/// S2 Geometry functions // the regional scoreboard is based on a level 6 S2 Cell // - https://docs.google.com/presentation/d/1Hl4KapfAENAOf4gv-pSngKwvS_jwNVHRPZTTDzXXn6Q/view?pli=1#slide=id.i22 // at the time of writing there's no actual API for the intel map to retrieve scoreboard data, // but it's still useful to plot the score cells on the intel map // the S2 geometry is based on projecting the earth sphere onto a cube, with some scaling of face coordinates to // keep things close to approximate equal area for adjacent cells // to convert a lat,lng into a cell id: // - convert lat,lng to x,y,z // - convert x,y,z into face,u,v // - u,v scaled to s,t with quadratic formula // - s,t converted to integer i,j offsets // - i,j converted to a position along a Hubbert space-filling curve // - combine face,position to get the cell id //NOTE: compared to the google S2 geometry library, we vary from their code in the following ways // - cell IDs: they combine face and the hilbert curve position into a single 64 bit number. this gives efficient space // and speed. javascript doesn't have appropriate data types, and speed is not cricical, so we use // as [face,[bitpair,bitpair,...]] instead // - i,j: they always use 30 bits, adjusting as needed. we use 0 to (1< temp[1]) { if (temp[0] > temp[2]) { return 0; } else { return 2; } } else { if (temp[1] > temp[2]) { return 1; } else { return 2; } } }; var faceXYZToUV = function(face,xyz) { var u,v; switch (face) { case 0: u = xyz[1]/xyz[0]; v = xyz[2]/xyz[0]; break; case 1: u = -xyz[0]/xyz[1]; v = xyz[2]/xyz[1]; break; case 2: u = -xyz[0]/xyz[2]; v = -xyz[1]/xyz[2]; break; case 3: u = xyz[2]/xyz[0]; v = xyz[1]/xyz[0]; break; case 4: u = xyz[2]/xyz[1]; v = -xyz[0]/xyz[1]; break; case 5: u = -xyz[1]/xyz[2]; v = -xyz[0]/xyz[2]; break; default: throw {error: 'Invalid face'}; break; } return [u,v]; } var XYZToFaceUV = function(xyz) { var face = largestAbsComponent(xyz); if (xyz[face] < 0) { face += 3; } uv = faceXYZToUV (face,xyz); return [face, uv]; }; var FaceUVToXYZ = function(face,uv) { var u = uv[0]; var v = uv[1]; switch (face) { case 0: return [ 1, u, v]; case 1: return [-u, 1, v]; case 2: return [-u,-v, 1]; case 3: return [-1,-v,-u]; case 4: return [ v,-1,-u]; case 5: return [ v, u,-1]; default: throw {error: 'Invalid face'}; } }; var STToUV = function(st) { var singleSTtoUV = function(st) { if (st >= 0.5) { return (1/3.0) * (4*st*st - 1); } else { return (1/3.0) * (1 - (4*(1-st)*(1-st))); } } return [singleSTtoUV(st[0]), singleSTtoUV(st[1])]; }; var UVToST = function(uv) { var singleUVtoST = function(uv) { if (uv >= 0) { return 0.5 * Math.sqrt (1 + 3*uv); } else { return 1 - 0.5 * Math.sqrt (1 - 3*uv); } } return [singleUVtoST(uv[0]), singleUVtoST(uv[1])]; }; var STToIJ = function(st,order) { var maxSize = (1<=0; i--) { var mask = 1<=0 && ij[1]>=0 && ij[0]