Fixing refinement of mixed empty and non-empty tiles

CHANGES.md

@@ -6,6 +6,7 @@
 
 ##### Fixes :wrench:
 
+- Fixed a bug with where a mix of empty and non-empty tiles were not refining. [#9356](https://github.com/CesiumGS/cesium/issues/9356)
 - Fixed a bug affecting voxel shader compilation in WebGL1 contexts. [#11798](https://github.com/CesiumGS/cesium/pull/11798)
 - Fixed a bug where legacy B3DM files that contained glTF 1.0 data that used a `CONSTANT` technique in the `KHR_material_common` extension and only defined ambient- or emissive textures (but no diffuse textures) showed up without any texture [#11825](https://github.com/CesiumGS/cesium/pull/11825)
 

CONTRIBUTORS.md

@@ -163,6 +163,7 @@ See [CONTRIBUTING.md](CONTRIBUTING.md) for details on how to contribute to Cesiu
   - [Mark Dane](https://github.com/angrycat9000)
   - [jjspace](https://github.com/jjspace)
   - [Siddhesh Ranade](https://github.com/siddheshranade)
+  - [Adam Morris](https://github.com/weegeekps)
 - [Northrop Grumman](http://www.northropgrumman.com)
   - [Joseph Stein](https://github.com/nahgrin)
 - [EOX IT Services GmbH](https://eox.at)

packages/engine/Source/Scene/Cesium3DTilesetBaseTraversal.js

@@ -271,12 +271,10 @@ function executeEmptyTraversal(root, frameState) {
 
     // Only traverse if the tile is empty - traversal stops at descendants with content
     const traverse = !tile.hasRenderableContent && canTraverse(tile);
-    const emptyLeaf = !tile.hasRenderableContent && tile.children.length === 0;
 
     // Traversal stops but the tile does not have content yet
     // There will be holes if the parent tries to refine to its children, so don't refine
-    // One exception: a parent may refine even if one of its descendants is an empty leaf
-    if (!traverse && !tile.contentAvailable && !emptyLeaf) {
+    if (!traverse && !tile.contentAvailable) {
       allDescendantsLoaded = false;
     }
 
@@ -295,7 +293,7 @@ function executeEmptyTraversal(root, frameState) {
     }
   }
 
-  return allDescendantsLoaded;
+  return root.hasEmptyContent || allDescendantsLoaded;
 }
 
 export default Cesium3DTilesetBaseTraversal;

packages/engine/Specs/Scene/Cesium3DTilesetSpec.js

@@ -1335,29 +1335,6 @@ describe(
       });
     });
 
-    it("replacement refinement - selects upwards when traversal stops at empty tile", function () {
-      // No children have content, but all grandchildren have content
-      //
-      //          C
-      //      E       E
-      //    C   C   C   C
-      //
-      return Cesium3DTilesTester.loadTileset(
-        scene,
-        tilesetReplacement1Url
-      ).then(function (tileset) {
-        tileset.root.geometricError = 90;
-        setZoom(80);
-        scene.renderForSpecs();
-
-        const statistics = tileset._statistics;
-        expect(statistics.selected).toEqual(1);
-        expect(statistics.visited).toEqual(3);
-        expect(isSelected(tileset, tileset.root)).toBe(true);
-        return Cesium3DTilesTester.waitForTilesLoaded(scene, tileset);
-      });
-    });
-
     it("replacement refinement - selects root when sse is not met and subtree is not refinable (1)", function () {
       // No children have content, but all grandchildren have content
       //
@@ -1379,7 +1356,6 @@ describe(
 
         // Even though root's children are loaded, the grandchildren need to be loaded before it becomes refinable
         expect(numberOfChildrenWithoutContent(root)).toEqual(0); // Children are loaded
-        expect(statistics.numberOfCommands).toEqual(1); // No stencil or backface commands; no mixed content
         expect(statistics.numberOfPendingRequests).toEqual(4); // Loading grandchildren
 
         return Cesium3DTilesTester.waitForTilesLoaded(scene, tileset).then(