok(p)
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}
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pub(super) fn fit_intersection(c: &mt::Curve, budget: &mut usize) -> Result<b::Curve> {
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let tolerance = 1e-4;
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let (start, end) = c.range_tuple();
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if !start.is_finite() || !end.is_finite() || start >= end {
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return Err(invalid("intersection range"));
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}
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// Fit each smooth parameter interval using spatial samples, without backend derivative conventions.
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// Only the resulting spatial spline crosses the persisted format boundary.
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let mt::Curve::IntersectionCurve(intersection) = c else {
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return Err(invalid("expected intersection"));
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};
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let mut breaks = vec![start, end];
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match intersection.leader() {
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mt::Leader::Polyline(points) => {
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if points.len() > 4096 {
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return Err(invalid("intersection parameter budget"));
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}
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breaks.extend((0..points.len()).map(|i| i as f64).filter(|t| *t > start && *t < end));
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}
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mt::Leader::BSpline(curve) => {
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if curve.knot_vec().len() > 4096 {
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return Err(invalid("intersection parameter budget"));
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}
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breaks.extend(curve.knot_vec().iter().copied().filter(|t| *t > start && *t < end));
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}
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}
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breaks.sort_by(f64::total_cmp);
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breaks.dedup();
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let mut stack = Vec::new();
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for pair in breaks.windows(2).rev() {
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let (a, b) = (pair[0], pair[1]);
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stack.push((a, b, point_at(c, a, budget)?, point_at(c, b, budget)?, 0u8));
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}
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let mut pieces = Vec::new();
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while let Some((a, b, pa, pb, depth)) = stack.pop() {
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let p1 = point_at(c, a + (b - a) / 3., budget)?.to_vec();
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let p2 = point_at(c, a + (b - a) * 2. / 3., budget)?.to_vec();
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let x = p1 * 27. - pa.to_vec() * 8. - pb.to_vec();
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let y = p2 * 27. - pa.to_vec() - pb.to_vec() * 8.;
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let controls = [pa, mt::Point3::from_vec((x * 2. - y) / 18.), mt::Point3::from_vec((y * 2. - x) / 18.), pb];
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let mut fits = true;
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for fraction in [0.125, 0.25, 0.5, 0.75, 0.875] {
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let actual = point_at(c, a + (b - a) * fraction, budget)?;
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let u = 1. - fraction;
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let fitted = controls[0].to_vec() * u * u * u
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+ controls[1].to_vec() * 3. * u * u * fraction
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+ controls[2].to_vec() * 3. * u * fraction * fraction
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+ controls[3].to_vec() * fraction * fraction * fraction;
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if (actual.to_vec() - fitted).magnitude() > tolerance * 0.1 {
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fits = false;
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}
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}
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if fits {
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pieces.push((a, b, controls));
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} else {
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if depth >= 12 || pieces.len() + stack.len() >= 1023 {
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return Err(invalid("intersection fit did not converge"));
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}
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let middle = a + (b - a) / 2.;
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let pm = point_at(c, middle, budget)?;
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stack.push((middle, b, pm, pb, depth + 1));
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stack.push((a, middle, pa, pm, depth + 1));
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}
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}
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let first = pieces.first().ok_or_else(|| invalid("empty intersection fit"))?;
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let mut points = vec![point(first.2[0])];
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let mut knots = vec![start; 4];
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for (i, (_, b, controls)) in pieces.iter().enumerate() {
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points.extend(controls.iter().skip(1).copied().map(point));
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knots.extend(std::iter::repeat_n(*b, if i + 1 == pieces.len() { 4 } else { 3 }));
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}
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Ok(b::Curve::Intersection { knots, points, fitting_tolerance: tolerance, faces: None })
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}
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