Terrain availability race condition

CHANGES.md

@@ -1,5 +1,13 @@
 # Change Log
 
+### 1.106 - 2023-06-01
+
+#### @cesium/engine
+
+##### Fixes :wrench:
+
+- Fixed a race condition when loading cut-out terrain. [#11296](https://github.com/CesiumGS/cesium/pull/11296)
+
 ### 1.105.2 - 2023-05-15
 
 - This is an npm-only release to fix a dependency issue published in 1.105.1.

Specs/Data/CesiumTerrainTileJson/ParentAvailability.tile.json

@@ -0,0 +1,36 @@
+{
+    "tilejson": "2.1.0",
+    "format" : "quantized-mesh-1.0",
+    "version" : "1.0.0",
+    "scheme" : "tms",
+    "attribution" : "This amazing data is courtesy The Amazing Data Source!",
+    "tiles" : [
+        "{z}/{x}/{y}.terrain?v={version}"
+    ],
+    "extensions": [
+        "watermask",
+        "metadata",
+        "octvertexnormals"
+    ],
+    "metadataAvailability": 10,
+    "minzoom": 0,
+    "maxzoom": 13,
+    "available" : [
+        [
+            {
+                "startX" : 0,
+                "startY" : 0,
+                "endX" : 1,
+                "endY" : 0
+            }
+        ],
+        [
+            {
+                "startX" : 0,
+                "startY" : 0,
+                "endX" : 3,
+                "endY" : 1
+            }
+        ]
+    ]
+}

Specs/Data/CesiumTerrainTileJson/ParentUrlAvailability.tile.json

@@ -0,0 +1,38 @@
+{
+    "tilejson": "2.1.0",
+    "format" : "quantized-mesh-1.0",
+    "version" : "1.0.0",
+    "scheme" : "tms",
+    "attribution" : "This is a child tileset!",
+    "tiles" : [
+        "{z}/{x}/{y}.terrain?v={version}"
+    ],
+    "extensions" : [
+        "watermask",
+        "metadata",
+        "octvertexnormals"
+    ],
+    "metadataAvailability": 10,
+    "minzoom": 0,
+    "maxzoom": 13,
+    "available" : [
+        [
+            {
+                "startX" : 0,
+                "startY" : 0,
+                "endX" : 1,
+                "endY" : 0
+            }
+        ],
+        [
+            {
+                "startX" : 0,
+                "startY" : 0,
+                "endX" : 2,
+                "endY" : 1
+            }
+        ]
+    ],
+    "parentUrl": "./"
+}
+

packages/engine/Source/Core/CesiumTerrainProvider.js

@@ -901,6 +901,8 @@ CesiumTerrainProvider.prototype.requestTileGeometry = function (
   const layers = this._layers;
   let layerToUse;
   const layerCount = layers.length;
+  let unknownAvailability = false;
+  let availabilityPromise = Promise.resolve();
 
   if (layerCount === 1) {
     // Optimized path for single layers
@@ -915,9 +917,32 @@ CesiumTerrainProvider.prototype.requestTileGeometry = function (
         layerToUse = layer;
         break;
       }
+
+      const availabilityUnloaded = checkLayer(
+        this,
+        x,
+        y,
+        level,
+        layer,
+        i === 0
+      );
+      if (availabilityUnloaded.result) {
+        // We can't know yet since the availability is not yet loaded
+        unknownAvailability = true;
+        availabilityPromise = availabilityPromise.then(
+          () => availabilityUnloaded.promise
+        );
+      }
     }
   }
 
+  if (!defined(layerToUse) && unknownAvailability) {
+    // Try again when availability data is ready– Otherwise the tile will be marked as failed and never re-requested
+    return availabilityPromise.then(() =>
+      this.requestTileGeometry(x, y, level, request)
+    );
+  }
+
   return requestTileGeometry(this, x, y, level, layerToUse, request);
 };
 

packages/engine/Specs/Core/CesiumTerrainProviderSpec.js

@@ -133,6 +133,45 @@ describe("Core/CesiumTerrainProvider", function () {
     );
   }
 
+  function returnParentUrlTileJsonWithMetadataAvailability() {
+    const paths = [
+      "Data/CesiumTerrainTileJson/ParentUrlAvailability.tile.json",
+      "Data/CesiumTerrainTileJson/ParentAvailability.tile.json",
+    ];
+    let i = 0;
+    const oldLoad = Resource._Implementations.loadWithXhr;
+    Resource._Implementations.loadWithXhr = function (
+      url,
+      responseType,
+      method,
+      data,
+      headers,
+      deferred,
+      overrideMimeType
+    ) {
+      if (url.indexOf("layer.json") >= 0) {
+        Resource._DefaultImplementations.loadWithXhr(
+          paths[i++],
+          responseType,
+          method,
+          data,
+          headers,
+          deferred
+        );
+      } else {
+        return oldLoad(
+          url,
+          responseType,
+          method,
+          data,
+          headers,
+          deferred,
+          overrideMimeType
+        );
+      }
+    };
+  }
+
   async function waitForTile(level, x, y, requestNormals, requestWaterMask, f) {
     const terrainProvider = await CesiumTerrainProvider.fromUrl("made/up/url", {
       requestVertexNormals: requestNormals,
@@ -899,6 +938,43 @@ describe("Core/CesiumTerrainProvider", function () {
       expect(terrainProvider.availability.isTileAvailable(1, 0, 0)).toBe(true);
     });
 
+    it("provides QuantizedMeshTerrainData with multiple layers and with Metadata availability ", async function () {
+      Resource._Implementations.loadWithXhr = function (
+        url,
+        responseType,
+        method,
+        data,
+        headers,
+        deferred,
+        overrideMimeType
+      ) {
+        Resource._DefaultImplementations.loadWithXhr(
+          "Data/CesiumTerrainTileJson/tile.metadataavailability.terrain",
+          responseType,
+          method,
+          data,
+          headers,
+          deferred
+        );
+      };
+
+      returnParentUrlTileJsonWithMetadataAvailability();
+
+      const terrainProvider = await CesiumTerrainProvider.fromUrl(
+        "made/up/url"
+      );
+
+      expect(terrainProvider.hasMetadata).toBe(true);
+      const layers = terrainProvider._layers;
+      expect(layers.length).toBe(2);
+
+      expect(terrainProvider.availability.isTileAvailable(1, 0, 0)).toBe(false);
+
+      const loadedData = await terrainProvider.requestTileGeometry(0, 0, 1);
+      expect(loadedData).toBeInstanceOf(QuantizedMeshTerrainData);
+      expect(terrainProvider.availability.isTileAvailable(1, 0, 0)).toBe(true);
+    });
+
     it("returns undefined if too many requests are already in progress", async function () {
       const baseUrl = "made/up/url";