295 lines
7.1 KiB
JavaScript
295 lines
7.1 KiB
JavaScript
// bad stuff
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function find_chords(chords, n) {
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return chords.filter((c) => c[0].id === n.id || c[1].id === n.id);
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}
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function find_neighbours(chords, n) {
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const c = find_chords(chords, n);
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return c.map((c) => c[0].id === n.id ? c[1] : c[0])
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}
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// for a list of pairs [n1, n2] (these are nodes which share a common angle
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// from a center), find all the groups of nodes which don't appear in a pair
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// together
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function partition_nodes(pairs) {
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let groups = [];
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const seen = new Set();
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for( const pair of pairs ) {
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// both nodes are in a group already
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if( seen.has(pair[0]) && seen.has(pair[1]) ) {
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continue;
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}
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let already = false;
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// check if either node is already in a group
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for( const group of groups ) {
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if( group.has(pair[0]) ) {
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group.add(pair[1]);
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seen.add(pair[1]);
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already = true;
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continue;
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} else if( group.has(pair[1]) ) {
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group.has(pair[0]);
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seen.has(pair[0]);
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already = true;
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continue;
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}
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}
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// if neither of the pair was in a former group, start a new group
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if( !already ) {
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groups.push(new Set(pair));
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}
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// collapse any groups which now have common elements
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groups = collapse_groups(groups);
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}
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return groups;
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}
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// given a list of groups, if any have common elements, collapse them
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function collapse_groups(groups) {
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const new_groups = [ ];
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for( group of groups ) {
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let collapsed = false;
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for( new_group of new_groups ) {
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const i = intersection(group, new_group);
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if( i.size > 0 ) {
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for( const e of group ) {
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new_group.add(e);
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}
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collapsed = true;
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break;
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}
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}
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if( !collapsed ) {
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new_groups.push(new Set(group));
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}
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}
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return new_groups;
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}
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function intersection(s1, s2) {
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const i = new Set();
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for( const e of s1 ) {
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if( s2.has(e) ) {
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i.add(e)
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}
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}
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return i;
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}
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function union(s1, s2) {
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const u = new Set(s1);
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for( const e of s2 ) {
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u.add(e);
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}
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return u;
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}
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function vector_angle(n1, n2, n3) {
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const v1 = new THREE.Vector4(n1.x, n1.y, n1.z, n1.w);
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const v2 = new THREE.Vector4(n2.x, n2.y, n2.z, n2.w);
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const v3 = new THREE.Vector4(n3.x, n3.y, n3.z, n3.w);
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v2.sub(v1);
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v3.sub(v1);
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const dp = v2.dot(v3);
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return Math.acos(dp / ( v2.length() * v3.length()));
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}
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function neighbour_angles_orig(chords, n) {
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const ns = find_neighbours(chords, n);
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const angles = {};
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for( let i = 0; i < ns.length - 1; i++ ) {
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for( let j = i + 1; j < ns.length; j++ ) {
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const n2 = ns[i];
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const n3 = ns[j];
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const a = THREE.MathUtils.radToDeg(vector_angle(n, n2, n3));
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const af = (a).toFixed(3);
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if( ! (af in angles) ) {
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angles[af] = [];
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}
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angles[af].push([n2.id, n3.id]);
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}
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}
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return angles;
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}
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function neighbour_angles(chords, n, angle) {
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const ns = find_neighbours(chords, n);
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const pairs = [];
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for( let i = 0; i < ns.length - 1; i++ ) {
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for( let j = i + 1; j < ns.length; j++ ) {
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const n2 = ns[i];
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const n3 = ns[j];
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const a = THREE.MathUtils.radToDeg(vector_angle(n, n2, n3));
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const af = (a).toFixed(3);
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if( af === angle ) {
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pairs.push([n2.id, n3.id]);
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}
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}
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}
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return pairs;
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}
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function make_120_partition(nodes, n) {
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const chords = find_all_chords(nodes);
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const chord3 = chords["1.74806"]; // these are edges of the 600-cells;
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const pairs60 = neighbour_angles(chord3, n, "60.000");
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const icosas = partition_nodes(pairs60);
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n.label = 1;
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const angles = icosa_nodes(nodes, icosas[0]);
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label_120_partition_r(nodes, chord3, 1, n, angles);
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}
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// recursive function to label a single 600-cell vertex partition of the
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// 120-cell by following icosahedral nets
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// this doesn't work! completely - labels only 108-112
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function label_120_partition_r(nodes, chords, label, origin, neighbours) {
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console.log(`label_120_partition_r ${origin.id}`);
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console.log(neighbours.map((n) => n.id).join(', '));
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// first try to label everything
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const unlabelled = [];
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for( const n of neighbours ) {
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if( n.label === 0 ) {
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console.log(`Labelled ${n.id} ${label}`);
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n.label = label;
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unlabelled.push(n);
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} else if( n.label !== label ) {
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console.log(`node ${n.id} is already in group ${n.label}`);
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//return false;
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}
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}
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for( const n of unlabelled ) {
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// the angles represent two icosahedral pyramids - partition them and
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// pick the one which is at 60 to the edge we arrived on
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//console.log(`looking for more neighbors for ${n}`);
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const pairs60 = neighbour_angles(chords, n, "60.000");
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const icosas = partition_nodes(pairs60);
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const icosa = choose_icosa(nodes, origin, n, icosas);
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const icosa_n = icosa_nodes(nodes, icosa);
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console.log(`recursing to ${nice_icosa(nodes,icosa)}`);
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return label_120_partition_r(nodes, chords, label, n, icosa_n);
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}
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}
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// given a pair of icosa-sets, pick the one which is at the right angle to
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// the incoming vector
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function choose_icosa(nodes, origin, n1, icosas) {
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for( const icosa of icosas ) {
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const inodes = icosa_nodes(nodes, icosa);
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const a60 = inodes.map((ni) => {
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const a = THREE.MathUtils.radToDeg(vector_angle(n1, origin, ni));
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return a.toFixed(3);
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});
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if( a60.filter((a) => a === "60.000").length > 0 ) {
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return icosa;
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}
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}
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console.log("No icosa found!");
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return undefined;
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}
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function icosa_nodes(nodes, icosa) {
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return Array.from(icosa).map((nid) => node_by_id(nodes, nid)).sort((a, b) => a.id - b.id);
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}
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function node_by_id(nodes, nid) {
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const ns = nodes.filter((n) => n.id === nid);
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return ns[0];
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}
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function enumerate_icosas(nodes) {
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const chords = find_all_chords(nodes);
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const chord3 = chords["1.74806"]; // these are edges of the 600-cells;
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for( const n of nodes ) {
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const pairs60 = neighbour_angles(chord3, n, "60.000");
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const icosas = partition_nodes(pairs60);
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for( const icosa of icosas ) {
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const inodes = icosa_nodes(nodes, icosa);
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console.log(icosa_to_csv(n.id, inodes).join(','));
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}
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}
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}
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function icosa_to_csv(nid, icosa) {
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const cols = [ nid ];
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const ia = icosa.map((n) => n.id);
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for( let i = 1; i < 601; i++ ) {
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if( ia.includes(i) ) {
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cols.push(i);
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} else {
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cols.push('')
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}
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}
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return cols;
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}
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function start_icosas(nodes, chords, origin) {
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const pairs60 = neighbour_angles(chords, origin, "60.000");
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return partition_nodes(pairs60).map((i) => nice_icosa(nodes, i));
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}
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function next_icosa(nodes, chords, origin, nid) {
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const n = node_by_id(nodes, nid);
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const pairs60 = neighbour_angles(chords, n, "60.000");
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const icosas = partition_nodes(pairs60);
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const icosa = choose_icosa(nodes, origin, n, icosas);
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return nice_icosa(nodes, icosa);
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}
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function nice_icosa(nodes, icosa) {
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return icosa_nodes(nodes, icosa).map((n) => n.id).join(', ');
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}
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function find_by_chord(nodesid, n, d) {
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const EPSILON = 0.02;
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return Object.keys(nodesid).filter((n1) => {
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const d2 = dist2(nodesid[n1], nodesid[n]);
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return Math.abs(d2 - d ** 2) < EPSILON;
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});
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}
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function has_chord(n1, n2, d) {
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const d2 = dist2(n1, n2);
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const EPSILON = 0.01;
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return Math.abs(d2 - d ** 2) < EPSILON;
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}
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function find_all_chords(nodes) {
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const chords = {};
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for( let i = 0; i < nodes.length - 1; i++ ) {
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for( let j = i + 1; j < nodes.length; j++ ) {
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const n1 = nodes[i];
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const n2 = nodes[j];
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const chord = Math.sqrt(dist2(n1, n2)).toFixed(5);
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if( !(chord in chords) ) {
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chords[chord] = [];
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}
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chords[chord].push([n1, n2]);
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}
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}
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return chords;
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}
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