69 lines
1.6 KiB
JavaScript
69 lines
1.6 KiB
JavaScript
"use strict";
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Object.defineProperty(exports, "__esModule", {
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value: true
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});
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exports["default"] = void 0;
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/**
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* Knot insertion is known as "Boehm's algorithm"
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*
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* https://math.stackexchange.com/questions/417859/convert-a-b-spline-into-bezier-curves
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* code adapted from http://preserve.mactech.com/articles/develop/issue_25/schneider.html
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*/
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var _default = function _default(k, controlPoints, knots, newKnot) {
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var x = knots;
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var b = controlPoints;
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var n = controlPoints.length;
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var i = 0;
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var foundIndex = false;
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for (var j = 0; j < n + k; j++) {
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if (newKnot > x[j] && newKnot <= x[j + 1]) {
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i = j;
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foundIndex = true;
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break;
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}
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}
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if (!foundIndex) {
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throw new Error('invalid new knot');
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}
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var xHat = [];
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for (var _j = 0; _j < n + k + 1; _j++) {
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if (_j <= i) {
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xHat[_j] = x[_j];
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} else if (_j === i + 1) {
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xHat[_j] = newKnot;
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} else {
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xHat[_j] = x[_j - 1];
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}
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}
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var alpha;
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var bHat = [];
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for (var _j2 = 0; _j2 < n + 1; _j2++) {
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if (_j2 <= i - k + 1) {
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alpha = 1;
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} else if (i - k + 2 <= _j2 && _j2 <= i) {
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if (x[_j2 + k - 1] - x[_j2] === 0) {
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alpha = 0;
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} else {
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alpha = (newKnot - x[_j2]) / (x[_j2 + k - 1] - x[_j2]);
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}
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} else {
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alpha = 0;
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}
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if (alpha === 0) {
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bHat[_j2] = b[_j2 - 1];
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} else if (alpha === 1) {
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bHat[_j2] = b[_j2];
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} else {
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bHat[_j2] = {
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x: (1 - alpha) * b[_j2 - 1].x + alpha * b[_j2].x,
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y: (1 - alpha) * b[_j2 - 1].y + alpha * b[_j2].y
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};
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}
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}
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return {
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controlPoints: bHat,
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knots: xHat
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};
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};
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exports["default"] = _default; |