feat(core): polyline coping axis with per-stretch frames (bent coping stage 1)

- buildAxis: IP1 → IP4 → IP3 as stretches with their own frames; arc length s
  from IP1; mitre normal u1 + u2 at the kink.
- toAxis / fromAxis: world ↔ (k, s, n) round trip; stretch chosen by the mitre plane.
- copingSpan (centred on L_IP/2) and nearKink (columns within the Level half-width).
- Straight P1 regression against spec §12 bearing values; bent round trip and continuity.
- Not wired into buildPier yet; the model still refuses bent coping (미실시).

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>
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ypshimandClaude Haiku 5.5 committed 2026-10-22 09:18:31 +09:00
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import type { Vec2 } from './geometry';
/**
* Coping axis as a polyline IP1 → (IP4) → IP3 (spec §4.1). Each stretch is straight and has its own frame.
* Coordinates: k = stretch index, s = arc length from IP1 (the same s for both stretches), n = offset to the right of u.
* The lateral offset uses the same convention as the straight model: nrm = (u.n, −u.e).
*/
export interface AxisSegment {
start: Vec2;
u: Vec2;
nrm: Vec2;
/** Arc length at the start of this stretch. */
s0: number;
}
export interface Axis {
segments: AxisSegment[];
/** Total arc length L_IP. */
length: number;
/** Bend point IP4, or null for a straight axis. */
kink: Vec2 | null;
/** Mitre normal u1 + u2 (unit) at the kink; null for a straight axis. A point is on stretch 0 when (p − kink)·mitre ≤ 0. */
mitre: Vec2 | null;
}
export interface AxisPoint {
k: number;
s: number;
n: number;
}
const dist = (a: Vec2, b: Vec2) => Math.hypot(b.e - a.e, b.n - a.n);
const sub = (a: Vec2, b: Vec2): Vec2 => ({ e: a.e - b.e, n: a.n - b.n });
const dot = (a: Vec2, b: Vec2) => a.e * b.e + a.n * b.n;
const unit = (v: Vec2): Vec2 => {
const len = Math.hypot(v.e, v.n);
if (len === 0) throw new Error('축 길이가 0입니다.');
return { e: v.e / len, n: v.n / len };
};
function frame(start: Vec2, end: Vec2): { u: Vec2; nrm: Vec2 } {
const u = unit(sub(end, start));
return { u, nrm: { e: u.n, n: -u.e } };
}
export function buildAxis(ip1: Vec2, ip3: Vec2, kink: Vec2 | null): Axis {
if (!kink) {
const f = frame(ip1, ip3);
return { segments: [{ start: ip1, ...f, s0: 0 }], length: dist(ip1, ip3), kink: null, mitre: null };
}
const a = dist(ip1, kink);
const f1 = frame(ip1, kink);
const f2 = frame(kink, ip3);
return {
segments: [
{ start: ip1, ...f1, s0: 0 },
{ start: kink, ...f2, s0: a },
],
length: a + dist(kink, ip3),
kink,
mitre: unit({ e: f1.u.e + f2.u.e, n: f1.u.n + f2.u.n }),
};
}
/** Stretch and local coordinates of a world point. Points on the stretch-0 side of the mitre plane belong to stretch 0. */
export function toAxis(axis: Axis, p: Vec2): AxisPoint {
const k = axis.mitre && axis.kink && dot(sub(p, axis.kink), axis.mitre) > 0 ? 1 : 0;
const seg = axis.segments[k];
const d = sub(p, seg.start);
return { k, s: seg.s0 + dot(d, seg.u), n: dot(d, seg.nrm) };
}
/** World point of local coordinates (inverse of toAxis for the same k). */
export function fromAxis(axis: Axis, q: AxisPoint): Vec2 {
const seg = axis.segments[q.k];
const ds = q.s - seg.s0;
return {
e: seg.start.e + ds * seg.u.e + q.n * seg.nrm.e,
n: seg.start.n + ds * seg.u.n + q.n * seg.nrm.n,
};
}
/** Arc-length span of the coping of length L, centred on the axis (spec §4.2: centre at L_IP / 2). */
export function copingSpan(axis: Axis, L: number): { sStart: number; sEnd: number } {
return { sStart: axis.length / 2 - L / 2, sEnd: axis.length / 2 + L / 2 };
}
/** Arc length of the kink, or null for a straight axis. */
export function kinkArc(axis: Axis): number | null {
return axis.kink ? axis.segments[1].s0 : null;
}
/** Positions (arc length) closer than minDistance to the kink. Used to refuse columns at the bend. */
export function nearKink(axis: Axis, sPositions: number[], minDistance: number): number[] {
const a = kinkArc(axis);
if (a === null) return [];
return sPositions.filter((s) => Math.abs(s - a) < minDistance);
}
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import { describe, expect, it } from 'vitest';
import { DIM, solveIp4 } from '../src/core/geometry';
import { buildAxis, copingSpan, fromAxis, kinkArc, nearKink, toAxis } from '../src/core/axis';
import type { PierInput } from '../src/core/types';
import { loadP1 } from './helpers';
const pt = (p: PierInput['ips'][number]) => ({ e: p.x, n: p.y });
const ip = (p: PierInput, name: string) => pt(p.ips.find((q) => q.name === name)!);
describe('straight axis (regression against spec §12)', () => {
const p1 = loadP1();
const axis = buildAxis(ip(p1, 'IP1'), ip(p1, 'IP3'), null);
const bp1 = copingSpan(axis, p1.copingLengthMm / 1000).sStart;
it('bearing s and n relative to BP1 match spec §12', () => {
const front = p1.bearings.filter((b) => b.row === '전열').sort((a, b) => a.no - b.no);
const back = p1.bearings.filter((b) => b.row === '후열').sort((a, b) => a.no - b.no);
const fs = front.map((b) => toAxis(axis, { e: b.x, n: b.y }));
const bs = back.map((b) => toAxis(axis, { e: b.x, n: b.y }));
expect(fs[0].s - bp1).toBeCloseTo(0.943, 3);
expect(fs[fs.length - 1].s - bp1).toBeCloseTo(10.965, 3);
expect(bs[0].s - bp1).toBeCloseTo(1.029, 3);
expect(bs[bs.length - 1].s - bp1).toBeCloseTo(11.05, 3);
expect(fs[0].n).toBeCloseTo(-0.698, 3);
expect(bs[0].n).toBeCloseTo(0.6, 3);
});
it('straight axis: every point is on stretch 0 and round-trips', () => {
for (const b of p1.bearings) {
const p = { e: b.x, n: b.y };
const q = toAxis(axis, p);
expect(q.k).toBe(0);
const back = fromAxis(axis, q);
expect(back.e).toBeCloseTo(p.e, 9);
expect(back.n).toBeCloseTo(p.n, 9);
}
});
});
// Synthetic bend: IP1 (0, 0), IP2 (1, 0), IP3 (6, 2), 60° right turn. The P1 sheet is straight (IP1, IP2, IP3 collinear),
// so P1 cannot exercise a bend. The kink falls at about s = 7.15 m, inside a 6 m coping centred on the axis.
describe('bent axis IP1 → IP4 → IP3', () => {
const p1 = loadP1();
const ip1 = { e: 0, n: 0 };
const ip2 = { e: 1, n: 0 };
const ip3 = { e: 6, n: 2 };
const kink = solveIp4(ip1, ip2, ip3, 60)!;
const axis = buildAxis(ip1, ip3, kink);
const a = kinkArc(axis)!;
it('kink lies on the IP1→IP2 line, at s ≈ 7.15, and the arc length adds the two stretches', () => {
const cross = (kink.e - ip1.e) * (ip2.n - ip1.n) - (kink.n - ip1.n) * (ip2.e - ip1.e);
expect(cross).toBeCloseTo(0, 9);
expect(a).toBeCloseTo(7.15, 1);
const len2 = Math.hypot(ip3.e - kink.e, ip3.n - kink.n);
expect(axis.length).toBeCloseTo(a + len2, 9);
});
it('the kink is the continuity point: s = a on both stretches at n = 0', () => {
const from0 = fromAxis(axis, { k: 0, s: a, n: 0 });
const from1 = fromAxis(axis, { k: 1, s: a, n: 0 });
expect(from0.e).toBeCloseTo(kink.e, 9);
expect(from0.n).toBeCloseTo(kink.n, 9);
expect(from1.e).toBeCloseTo(kink.e, 9);
expect(from1.n).toBeCloseTo(kink.n, 9);
});
it('every bearing keeps its input world coordinates through toAxis → fromAxis', () => {
for (const b of p1.bearings) {
const p = { e: b.x, n: b.y };
const back = fromAxis(axis, toAxis(axis, p));
expect(back.e).toBeCloseTo(p.e, 9);
expect(back.n).toBeCloseTo(p.n, 9);
}
});
it('a point just before the mitre plane is on stretch 0, just after it on stretch 1', () => {
const u1 = axis.segments[0].u;
const u2 = axis.segments[1].u;
const before = { e: kink.e - 0.01 * u1.e, n: kink.n - 0.01 * u1.n };
const after = { e: kink.e + 0.01 * u2.e, n: kink.n + 0.01 * u2.n };
expect(toAxis(axis, before).k).toBe(0);
expect(toAxis(axis, after).k).toBe(1);
});
it('coping centred on the axis: span is L_IP/2 ± L/2 and the kink lies inside it', () => {
const L = 6;
const span = copingSpan(axis, L);
expect(span.sStart).toBeCloseTo(axis.length / 2 - L / 2, 9);
expect(span.sStart < a && a < span.sEnd).toBe(true);
});
it('columns within the Level half-width of the kink are reported', () => {
const half = DIM.levelWidth / 2;
const columns = [a - 0.5, a + 5];
expect(nearKink(axis, columns, half)).toEqual([a - 0.5]);
expect(nearKink(axis, [a + 5], half)).toEqual([]);
});
});