336 lines
8.3 KiB
JavaScript
336 lines
8.3 KiB
JavaScript
/// S2 Geometry functions
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// the regional scoreboard is based on a level 6 S2 Cell
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// - https://docs.google.com/presentation/d/1Hl4KapfAENAOf4gv-pSngKwvS_jwNVHRPZTTDzXXn6Q/view?pli=1#slide=id.i22
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// at the time of writing there's no actual API for the intel map to retrieve scoreboard data,
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// but it's still useful to plot the score cells on the intel map
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// the S2 geometry is based on projecting the earth sphere onto a cube, with some scaling of face coordinates to
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// keep things close to approximate equal area for adjacent cells
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// to convert a lat,lng into a cell id:
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// - convert lat,lng to x,y,z
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// - convert x,y,z into face,u,v
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// - u,v scaled to s,t with quadratic formula
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// - s,t converted to integer i,j offsets
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// - i,j converted to a position along a Hubbert space-filling curve
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// - combine face,position to get the cell id
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//NOTE: compared to the google S2 geometry library, we vary from their code in the following ways
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// - cell IDs: they combine face and the hilbert curve position into a single 64 bit number. this gives efficient space
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// and speed. javascript doesn't have appropriate data types, and speed is not cricical, so we use
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// as [face,[bitpair,bitpair,...]] instead
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// - i,j: they always use 30 bits, adjusting as needed. we use 0 to (1<<level)-1 instead
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// (so GetSizeIJ for a cell is always 1)
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(function(exports) {
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'use strict';
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var S2 = exports.S2 = {};
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var LatLngToXYZ = function(latLng) {
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var d2r = S2.L.LatLng.DEG_TO_RAD;
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var phi = latLng.lat*d2r;
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var theta = latLng.lng*d2r;
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var cosphi = Math.cos(phi);
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return [Math.cos(theta)*cosphi, Math.sin(theta)*cosphi, Math.sin(phi)];
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};
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var XYZToLatLng = function(xyz) {
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var r2d = S2.L.LatLng.RAD_TO_DEG;
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var lat = Math.atan2(xyz[2], Math.sqrt(xyz[0]*xyz[0]+xyz[1]*xyz[1]));
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var lng = Math.atan2(xyz[1], xyz[0]);
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return S2.L.LatLng(lat*r2d, lng*r2d);
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};
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var largestAbsComponent = function(xyz) {
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var temp = [Math.abs(xyz[0]), Math.abs(xyz[1]), Math.abs(xyz[2])];
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if (temp[0] > temp[1]) {
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if (temp[0] > temp[2]) {
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return 0;
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} else {
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return 2;
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}
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} else {
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if (temp[1] > temp[2]) {
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return 1;
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} else {
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return 2;
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}
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}
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};
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var faceXYZToUV = function(face,xyz) {
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var u,v;
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switch (face) {
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case 0: u = xyz[1]/xyz[0]; v = xyz[2]/xyz[0]; break;
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case 1: u = -xyz[0]/xyz[1]; v = xyz[2]/xyz[1]; break;
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case 2: u = -xyz[0]/xyz[2]; v = -xyz[1]/xyz[2]; break;
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case 3: u = xyz[2]/xyz[0]; v = xyz[1]/xyz[0]; break;
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case 4: u = xyz[2]/xyz[1]; v = -xyz[0]/xyz[1]; break;
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case 5: u = -xyz[1]/xyz[2]; v = -xyz[0]/xyz[2]; break;
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default: throw {error: 'Invalid face'};
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}
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return [u,v];
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};
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var XYZToFaceUV = function(xyz) {
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var face = largestAbsComponent(xyz);
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if (xyz[face] < 0) {
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face += 3;
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}
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var uv = faceXYZToUV (face,xyz);
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return [face, uv];
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};
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var FaceUVToXYZ = function(face,uv) {
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var u = uv[0];
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var v = uv[1];
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switch (face) {
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case 0: return [ 1, u, v];
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case 1: return [-u, 1, v];
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case 2: return [-u,-v, 1];
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case 3: return [-1,-v,-u];
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case 4: return [ v,-1,-u];
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case 5: return [ v, u,-1];
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default: throw {error: 'Invalid face'};
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}
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};
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var singleSTtoUV = function(st) {
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if (st >= 0.5) {
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return (1/3.0) * (4*st*st - 1);
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} else {
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return (1/3.0) * (1 - (4*(1-st)*(1-st)));
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}
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};
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var STToUV = function(st) {
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return [singleSTtoUV(st[0]), singleSTtoUV(st[1])];
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};
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var singleUVtoST = function(uv) {
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if (uv >= 0) {
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return 0.5 * Math.sqrt (1 + 3*uv);
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} else {
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return 1 - 0.5 * Math.sqrt (1 - 3*uv);
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}
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};
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var UVToST = function(uv) {
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return [singleUVtoST(uv[0]), singleUVtoST(uv[1])];
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};
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var STToIJ = function(st,order) {
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var maxSize = (1<<order);
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var singleSTtoIJ = function(st) {
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var ij = Math.floor(st * maxSize);
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return Math.max(0, Math.min(maxSize-1, ij));
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};
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return [singleSTtoIJ(st[0]), singleSTtoIJ(st[1])];
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};
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var IJToST = function(ij,order,offsets) {
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var maxSize = (1<<order);
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return [
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(ij[0]+offsets[0])/maxSize,
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(ij[1]+offsets[1])/maxSize
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];
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};
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// hilbert space-filling curve
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// based on http://blog.notdot.net/2009/11/Damn-Cool-Algorithms-Spatial-indexing-with-Quadtrees-and-Hilbert-Curves
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// note: rather then calculating the final integer hilbert position, we just return the list of quads
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// this ensures no precision issues whth large orders (S3 cell IDs use up to 30), and is more
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// convenient for pulling out the individual bits as needed later
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var pointToHilbertQuadList = function(x,y,order) {
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var hilbertMap = {
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'a': [ [0,'d'], [1,'a'], [3,'b'], [2,'a'] ],
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'b': [ [2,'b'], [1,'b'], [3,'a'], [0,'c'] ],
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'c': [ [2,'c'], [3,'d'], [1,'c'], [0,'b'] ],
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'd': [ [0,'a'], [3,'c'], [1,'d'], [2,'d'] ]
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};
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var currentSquare='a';
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var positions = [];
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for (var i=order-1; i>=0; i--) {
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var mask = 1<<i;
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var quad_x = x&mask ? 1 : 0;
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var quad_y = y&mask ? 1 : 0;
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var t = hilbertMap[currentSquare][quad_x*2+quad_y];
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positions.push(t[0]);
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currentSquare = t[1];
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}
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return positions;
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};
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// S2Cell class
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S2.S2Cell = function(){};
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//static method to construct
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S2.S2Cell.FromLatLng = function(latLng,level) {
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var xyz = LatLngToXYZ(latLng);
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var faceuv = XYZToFaceUV(xyz);
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var st = UVToST(faceuv[1]);
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var ij = STToIJ(st,level);
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return S2.S2Cell.FromFaceIJ (faceuv[0], ij, level);
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};
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S2.S2Cell.FromFaceIJ = function(face,ij,level) {
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var cell = new S2.S2Cell();
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cell.face = face;
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cell.ij = ij;
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cell.level = level;
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return cell;
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};
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S2.S2Cell.prototype.toString = function() {
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return 'F'+this.face+'ij['+this.ij[0]+','+this.ij[1]+']@'+this.level;
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};
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S2.S2Cell.prototype.getLatLng = function() {
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var st = IJToST(this.ij,this.level, [0.5,0.5]);
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var uv = STToUV(st);
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var xyz = FaceUVToXYZ(this.face, uv);
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return XYZToLatLng(xyz);
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};
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S2.S2Cell.prototype.getCornerLatLngs = function() {
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var result = [];
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var offsets = [
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[ 0.0, 0.0 ],
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[ 0.0, 1.0 ],
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[ 1.0, 1.0 ],
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[ 1.0, 0.0 ]
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];
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for (var i=0; i<4; i++) {
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var st = IJToST(this.ij, this.level, offsets[i]);
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var uv = STToUV(st);
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var xyz = FaceUVToXYZ(this.face, uv);
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result.push ( XYZToLatLng(xyz) );
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}
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return result;
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};
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S2.S2Cell.prototype.getFaceAndQuads = function() {
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var quads = pointToHilbertQuadList(this.ij[0], this.ij[1], this.level);
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return [this.face,quads];
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};
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S2.S2Cell.prototype.getNeighbors = function() {
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var fromFaceIJWrap = function(face,ij,level) {
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var maxSize = (1<<level);
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if (ij[0]>=0 && ij[1]>=0 && ij[0]<maxSize && ij[1]<maxSize) {
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// no wrapping out of bounds
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return S2.S2Cell.FromFaceIJ(face,ij,level);
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} else {
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// the new i,j are out of range.
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// with the assumption that they're only a little past the borders we can just take the points as
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// just beyond the cube face, project to XYZ, then re-create FaceUV from the XYZ vector
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var st = IJToST(ij,level,[0.5,0.5]);
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var uv = STToUV(st);
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var xyz = FaceUVToXYZ(face,uv);
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var faceuv = XYZToFaceUV(xyz);
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face = faceuv[0];
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uv = faceuv[1];
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st = UVToST(uv);
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ij = STToIJ(st,level);
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return S2.S2Cell.FromFaceIJ (face, ij, level);
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}
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};
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var face = this.face;
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var i = this.ij[0];
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var j = this.ij[1];
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var level = this.level;
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return [
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fromFaceIJWrap(face, [i-1,j], level),
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fromFaceIJWrap(face, [i,j-1], level),
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fromFaceIJWrap(face, [i+1,j], level),
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fromFaceIJWrap(face, [i,j+1], level)
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];
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};
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})('undefined' !== typeof window ? window : module.exports);
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(function (exports) {
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'use strict';
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// Adapted from Leafletjs https://searchcode.com/codesearch/view/42525008/
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var L = {};
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var S2 = exports.S2;
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if (!exports.L) {
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exports.L = L;
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}
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S2.L = L;
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L.LatLng = function (/*Number*/ rawLat, /*Number*/ rawLng, /*Boolean*/ noWrap) {
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var lat = parseFloat(rawLat, 10);
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var lng = parseFloat(rawLng, 10);
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if (isNaN(lat) || isNaN(lng)) {
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throw new Error('Invalid LatLng object: (' + rawLat + ', ' + rawLng + ')');
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}
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if (noWrap !== true) {
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lat = Math.max(Math.min(lat, 90), -90); // clamp latitude into -90..90
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lng = (lng + 180) % 360 + ((lng < -180 || lng === 180) ? 180 : -180); // wrap longtitude into -180..180
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}
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return { lat: lat, lng: lng };
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};
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L.LatLng.DEG_TO_RAD = Math.PI / 180;
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L.LatLng.RAD_TO_DEG = 180 / Math.PI;
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})('undefined' !== typeof window ? window : module.exports);
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