Second round PR feedback

CHANGES.md

@@ -4,7 +4,7 @@
 
 ##### Additions :tada:
 
-- Added `Cesium3DTileset.cacheBytes` and `Cesium3DTileset.maximumCacheOverflowBytes` to better control memory usage. To replicate previous behavior, change `maximumMemoryUsage` to `cacheBytes`, and set `maximumCacheOverflowBytes = Number.MAX_VALUE`
+- Added `Cesium3DTileset.cacheBytes` and `Cesium3DTileset.maximumCacheOverflowBytes` to better control memory usage. To replicate previous behavior, convert `maximumMemoryUsage` from MB to bytes, assign the value to `cacheBytes`, and set `maximumCacheOverflowBytes = Number.MAX_VALUE`
 
 ##### Fixes :wrench:
 

packages/engine/Specs/Scene/Cesium3DTilesetSpec.js

@@ -3434,6 +3434,77 @@ describe(
     ///////////////////////////////////////////////////////////////////////////
     // Cache replacement tests
 
+    it("Unload all cached tiles not required to meet SSE using maximumMemoryUsage", function () {
+      return Cesium3DTilesTester.loadTileset(scene, tilesetUrl).then(function (
+        tileset
+      ) {
+        tileset.maximumMemoryUsage = 0;
+
+        // Render parent and four children (using additive refinement)
+        viewAllTiles();
+        scene.renderForSpecs();
+
+        const statistics = tileset._statistics;
+        expect(statistics.numberOfCommands).toEqual(5);
+        expect(statistics.numberOfTilesWithContentReady).toEqual(5); // Five loaded tiles
+        expect(tileset.totalMemoryUsageInBytes).toEqual(37200); // Specific to this tileset
+
+        // Zoom out so only root tile is needed to meet SSE.  This unloads
+        // the four children since the maximum memory usage is zero.
+        viewRootOnly();
+        scene.renderForSpecs();
+
+        expect(statistics.numberOfCommands).toEqual(1);
+        expect(statistics.numberOfTilesWithContentReady).toEqual(1);
+        expect(tileset.totalMemoryUsageInBytes).toEqual(7440); // Specific to this tileset
+
+        // Zoom back in so all four children are re-requested.
+        viewAllTiles();
+
+        return Cesium3DTilesTester.waitForTilesLoaded(scene, tileset).then(
+          function () {
+            expect(statistics.numberOfCommands).toEqual(5);
+            expect(statistics.numberOfTilesWithContentReady).toEqual(5); // Five loaded tiles
+            expect(tileset.totalMemoryUsageInBytes).toEqual(37200); // Specific to this tileset
+          }
+        );
+      });
+    });
+
+    it("Unload some cached tiles not required to meet SSE using maximumMemoryUsage", function () {
+      return Cesium3DTilesTester.loadTileset(scene, tilesetUrl).then(function (
+        tileset
+      ) {
+        tileset.maximumMemoryUsage = 0.025; // Just enough memory to allow 3 tiles to remain
+        // Render parent and four children (using additive refinement)
+        viewAllTiles();
+        scene.renderForSpecs();
+
+        const statistics = tileset._statistics;
+        expect(statistics.numberOfCommands).toEqual(5);
+        expect(statistics.numberOfTilesWithContentReady).toEqual(5); // Five loaded tiles
+
+        // Zoom out so only root tile is needed to meet SSE.  This unloads
+        // two of the four children so three tiles are still loaded (the
+        // root and two children) since the maximum memory usage is sufficient.
+        viewRootOnly();
+        scene.renderForSpecs();
+
+        expect(statistics.numberOfCommands).toEqual(1);
+        expect(statistics.numberOfTilesWithContentReady).toEqual(3);
+
+        // Zoom back in so the two children are re-requested.
+        viewAllTiles();
+
+        return Cesium3DTilesTester.waitForTilesLoaded(scene, tileset).then(
+          function () {
+            expect(statistics.numberOfCommands).toEqual(5);
+            expect(statistics.numberOfTilesWithContentReady).toEqual(5); // Five loaded tiles
+          }
+        );
+      });
+    });
+
     it("Unload all cached tiles not required to meet SSE using cacheBytes", function () {
       return Cesium3DTilesTester.loadTileset(scene, tilesetUrl).then(function (
         tileset