66 lines
2.4 KiB
JavaScript
66 lines
2.4 KiB
JavaScript
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const SpacePick = (() => {
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"use strict";
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const {clamp, project} = typeof SpaceView === "object" ? SpaceView : require("./space-view.js");
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const {arcPoints} = typeof SpacePaint === "object" ? SpacePaint : require("./space-paint.js");
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const CURVE = 8;
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function gap(x, y, a, b) {
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const dx = b.x - a.x;
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const dy = b.y - a.y;
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const length = dx * dx + dy * dy;
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const share = length ? clamp(((x - a.x) * dx + (y - a.y) * dy) / length, 0, 1) : 0;
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return Math.hypot(a.x + dx * share - x, a.y + dy * share - y);
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}
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function nearest(x, y, marks) {
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if (marks.some((mark) => mark === null)) {
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return {distance: Infinity, depth: Infinity};
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}
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if (marks.length === 1) {
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return {distance: Math.hypot(marks[0].x - x, marks[0].y - y), depth: marks[0].depth};
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}
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let best = {distance: Infinity, depth: Infinity};
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for (let index = 1; index < marks.length; index += 1) {
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const distance = gap(x, y, marks[index - 1], marks[index]);
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if (distance < best.distance) {
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best = {distance, depth: (marks[index - 1].depth + marks[index].depth) / 2};
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}
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}
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return best;
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}
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function curve(marks) {
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if (marks.some((mark) => mark === null)) {
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return marks;
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}
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const [a, b, c] = marks;
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return Array.from({length: CURVE + 1}, (_, index) => {
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const t = index / CURVE;
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const u = 1 - t;
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return {x: u * u * a.x + 2 * u * t * b.x + t * t * c.x, y: u * u * a.y + 2 * u * t * b.y + t * t * c.y, depth: u * u * a.depth + 2 * u * t * b.depth + t * t * c.depth};
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});
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}
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function pick(built, cam, x, y, reach) {
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let best = null;
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const consider = (found, hit) => {
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if (found.distance > reach) {
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return;
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}
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if (!best || found.distance < best.distance - 0.5 || (found.distance <= best.distance + 0.5 && found.depth < best.depth)) {
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best = {...hit, distance: found.distance, depth: found.depth};
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}
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};
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built.lines.forEach((line, index) => consider(nearest(x, y, line.points.map((entry) => project(cam, entry))), {kind: "line", index, line}));
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built.arcs.forEach((arc, index) => {
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const marks = arcPoints(arc).map((entry) => project(cam, entry));
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consider(nearest(x, y, arc.kind === "broadcast" ? [...marks, marks[0]] : curve(marks)), {kind: "arc", index, arc});
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});
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return best;
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}
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return {pick};
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})();
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if (typeof module === "object" && module.exports) {
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module.exports = SpacePick;
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}
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