102 lines
3.2 KiB
JavaScript
102 lines
3.2 KiB
JavaScript
import {cartesian} from "../cartesian.js";
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import {abs, asin, atan2, cos, epsilon, radians, sqrt} from "../math.js";
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import {transformer} from "../transform.js";
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var maxDepth = 16, // maximum depth of subdivision
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cosMinDistance = cos(30 * radians); // cos(minimum angular distance)
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export default function(project, delta2) {
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return +delta2 ? resample(project, delta2) : resampleNone(project);
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}
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function resampleNone(project) {
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return transformer({
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point: function(x, y) {
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x = project(x, y);
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this.stream.point(x[0], x[1]);
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}
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});
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}
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function resample(project, delta2) {
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function resampleLineTo(x0, y0, lambda0, a0, b0, c0, x1, y1, lambda1, a1, b1, c1, depth, stream) {
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var dx = x1 - x0,
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dy = y1 - y0,
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d2 = dx * dx + dy * dy;
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if (d2 > 4 * delta2 && depth--) {
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var a = a0 + a1,
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b = b0 + b1,
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c = c0 + c1,
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m = sqrt(a * a + b * b + c * c),
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phi2 = asin(c /= m),
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lambda2 = abs(abs(c) - 1) < epsilon || abs(lambda0 - lambda1) < epsilon ? (lambda0 + lambda1) / 2 : atan2(b, a),
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p = project(lambda2, phi2),
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x2 = p[0],
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y2 = p[1],
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dx2 = x2 - x0,
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dy2 = y2 - y0,
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dz = dy * dx2 - dx * dy2;
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if (dz * dz / d2 > delta2 // perpendicular projected distance
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|| abs((dx * dx2 + dy * dy2) / d2 - 0.5) > 0.3 // midpoint close to an end
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|| a0 * a1 + b0 * b1 + c0 * c1 < cosMinDistance) { // angular distance
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resampleLineTo(x0, y0, lambda0, a0, b0, c0, x2, y2, lambda2, a /= m, b /= m, c, depth, stream);
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stream.point(x2, y2);
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resampleLineTo(x2, y2, lambda2, a, b, c, x1, y1, lambda1, a1, b1, c1, depth, stream);
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}
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}
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}
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return function(stream) {
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var lambda00, x00, y00, a00, b00, c00, // first point
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lambda0, x0, y0, a0, b0, c0; // previous point
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var resampleStream = {
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point: point,
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lineStart: lineStart,
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lineEnd: lineEnd,
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polygonStart: function() { stream.polygonStart(); resampleStream.lineStart = ringStart; },
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polygonEnd: function() { stream.polygonEnd(); resampleStream.lineStart = lineStart; }
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};
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function point(x, y) {
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x = project(x, y);
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stream.point(x[0], x[1]);
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}
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function lineStart() {
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x0 = NaN;
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resampleStream.point = linePoint;
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stream.lineStart();
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}
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function linePoint(lambda, phi) {
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var c = cartesian([lambda, phi]), p = project(lambda, phi);
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resampleLineTo(x0, y0, lambda0, a0, b0, c0, x0 = p[0], y0 = p[1], lambda0 = lambda, a0 = c[0], b0 = c[1], c0 = c[2], maxDepth, stream);
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stream.point(x0, y0);
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}
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function lineEnd() {
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resampleStream.point = point;
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stream.lineEnd();
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}
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function ringStart() {
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lineStart();
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resampleStream.point = ringPoint;
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resampleStream.lineEnd = ringEnd;
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}
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function ringPoint(lambda, phi) {
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linePoint(lambda00 = lambda, phi), x00 = x0, y00 = y0, a00 = a0, b00 = b0, c00 = c0;
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resampleStream.point = linePoint;
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}
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function ringEnd() {
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resampleLineTo(x0, y0, lambda0, a0, b0, c0, x00, y00, lambda00, a00, b00, c00, maxDepth, stream);
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resampleStream.lineEnd = lineEnd;
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lineEnd();
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}
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return resampleStream;
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};
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} |