use correct starting square for face #6 #8 #9

src/s2geometry.js

@@ -186,7 +186,7 @@ S2.IJToST = function(ij,order,offsets) {
 // note: rather then calculating the final integer hilbert position, we just return the list of quads
 // this ensures no precision issues whth large orders (S3 cell IDs use up to 30), and is more
 // convenient for pulling out the individual bits as needed later
-var pointToHilbertQuadList = function(x,y,order) {
+var pointToHilbertQuadList = function(x,y,order,sq) {
   var hilbertMap = {
     'a': [ [0,'d'], [1,'a'], [3,'b'], [2,'a'] ],
     'b': [ [2,'b'], [1,'b'], [3,'a'], [0,'c'] ],
@@ -194,7 +194,7 @@ var pointToHilbertQuadList = function(x,y,order) {
     'd': [ [0,'a'], [3,'c'], [1,'d'], [2,'d'] ]
   };
 
-  var currentSquare='a';
+  var currentSquare=sq||'a';
   var positions = [];
 
   for (var i=order-1; i>=0; i--) {
@@ -286,7 +286,27 @@ S2.S2Cell.prototype.getCornerLatLngs = function() {
 
 
 S2.S2Cell.prototype.getFaceAndQuads = function () {
-  var quads = pointToHilbertQuadList(this.ij[0], this.ij[1], this.level);
+  var sq;
+
+  switch(this.face) {
+    case 0:
+      /* fallthru */
+    case 2:
+      /* fallthru */
+    case 4:
+      sq = 'a';
+      break;
+
+    case 1:
+      /* fallthru */
+    case 3:
+      /* fallthru */
+    case 5:
+      sq = 'd';
+      break;
+  }
+
+  var quads = pointToHilbertQuadList(this.ij[0], this.ij[1], this.level, sq);
 
   return [this.face,quads];
 };

tests/debug.js

@@ -8,6 +8,23 @@ var lat = -43.525166;
 var lng = 172.655096;
 //var id = '8678661352471920640';
 
+var tests = [
+  [ -13.846153846153854, -41.53846153846155 ]   // face 0
+, [ -13.846153846153854, 96.92307692307692 ]    // face 1
+, [ 41.53846153846153, -124.61538461538463 ]    // face 2
+, [ -152.30769230769232, 41.53846153846153 ]    // face 3
+, [ -152.30769230769232, 69.23076923076923 ]    // face 4
+, [ -124.61538461538463, -69.23076923076924 ]   // face 5
+];
+
+tests.forEach(function (pair, i) {
+  var lat = pair[0];
+  var lng = pair[1];
+
+  console.log('');
+  console.log('');
+  console.log('FACE', i);
+
   console.log('');
   console.log('Lat/Lng');
   console.log('=', lat + ',' + lng);
@@ -16,35 +33,29 @@ console.log('=', lat + ',' + lng);
   // Lat / Lng to XYZ
   //
   var nS2LatLng = new nS2.S2LatLng(lat, lng).toPoint();
-var nXyz = [ nS2LatLng.x(), nS2LatLng.y(), nS2LatLng.z() ];
-//var oXyz = oS2.LatLngToXYZ({ lat: lat, lng: lng });
-var jXyz = jS2.LatLngToXYZ({ lat: lat, lng: lng });
+  //var nXyz = [ nS2LatLng.x(), nS2LatLng.y(), nS2LatLng.z() ];
+  //var jXyz = jS2.LatLngToXYZ({ lat: lat, lng: lng });
+  /*
   console.log('');
   console.log('XYZ');
   console.log('=', nXyz);
-//console.log('o', oXyz);
   console.log('j', jXyz);
+  */
 
 
   var nCell = new nS2.S2CellId(nS2LatLng).parent(15);
-//var oCell = oS2.S2Cell.FromLatLng({ lat: lat, lng: lng }, 15);
   var jCell = jS2.S2Cell.FromLatLng({ lat: lat, lng: lng }, 15);
+  /*
   console.log('');
   console.log('F,IJ,L');
-//console.log('=', cellN);
-//console.log('o', oCell.toString());
   console.log('j', jCell.toString());
+  */
 
   var nKey = nCell.toString();
-//var oQuad = oCell.getFaceAndQuads();
-//var oKey = oQuad[0] + '/' + oQuad[1].join('');
   var jQuad = jCell.getFaceAndQuads();
   var jKey = jQuad[0] + '/' + jQuad[1].join('');
   console.log('');
   console.log('Quadkey');
   console.log('=', nKey);
-//console.log('o', oKey);
   console.log('j', jKey);
-
-//var nCellId = new nS2.S2CellId(id);
-//console.log(nCellId.toLatLng().toString());
+});