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| import Feature from 'ol/Feature.js';
import LineString from 'ol/geom/LineString.js';
import Map from 'ol/Map.js';
import VectorLayer from 'ol/layer/Vector.js';
import VectorSource from 'ol/source/Vector.js';
import View from 'ol/View.js';
const radius = 10e6;
const cos30 = Math.cos(Math.PI / 6);
const sin30 = Math.sin(Math.PI / 6);
const rise = radius * sin30;
const run = radius * cos30;
const triangle = new LineString([
[0, radius],
[run, -rise],
[-run, -rise],
[0, radius],
]);
const feature = new Feature(triangle);
const layer = new VectorLayer({
source: new VectorSource({
features: [feature],
}),
});
const map = new Map({
layers: [layer],
target: 'map',
view: new View({
center: [0, 0],
zoom: 1,
}),
});
function makeFractal(depth) {
const geometry = triangle.clone();
const graph = coordsToGraph(geometry.getCoordinates());
for (let i = 0; i < depth; ++i) {
let node = graph;
while (node.next) {
const next = node.next;
injectNodes(node);
node = next;
}
}
const coordinates = graphToCoords(graph);
document.getElementById('count').innerHTML = coordinates.length;
geometry.setCoordinates(coordinates);
feature.setGeometry(geometry);
}
function injectNodes(startNode) {
const endNode = startNode.next;
const start = startNode.point;
const end = startNode.next.point;
const dx = end[0] - start[0];
const dy = end[1] - start[1];
const firstNode = {
point: [start[0] + dx / 3, start[1] + dy / 3],
};
const r = Math.sqrt(dx * dx + dy * dy) / (2 * cos30);
const a = Math.atan2(dy, dx) + Math.PI / 6;
const secondNode = {
point: [start[0] + r * Math.cos(a), start[1] + r * Math.sin(a)],
};
const thirdNode = {
point: [end[0] - dx / 3, end[1] - dy / 3],
};
startNode.next = firstNode;
firstNode.next = secondNode;
secondNode.next = thirdNode;
thirdNode.next = endNode;
}
function coordsToGraph(coordinates) {
const graph = {
point: coordinates[0],
};
const length = coordinates.length;
for (let level = 0, node = graph; level < length - 1; ++level) {
node.next = {
point: coordinates[level + 1],
};
node = node.next;
}
return graph;
}
function graphToCoords(graph) {
const coordinates = [graph.point];
for (let node = graph, i = 1; node.next; node = node.next, ++i) {
coordinates[i] = node.next.point;
}
return coordinates;
}
const depthInput = document.getElementById('depth');
function update() {
makeFractal(Number(depthInput.value));
}
let updateTimer;
depthInput.onchange = function () {
window.clearTimeout(updateTimer);
updateTimer = window.setTimeout(update, 200);
};
update();
|
)
