Improves method for getting child quad tile at position

Author: mzschwartz5

packages/engine/Source/Scene/QuadtreePrimitive.js

@@ -564,7 +564,7 @@ function selectTilesForRendering(primitive, frameState) {
     }
   });
 
-  levelZeroTiles.forEach((tile) => tile._updateCustomData());
+  levelZeroTiles.forEach((tile) => tile.updateCustomData());
   customDataAdded.length = 0;
   customDataRemoved.length = 0;
 
@@ -721,7 +721,7 @@ function visitTile(
   ++debug.tilesVisited;
 
   primitive._tileReplacementQueue.markTileRendered(tile);
-  tile._updateCustomData();
+  tile.updateCustomData();
 
   if (tile.level > debug.maxDepthVisited) {
     debug.maxDepthVisited = tile.level;

packages/engine/Source/Scene/QuadtreeTile.js

@@ -313,7 +313,7 @@ QuadtreeTile.prototype.clearPositionCache = function () {
   }
 };
 
-QuadtreeTile.prototype._updateCustomData = function () {
+QuadtreeTile.prototype.updateCustomData = function () {
   const added = this._addedCustomData;
   const removed = this._removedCustomData;
   if (added.length === 0 && removed.length === 0) {
@@ -342,7 +342,7 @@ QuadtreeTile.prototype._updateCustomData = function () {
   this._removedCustomData.length = 0;
 };
 
-const centerScratch = new Cartographic();
+const splitPointScratch = new Cartographic();
 
 /**
  * Determines which child tile that contains the specified position. Assumes the position is within
@@ -353,9 +353,16 @@ const centerScratch = new Cartographic();
  * @returns {QuadtreeTile} The child tile that contains the position.
  */
 function childTileAtPosition(tile, positionCartographic) {
-  const center = Rectangle.center(tile.rectangle, centerScratch);
-  const x = positionCartographic.longitude >= center.longitude ? 1 : 0;
-  const y = positionCartographic.latitude < center.latitude ? 1 : 0;
+  // Can't assume that a given tiling scheme divides a parent into four tiles at its rectangle's center.
+  // But we can safely take any child tile's rectangle and take its center-facing corner as the parent's split point.
+  const nwChildRectangle = tile.northwestChild.rectangle;
+  const tileSplitPoint = Rectangle.southeast(
+    nwChildRectangle,
+    splitPointScratch,
+  );
+
+  const x = positionCartographic.longitude >= tileSplitPoint.longitude ? 1 : 0;
+  const y = positionCartographic.latitude < tileSplitPoint.latitude ? 1 : 0;
 
   switch (y * 2 + x) {
     case 0:

packages/engine/Specs/Scene/QuadtreeTileSpec.js

@@ -458,4 +458,53 @@ describe("Scene/QuadtreeTile", function () {
       expect(cachedData).toEqual(dummyPosition);
     });
   });
+
+  describe("updateCustomData", function () {
+    function addAndRemoveCustomData(tilingScheme) {
+      const tile = new QuadtreeTile({
+        level: 0,
+        x: 0,
+        y: 0,
+        tilingScheme: tilingScheme,
+      });
+
+      const child = tile.northwestChild;
+      const centerCartographic = Rectangle.center(child.rectangle);
+
+      const data = {
+        positionCartographic: centerCartographic,
+      };
+
+      tile._addedCustomData.push(data);
+      tile.updateCustomData();
+
+      expect(tile.customData.has(data)).toBe(true);
+      expect(tile._addedCustomData.length).toBe(0);
+      expect(child._addedCustomData.length).toBe(1);
+      expect(child._addedCustomData[0]).toBe(data);
+
+      child.updateCustomData();
+      expect(child.customData.has(data)).toBe(true);
+
+      // Now remove the data from the parent tile.
+      tile._removedCustomData.push(data);
+      tile.updateCustomData();
+
+      expect(tile.customData.has(data)).toBe(false);
+      expect(tile._removedCustomData.length).toBe(0);
+      expect(child._removedCustomData.length).toBe(1);
+      expect(child._removedCustomData[0]).toBe(data);
+
+      child.updateCustomData();
+      expect(child.customData.has(data)).toBe(false);
+    }
+
+    it("can add and remove custom data when tiling scheme is GeographicTilingScheme", function () {
+      addAndRemoveCustomData(new GeographicTilingScheme());
+    });
+
+    it("can add and remove custom data when tiling scheme is WebMercatorTilingScheme", function () {
+      addAndRemoveCustomData(new WebMercatorTilingScheme());
+    });
+  });
 });