Fixing mid point calculation precision
This commit is contained in:
Mark Tolmacs
parent
3363e0e289
commit
02b4fa1ca7
@ -10,7 +10,7 @@ import {
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isCurve,
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isLineSegment,
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curveLength,
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curveHalfPoint,
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curvePointAtLength,
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} from "@excalidraw/math";
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import { getCurvePathOps } from "@excalidraw/utils/shape";
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@ -707,7 +707,7 @@ export class LinearElementEditor {
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switch (true) {
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case isCurve(shape):
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return curveHalfPoint(shape as Curve<GlobalPoint>);
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return curvePointAtLength(shape as Curve<GlobalPoint>, 0.5);
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case isLineSegment(shape):
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return pointCenter(shape[0] as GlobalPoint, shape[1] as GlobalPoint);
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}
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@ -346,12 +346,12 @@ describe("Test Linear Elements", () => {
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expect(midPointsWithRoundEdge).toMatchInlineSnapshot(`
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[
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[
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"56.87500",
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"48.12500",
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"54.27552",
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"46.16120",
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],
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[
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"79.37500",
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"48.12500",
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"76.95494",
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"44.56052",
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],
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]
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`);
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@ -411,12 +411,12 @@ describe("Test Linear Elements", () => {
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expect(newMidPoints).toMatchInlineSnapshot(`
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[
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[
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"106.87500",
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"68.12500",
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"104.27552",
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"66.16120",
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],
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[
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"129.37500",
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"68.12500",
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"126.95494",
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"64.56052",
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],
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]
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`);
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@ -727,12 +727,12 @@ describe("Test Linear Elements", () => {
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expect(newMidPoints).toMatchInlineSnapshot(`
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[
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[
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"31.87500",
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"23.12500",
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"29.28349",
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"20.91105",
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],
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[
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"82.50000",
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"51.25000",
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"78.86048",
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"46.12277",
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],
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]
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`);
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@ -816,12 +816,12 @@ describe("Test Linear Elements", () => {
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expect(newMidPoints).toMatchInlineSnapshot(`
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[
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[
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"56.87500",
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"48.12500",
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"54.27552",
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"46.16120",
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],
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[
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"79.37500",
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"48.12500",
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"76.95494",
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"44.56052",
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],
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]
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`);
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@ -983,8 +983,8 @@ describe("Test Linear Elements", () => {
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);
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expect(position).toMatchInlineSnapshot(`
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{
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"x": "90.23300",
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"y": "81.68631",
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"x": "86.17305",
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"y": "76.11251",
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}
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`);
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});
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@ -383,25 +383,22 @@ const proxy = <T extends ExcalidrawElement>(
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the proxy */
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get(): typeof element;
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} => {
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return new Proxy(
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{},
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{
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get(target, prop) {
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const currentElement = h.elements.find(
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({ id }) => id === element.id,
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) as any;
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if (prop === "get") {
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if (currentElement.hasOwnProperty("get")) {
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throw new Error(
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"trying to get `get` test property, but ExcalidrawElement seems to define its own",
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);
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}
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return () => currentElement;
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return new Proxy(element, {
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get(target, prop) {
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const currentElement = h.elements.find(
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({ id }) => id === element.id,
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) as any;
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if (prop === "get") {
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if (currentElement.hasOwnProperty("get")) {
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throw new Error(
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"trying to get `get` test property, but ExcalidrawElement seems to define its own",
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);
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}
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return currentElement[prop];
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},
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return () => currentElement;
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}
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return currentElement[prop];
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},
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) as any;
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}) as any;
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};
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/** Tools that can be used to draw shapes */
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55
packages/math/src/constants.ts
Normal file
55
packages/math/src/constants.ts
Normal file
@ -0,0 +1,55 @@
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// Legendre-Gauss abscissae (x values) and weights for n=24
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// Refeerence: https://pomax.github.io/bezierinfo/legendre-gauss.html
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export const LegendreGaussN24TValues = [
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-0.0640568928626056260850430826247450385909,
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0.0640568928626056260850430826247450385909,
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-0.1911188674736163091586398207570696318404,
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0.1911188674736163091586398207570696318404,
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-0.3150426796961633743867932913198102407864,
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0.3150426796961633743867932913198102407864,
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-0.4337935076260451384870842319133497124524,
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0.4337935076260451384870842319133497124524,
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-0.5454214713888395356583756172183723700107,
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0.5454214713888395356583756172183723700107,
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-0.6480936519369755692524957869107476266696,
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0.6480936519369755692524957869107476266696,
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-0.7401241915785543642438281030999784255232,
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0.7401241915785543642438281030999784255232,
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-0.8200019859739029219539498726697452080761,
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0.8200019859739029219539498726697452080761,
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-0.8864155270044010342131543419821967550873,
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0.8864155270044010342131543419821967550873,
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-0.9382745520027327585236490017087214496548,
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0.9382745520027327585236490017087214496548,
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-0.9747285559713094981983919930081690617411,
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0.9747285559713094981983919930081690617411,
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-0.9951872199970213601799974097007368118745,
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0.9951872199970213601799974097007368118745,
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];
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export const LegendreGaussN24CValues = [
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0.1279381953467521569740561652246953718517,
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0.1279381953467521569740561652246953718517,
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0.1258374563468282961213753825111836887264,
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0.1258374563468282961213753825111836887264,
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0.121670472927803391204463153476262425607,
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0.121670472927803391204463153476262425607,
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0.1155056680537256013533444839067835598622,
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0.1155056680537256013533444839067835598622,
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0.1074442701159656347825773424466062227946,
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0.1074442701159656347825773424466062227946,
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0.0976186521041138882698806644642471544279,
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0.0976186521041138882698806644642471544279,
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0.086190161531953275917185202983742667185,
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0.086190161531953275917185202983742667185,
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0.0733464814110803057340336152531165181193,
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0.0733464814110803057340336152531165181193,
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0.0592985849154367807463677585001085845412,
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0.0592985849154367807463677585001085845412,
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0.0442774388174198061686027482113382288593,
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0.0442774388174198061686027482113382288593,
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0.0285313886289336631813078159518782864491,
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0.0285313886289336631813078159518782864491,
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0.0123412297999871995468056670700372915759,
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0.0123412297999871995468056670700372915759,
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];
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@ -1,16 +1,7 @@
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import { invariant } from "@excalidraw/common";
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import type { Bounds } from "@excalidraw/element";
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import {
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isPoint,
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pointCenter,
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pointDistance,
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pointFrom,
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pointFromVector,
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} from "./point";
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import { isPoint, pointDistance, pointFrom, pointFromVector } from "./point";
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import { rectangle, rectangleIntersectLineSegment } from "./rectangle";
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import { vector, vectorNormal, vectorNormalize, vectorScale } from "./vector";
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import { LegendreGaussN24CValues, LegendreGaussN24TValues } from "./constants";
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import type { Curve, GlobalPoint, LineSegment, LocalPoint } from "./types";
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@ -31,81 +22,6 @@ export function curve<Point extends GlobalPoint | LocalPoint>(
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return [a, b, c, d] as Curve<Point>;
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}
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function gradient(
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f: (t: number, s: number) => number,
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t0: number,
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s0: number,
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delta: number = 1e-6,
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): number[] {
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return [
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(f(t0 + delta, s0) - f(t0 - delta, s0)) / (2 * delta),
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(f(t0, s0 + delta) - f(t0, s0 - delta)) / (2 * delta),
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];
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}
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function solve(
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f: (t: number, s: number) => [number, number],
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t0: number,
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s0: number,
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tolerance: number = 1e-3,
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iterLimit: number = 10,
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): number[] | null {
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let error = Infinity;
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let iter = 0;
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while (error >= tolerance) {
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if (iter >= iterLimit) {
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return null;
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}
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const y0 = f(t0, s0);
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const jacobian = [
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gradient((t, s) => f(t, s)[0], t0, s0),
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gradient((t, s) => f(t, s)[1], t0, s0),
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];
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const b = [[-y0[0]], [-y0[1]]];
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const det =
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jacobian[0][0] * jacobian[1][1] - jacobian[0][1] * jacobian[1][0];
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if (det === 0) {
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return null;
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}
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const iJ = [
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[jacobian[1][1] / det, -jacobian[0][1] / det],
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[-jacobian[1][0] / det, jacobian[0][0] / det],
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];
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const h = [
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[iJ[0][0] * b[0][0] + iJ[0][1] * b[1][0]],
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[iJ[1][0] * b[0][0] + iJ[1][1] * b[1][0]],
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];
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t0 = t0 + h[0][0];
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s0 = s0 + h[1][0];
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const [tErr, sErr] = f(t0, s0);
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error = Math.max(Math.abs(tErr), Math.abs(sErr));
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iter += 1;
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}
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return [t0, s0];
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}
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export const bezierEquation = <Point extends GlobalPoint | LocalPoint>(
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c: Curve<Point>,
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t: number,
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) =>
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pointFrom<Point>(
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(1 - t) ** 3 * c[0][0] +
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3 * (1 - t) ** 2 * t * c[1][0] +
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3 * (1 - t) * t ** 2 * c[2][0] +
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t ** 3 * c[3][0],
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(1 - t) ** 3 * c[0][1] +
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3 * (1 - t) ** 2 * t * c[1][1] +
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3 * (1 - t) * t ** 2 * c[2][1] +
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t ** 3 * c[3][1],
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);
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/**
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* Computes the intersection between a cubic spline and a line segment.
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*/
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@ -113,12 +29,19 @@ export function curveIntersectLineSegment<
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Point extends GlobalPoint | LocalPoint,
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>(c: Curve<Point>, l: LineSegment<Point>): Point[] {
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// Optimize by doing a cheap bounding box check first
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const bounds = curveBounds(c);
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const [p0, p1, p2, p3] = c;
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if (
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rectangleIntersectLineSegment(
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rectangle(
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pointFrom(bounds[0], bounds[1]),
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pointFrom(bounds[2], bounds[3]),
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pointFrom(
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Math.min(p0[0], p1[0], p2[0], p3[0]),
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Math.min(p0[1], p1[1], p2[1], p3[1]),
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),
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pointFrom(
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Math.max(p0[0], p1[0], p2[0], p3[0]),
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Math.max(p0[1], p1[1], p2[1], p3[1]),
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),
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),
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l,
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).length === 0
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@ -303,15 +226,6 @@ export function curveTangent<Point extends GlobalPoint | LocalPoint>(
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);
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}
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function curveBounds<Point extends GlobalPoint | LocalPoint>(
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c: Curve<Point>,
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): Bounds {
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const [P0, P1, P2, P3] = c;
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const x = [P0[0], P1[0], P2[0], P3[0]];
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const y = [P0[1], P1[1], P2[1], P3[1]];
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return [Math.min(...x), Math.min(...y), Math.max(...x), Math.max(...y)];
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}
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export function curveCatmullRomQuadraticApproxPoints(
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points: GlobalPoint[],
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tension = 0.5,
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@ -417,42 +331,201 @@ export function offsetPointsForQuadraticBezier(
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return offsetPoints;
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}
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/**
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* Implementation based on Legendre-Gauss quadrature for more accurate arc
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* length calculation.
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*
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* Reference: https://pomax.github.io/bezierinfo/#arclength
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*
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* @param c The curve to calculate the length of
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* @returns The approximated length of the curve
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*/
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export function curveLength<P extends GlobalPoint | LocalPoint>(
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c: Curve<P>,
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): number {
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// Use numerical integration to approximate the curve length
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const steps = 50;
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let length = 0;
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const z2 = 0.5;
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let sum = 0;
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// Calculate length by summing segments
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let prevPoint = bezierEquation(c, 0);
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for (let i = 1; i <= steps; i++) {
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const t = i / steps;
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const currentPoint = bezierEquation(c, t);
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length += pointDistance(prevPoint, currentPoint);
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prevPoint = currentPoint;
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for (let i = 0; i < 24; i++) {
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const t = z2 * LegendreGaussN24TValues[i] + z2;
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const derivativeVector = curveTangent(c, t);
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const magnitude = Math.sqrt(
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derivativeVector[0] * derivativeVector[0] +
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derivativeVector[1] * derivativeVector[1],
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);
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sum += LegendreGaussN24CValues[i] * magnitude;
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}
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return length;
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return z2 * sum;
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}
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export function curveHalfPoint<P extends GlobalPoint | LocalPoint>(
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/**
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* Calculates the curve length from t=0 to t=parameter using the same
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* Legendre-Gauss quadrature method used in curveLength
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*
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* @param c The curve to calculate the partial length for
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* @param t The parameter value (0 to 1) to calculate length up to
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* @returns The length of the curve from beginning to parameter t
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*/
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export function curveLengthAtParameter<P extends GlobalPoint | LocalPoint>(
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c: Curve<P>,
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): P {
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const steps = 50;
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const halfLength = curveLength(c) / 2;
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let length = 0;
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let prevPoint = bezierEquation(c, 0);
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for (let i = 1; i <= steps; i++) {
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const t = i / steps;
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const currentPoint = bezierEquation(c, t);
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length += pointDistance(prevPoint, currentPoint);
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if (length > halfLength) {
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return pointCenter(prevPoint, currentPoint);
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}
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prevPoint = currentPoint;
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t: number,
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): number {
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if (t <= 0) {
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return 0;
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}
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if (t >= 1) {
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return curveLength(c);
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}
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invariant(false, "No half point found (this should not happen)");
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// Scale and shift the integration interval from [0,t] to [-1,1]
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// which is what the Legendre-Gauss quadrature expects
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const z1 = t / 2;
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const z2 = t / 2;
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let sum = 0;
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for (let i = 0; i < 24; i++) {
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const parameter = z1 * LegendreGaussN24TValues[i] + z2;
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const derivativeVector = curveTangent(c, parameter);
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const magnitude = Math.sqrt(
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derivativeVector[0] * derivativeVector[0] +
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derivativeVector[1] * derivativeVector[1],
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);
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sum += LegendreGaussN24CValues[i] * magnitude;
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}
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return z1 * sum; // Scale the result back to the original interval
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}
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/**
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* Calculates the point at a specific percentage of a curve's total length
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* using binary search for improved efficiency and accuracy.
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*
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* @param c The curve to calculate point on
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* @param percent A value between 0 and 1 representing the percentage of the curve's length
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* @returns The point at the specified percentage of curve length
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*/
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export function curvePointAtLength<P extends GlobalPoint | LocalPoint>(
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c: Curve<P>,
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percent: number,
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): P {
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if (percent <= 0) {
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return bezierEquation(c, 0);
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}
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if (percent >= 1) {
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return bezierEquation(c, 1);
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}
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const totalLength = curveLength(c);
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const targetLength = totalLength * percent;
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||||
// Binary search to find parameter t where length at t equals target length
|
||||
let tMin = 0;
|
||||
let tMax = 1;
|
||||
let t = percent; // Start with a reasonable guess (t = percent)
|
||||
let currentLength = 0;
|
||||
|
||||
// Tolerance for length comparison and iteration limit to avoid infinite loops
|
||||
const tolerance = totalLength * 0.0001; // 0.01% of total length
|
||||
const maxIterations = 20;
|
||||
|
||||
for (let iteration = 0; iteration < maxIterations; iteration++) {
|
||||
currentLength = curveLengthAtParameter(c, t);
|
||||
const error = Math.abs(currentLength - targetLength);
|
||||
|
||||
// If we're close enough, return the point
|
||||
if (error < tolerance) {
|
||||
break;
|
||||
}
|
||||
|
||||
// Update search range
|
||||
if (currentLength < targetLength) {
|
||||
tMin = t;
|
||||
} else {
|
||||
tMax = t;
|
||||
}
|
||||
|
||||
// Update parameter using bisection method
|
||||
t = (tMin + tMax) / 2;
|
||||
}
|
||||
|
||||
return bezierEquation(c, t);
|
||||
}
|
||||
|
||||
function bezierEquation<Point extends GlobalPoint | LocalPoint>(
|
||||
c: Curve<Point>,
|
||||
t: number,
|
||||
) {
|
||||
return pointFrom<Point>(
|
||||
(1 - t) ** 3 * c[0][0] +
|
||||
3 * (1 - t) ** 2 * t * c[1][0] +
|
||||
3 * (1 - t) * t ** 2 * c[2][0] +
|
||||
t ** 3 * c[3][0],
|
||||
(1 - t) ** 3 * c[0][1] +
|
||||
3 * (1 - t) ** 2 * t * c[1][1] +
|
||||
3 * (1 - t) * t ** 2 * c[2][1] +
|
||||
t ** 3 * c[3][1],
|
||||
);
|
||||
}
|
||||
|
||||
function gradient(
|
||||
f: (t: number, s: number) => number,
|
||||
t0: number,
|
||||
s0: number,
|
||||
delta: number = 1e-6,
|
||||
): number[] {
|
||||
return [
|
||||
(f(t0 + delta, s0) - f(t0 - delta, s0)) / (2 * delta),
|
||||
(f(t0, s0 + delta) - f(t0, s0 - delta)) / (2 * delta),
|
||||
];
|
||||
}
|
||||
|
||||
function solve(
|
||||
f: (t: number, s: number) => [number, number],
|
||||
t0: number,
|
||||
s0: number,
|
||||
tolerance: number = 1e-3,
|
||||
iterLimit: number = 10,
|
||||
): number[] | null {
|
||||
let error = Infinity;
|
||||
let iter = 0;
|
||||
|
||||
while (error >= tolerance) {
|
||||
if (iter >= iterLimit) {
|
||||
return null;
|
||||
}
|
||||
|
||||
const y0 = f(t0, s0);
|
||||
const jacobian = [
|
||||
gradient((t, s) => f(t, s)[0], t0, s0),
|
||||
gradient((t, s) => f(t, s)[1], t0, s0),
|
||||
];
|
||||
const b = [[-y0[0]], [-y0[1]]];
|
||||
const det =
|
||||
jacobian[0][0] * jacobian[1][1] - jacobian[0][1] * jacobian[1][0];
|
||||
|
||||
if (det === 0) {
|
||||
return null;
|
||||
}
|
||||
|
||||
const iJ = [
|
||||
[jacobian[1][1] / det, -jacobian[0][1] / det],
|
||||
[-jacobian[1][0] / det, jacobian[0][0] / det],
|
||||
];
|
||||
const h = [
|
||||
[iJ[0][0] * b[0][0] + iJ[0][1] * b[1][0]],
|
||||
[iJ[1][0] * b[0][0] + iJ[1][1] * b[1][0]],
|
||||
];
|
||||
|
||||
t0 = t0 + h[0][0];
|
||||
s0 = s0 + h[1][0];
|
||||
|
||||
const [tErr, sErr] = f(t0, s0);
|
||||
error = Math.max(Math.abs(tErr), Math.abs(sErr));
|
||||
iter += 1;
|
||||
}
|
||||
|
||||
return [t0, s0];
|
||||
}
|
||||
|
||||
@ -1,4 +1,5 @@
|
||||
export * from "./angle";
|
||||
export * from "./constants";
|
||||
export * from "./curve";
|
||||
export * from "./line";
|
||||
export * from "./point";
|
||||
|
||||
@ -4,6 +4,9 @@ import {
|
||||
curve,
|
||||
curveClosestPoint,
|
||||
curveIntersectLineSegment,
|
||||
curveLength,
|
||||
curveLengthAtParameter,
|
||||
curvePointAtLength,
|
||||
curvePointDistance,
|
||||
} from "../src/curve";
|
||||
import { pointFrom } from "../src/point";
|
||||
@ -99,4 +102,45 @@ describe("Math curve", () => {
|
||||
expect(curvePointDistance(c, p)).toBeCloseTo(6.695873043213627);
|
||||
});
|
||||
});
|
||||
|
||||
describe("length", () => {
|
||||
it("can be determined", () => {
|
||||
const c = curve(
|
||||
pointFrom(-50, -50),
|
||||
pointFrom(10, -50),
|
||||
pointFrom(10, 50),
|
||||
pointFrom(50, 50),
|
||||
);
|
||||
|
||||
expect(curveLength(c)).toBeCloseTo(150.0, 0);
|
||||
});
|
||||
});
|
||||
|
||||
describe("point at given parameter", () => {
|
||||
it("can be determined", () => {
|
||||
const c = curve(
|
||||
pointFrom(-50, -50),
|
||||
pointFrom(10, -50),
|
||||
pointFrom(10, 50),
|
||||
pointFrom(50, 50),
|
||||
);
|
||||
|
||||
expect(curveLengthAtParameter(c, 0.5)).toBeCloseTo(80.83);
|
||||
});
|
||||
});
|
||||
|
||||
describe("point at given length", () => {
|
||||
it("can be determined", () => {
|
||||
const c = curve(
|
||||
pointFrom(-50, -50),
|
||||
pointFrom(10, -50),
|
||||
pointFrom(10, 50),
|
||||
pointFrom(50, 50),
|
||||
);
|
||||
|
||||
expect(curvePointAtLength(c, 0.5)).toEqual([
|
||||
4.802938740176614, -5.301185927237384,
|
||||
]);
|
||||
});
|
||||
});
|
||||
});
|
||||
|
||||
Loading…
x
Reference in New Issue
Block a user