Allow external tilesets in multiple contents

CHANGES.md

@@ -21,6 +21,7 @@
 - Fixed type error when setting `Viewer.selectedEntity` [#12303](https://github.com/CesiumGS/cesium/issues/12303)
 - Fixed urls with https in the documentation `basemap.nationalmap.gov` [#12375](https://github.com/CesiumGS/cesium/issues/12375)
 - Fixed error in polyline when sinAngle is < 1. the value of expandWidth was too much. [#12434](https://github.com/CesiumGS/cesium/pull/12434)
+- Allow external tilesets in multiple contents. [#12440](https://github.com/CesiumGS/cesium/pull/12440)
 
 ## 1.125 - 2025-01-02
 

Specs/Data/Cesium3DTiles/MultipleContents/ExternalInMultipleContents/README.md

@@ -0,0 +1,10 @@
+# ExternalInMultipleContents
+
+A tileset that was created as a regression test for
+https://github.com/CesiumGS/cesium/issues/11960
+
+It contains a single root node with 4 contents:
+
+- The first one is a GLB of a red unit cube
+- The remaining three are external tilesets, containing
+  a green, blue, and white unit cube, respectively

Specs/Data/Cesium3DTiles/MultipleContents/ExternalInMultipleContents/externalB.json

@@ -0,0 +1,17 @@
+{
+  "asset" : {
+    "version" : "1.1"
+  },
+  "geometricError" : 4096.0,
+  "root" : {
+    "boundingVolume" : {
+      "box" : [ 0.5, -0.5, 0.5, 0.5, 0.0, 0.0, 0.0, 0.5, 0.0, 0.0, 0.0, 0.5 ]
+    },
+    "geometricError" : 2048.0,
+    "refine" : "ADD",
+    "transform" : [ 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 1.0, 0.0, 0.0, 1.0 ],
+    "content" : {
+      "uri" : "contentB.glb"
+    }
+  }
+}

Specs/Data/Cesium3DTiles/MultipleContents/ExternalInMultipleContents/externalC.json

@@ -0,0 +1,17 @@
+{
+  "asset" : {
+    "version" : "1.1"
+  },
+  "geometricError" : 4096.0,
+  "root" : {
+    "boundingVolume" : {
+      "box" : [ 0.5, -0.5, 0.5, 0.5, 0.0, 0.0, 0.0, 0.5, 0.0, 0.0, 0.0, 0.5 ]
+    },
+    "geometricError" : 2048.0,
+    "refine" : "ADD",
+    "transform" : [ 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 1.0, 0.0, 1.0 ],
+    "content" : {
+      "uri" : "contentC.glb"
+    }
+  }
+}

Specs/Data/Cesium3DTiles/MultipleContents/ExternalInMultipleContents/externalD.json

@@ -0,0 +1,17 @@
+{
+  "asset" : {
+    "version" : "1.1"
+  },
+  "geometricError" : 4096.0,
+  "root" : {
+    "boundingVolume" : {
+      "box" : [ 0.5, -0.5, 0.5, 0.5, 0.0, 0.0, 0.0, 0.5, 0.0, 0.0, 0.0, 0.5 ]
+    },
+    "geometricError" : 2048.0,
+    "refine" : "ADD",
+    "transform" : [ 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 1.0, 1.0, 0.0, 1.0 ],
+    "content" : {
+      "uri" : "contentD.glb"
+    }
+  }
+}

Specs/Data/Cesium3DTiles/MultipleContents/ExternalInMultipleContents/tileset.json

@@ -0,0 +1,40 @@
+{
+  "asset": {
+    "version": "1.1"
+  },
+  "geometricError": 4096,
+  "root": {
+    "boundingVolume": {
+      "box": [
+        1,
+        0,
+        0.5,
+        1,
+        0,
+        0,
+        0,
+        1,
+        0,
+        0,
+        0,
+        0.5
+      ]
+    },
+    "refine": "ADD",
+    "geometricError": 4096,
+    "contents": [
+      {
+        "uri": "contentA.glb"
+      },
+      {
+        "uri": "externalB.json"
+      },
+      {
+        "uri": "externalC.json"
+      },
+      {
+        "uri": "externalD.json"
+      }
+    ]
+  }
+}

Specs/Data/Cesium3DTiles/MultipleContents/OnlyExternalInMultipleContents/README.md

@@ -0,0 +1,8 @@
+# OnlyExternalInMultipleContents
+
+A tileset that was created as a regression test for
+https://github.com/CesiumGS/cesium/issues/11960
+
+It contains a single root node with 4 contents that
+are all external tilesets, each containing a GLB of
+red, green, blue, and white unit cube, respectively

Specs/Data/Cesium3DTiles/MultipleContents/OnlyExternalInMultipleContents/externalA.json

@@ -0,0 +1,17 @@
+{
+  "asset" : {
+    "version" : "1.1"
+  },
+  "geometricError" : 4096.0,
+  "root" : {
+    "boundingVolume" : {
+      "box" : [ 0.5, -0.5, 0.5, 0.5, 0.0, 0.0, 0.0, 0.5, 0.0, 0.0, 0.0, 0.5 ]
+    },
+    "geometricError" : 2048.0,
+    "refine" : "ADD",
+    "transform" : [ 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0 ],
+    "content" : {
+      "uri" : "contentA.glb"
+    }
+  }
+}

Specs/Data/Cesium3DTiles/MultipleContents/OnlyExternalInMultipleContents/externalB.json

@@ -0,0 +1,17 @@
+{
+  "asset" : {
+    "version" : "1.1"
+  },
+  "geometricError" : 4096.0,
+  "root" : {
+    "boundingVolume" : {
+      "box" : [ 0.5, -0.5, 0.5, 0.5, 0.0, 0.0, 0.0, 0.5, 0.0, 0.0, 0.0, 0.5 ]
+    },
+    "geometricError" : 2048.0,
+    "refine" : "ADD",
+    "transform" : [ 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 1.0, 0.0, 0.0, 1.0 ],
+    "content" : {
+      "uri" : "contentB.glb"
+    }
+  }
+}

Specs/Data/Cesium3DTiles/MultipleContents/OnlyExternalInMultipleContents/externalC.json

@@ -0,0 +1,17 @@
+{
+  "asset" : {
+    "version" : "1.1"
+  },
+  "geometricError" : 4096.0,
+  "root" : {
+    "boundingVolume" : {
+      "box" : [ 0.5, -0.5, 0.5, 0.5, 0.0, 0.0, 0.0, 0.5, 0.0, 0.0, 0.0, 0.5 ]
+    },
+    "geometricError" : 2048.0,
+    "refine" : "ADD",
+    "transform" : [ 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 1.0, 0.0, 1.0 ],
+    "content" : {
+      "uri" : "contentC.glb"
+    }
+  }
+}

Specs/Data/Cesium3DTiles/MultipleContents/OnlyExternalInMultipleContents/externalD.json

@@ -0,0 +1,17 @@
+{
+  "asset" : {
+    "version" : "1.1"
+  },
+  "geometricError" : 4096.0,
+  "root" : {
+    "boundingVolume" : {
+      "box" : [ 0.5, -0.5, 0.5, 0.5, 0.0, 0.0, 0.0, 0.5, 0.0, 0.0, 0.0, 0.5 ]
+    },
+    "geometricError" : 2048.0,
+    "refine" : "ADD",
+    "transform" : [ 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 1.0, 1.0, 0.0, 1.0 ],
+    "content" : {
+      "uri" : "contentD.glb"
+    }
+  }
+}

Specs/Data/Cesium3DTiles/MultipleContents/OnlyExternalInMultipleContents/tileset.json

@@ -0,0 +1,40 @@
+{
+  "asset": {
+    "version": "1.1"
+  },
+  "geometricError": 4096,
+  "root": {
+    "boundingVolume": {
+      "box": [
+        1,
+        0,
+        0.5,
+        1,
+        0,
+        0,
+        0,
+        1,
+        0,
+        0,
+        0,
+        0.5
+      ]
+    },
+    "refine": "ADD",
+    "geometricError": 4096,
+    "contents": [
+      {
+        "uri": "externalA.json"
+      },
+      {
+        "uri": "externalB.json"
+      },
+      {
+        "uri": "externalC.json"
+      },
+      {
+        "uri": "externalD.json"
+      }
+    ]
+  }
+}

packages/engine/Source/Scene/Cesium3DTile.js

@@ -319,6 +319,24 @@ function Cesium3DTile(tileset, baseResource, header, parent) {
    */
   this.hasImplicitContent = false;
 
+  /**
+   * Determines whether the tile has renderable content.
+   *
+   * The loading starts with the assumption that the tile does have
+   * renderable content, if the content is not empty.<br>
+   * <br>
+   * This turns <code>false</code> only when the tile content is loaded
+   * and turns out to be a single content that points to an external
+   * tileset or implicit content
+   * </p>
+   *
+   * @type {boolean}
+   * @readonly
+   *
+   * @private
+   */
+  this.hasRenderableContent = !hasEmptyContent;
+
   /**
    * When <code>true</code>, the tile contains content metadata from implicit tiling. This flag is set
    * for tiles transcoded by <code>Implicit3DTileContent</code>.
@@ -653,27 +671,6 @@ Object.defineProperties(Cesium3DTile.prototype, {
     },
   },
 
-  /**
-   * Determines if the tile's content is renderable. <code>false</code> if the
-   * tile has empty content or if it points to an external tileset or implicit content
-   *
-   * @memberof Cesium3DTile.prototype
-   *
-   * @type {boolean}
-   * @readonly
-   *
-   * @private
-   */
-  hasRenderableContent: {
-    get: function () {
-      return (
-        !this.hasEmptyContent &&
-        !this.hasTilesetContent &&
-        !this.hasImplicitContent
-      );
-    },
-  },
-
   /**
    * Determines if the tile has available content to render.  <code>true</code> if the tile's
    * content is ready or if it has expired content that renders while new content loads; otherwise,
@@ -1346,10 +1343,12 @@ async function makeContent(tile, arrayBuffer) {
     preprocessed.contentType === Cesium3DTileContentType.IMPLICIT_SUBTREE_JSON
   ) {
     tile.hasImplicitContent = true;
+    tile.hasRenderableContent = false;
   }
 
   if (preprocessed.contentType === Cesium3DTileContentType.EXTERNAL_TILESET) {
     tile.hasTilesetContent = true;
+    tile.hasRenderableContent = false;
   }
 
   let content;

packages/engine/Source/Scene/Multiple3DTileContent.js

@@ -6,7 +6,6 @@ import Request from "../Core/Request.js";
 import RequestScheduler from "../Core/RequestScheduler.js";
 import RequestState from "../Core/RequestState.js";
 import RequestType from "../Core/RequestType.js";
-import RuntimeError from "../Core/RuntimeError.js";
 import Cesium3DContentGroup from "./Cesium3DContentGroup.js";
 import Cesium3DTileContentType from "./Cesium3DTileContentType.js";
 import Cesium3DTileContentFactory from "./Cesium3DTileContentFactory.js";
@@ -52,6 +51,11 @@ function Multiple3DTileContent(tileset, tile, tilesetResource, contentsJson) {
   // used to help short-circuit computations after a tile was canceled.
   this._cancelCount = 0;
 
+  // The number of contents that turned out to be external tilesets
+  // in createInnerContent. When all contents are external tilesets,
+  // then tile.hasRenderableContent will become `false`
+  this._externalTilesetCount = 0;
+
   const contentCount = this._innerContentHeaders.length;
   this._arrayFetchPromises = new Array(contentCount);
   this._requests = new Array(contentCount);
@@ -505,6 +509,16 @@ async function createInnerContents(multipleContents) {
   const contents = await Promise.all(promises);
   multipleContents._contentsCreated = true;
   multipleContents._contents = contents.filter(defined);
+
+  // If each content is an external tileset, then the tile
+  // itself does not have any renderable content
+  if (
+    multipleContents._externalTilesetCount === multipleContents._contents.length
+  ) {
+    const tile = multipleContents._tile;
+    tile.hasRenderableContent = false;
+  }
+
   return contents;
 }
 
@@ -518,21 +532,20 @@ async function createInnerContent(multipleContents, arrayBuffer, index) {
   try {
     const preprocessed = preprocess3DTileContent(arrayBuffer);
 
+    const tileset = multipleContents._tileset;
+    const resource = multipleContents._innerContentResources[index];
+    const tile = multipleContents._tile;
+
     if (preprocessed.contentType === Cesium3DTileContentType.EXTERNAL_TILESET) {
-      throw new RuntimeError(
-        "External tilesets are disallowed inside multiple contents",
-      );
+      multipleContents._externalTilesetCount++;
+      tile.hasTilesetContent = true;
     }
 
     multipleContents._disableSkipLevelOfDetail =
       multipleContents._disableSkipLevelOfDetail ||
       preprocessed.contentType === Cesium3DTileContentType.GEOMETRY ||
       preprocessed.contentType === Cesium3DTileContentType.VECTOR;
 
-    const tileset = multipleContents._tileset;
-    const resource = multipleContents._innerContentResources[index];
-    const tile = multipleContents._tile;
-
     let content;
     const contentFactory = Cesium3DTileContentFactory[preprocessed.contentType];
     if (defined(preprocessed.binaryPayload)) {

packages/engine/Specs/Scene/Cesium3DTilesetHeatmapSpec.js

@@ -102,7 +102,7 @@ describe("Scene/Cesium3DTilesetHeatmap", function () {
       undefined,
     );
     tile._contentState = Cesium3DTileContentState.READY;
-    tile.hasEmptyContent = false;
+    tile.hasRenderableContent = true; // Mock the tile having content
     const frameState = scene.frameState;
     tile._selectedFrame = frameState.frameNumber;
     const originalColor = tile._debugColor;