gltf spec updates

packages/engine/Source/Scene/Cesium3DTileContentFactory.js

@@ -93,28 +93,14 @@ const Cesium3DTileContentFactory = {
     const dataView = new DataView(arrayBuffer, byteOffset);
     const byteLength = dataView.getUint32(8, true);
     const glb = new Uint8Array(arrayBuffer, byteOffset, byteLength);
-    let hasGaussianSplatExtension = false;
-    if (tileset.isGltfExtensionRequired instanceof Function) {
-      hasGaussianSplatExtension = tileset.isGltfExtensionRequired(
-        "KHR_spz_gaussian_splats_compression",
-      );
-    }
-    if (hasGaussianSplatExtension) {
+    if (GaussianSplat3DTileContent.tilesetHasGaussianSplattingExt(tileset)) {
       return GaussianSplat3DTileContent.fromGltf(tileset, tile, resource, glb);
     }
 
     return Model3DTileContent.fromGltf(tileset, tile, resource, glb);
   },
   gltf: function (tileset, tile, resource, json) {
-    const forceGaussianSplats =
-      tileset.debugTreatTilesetAsGaussianSplats ?? false;
-    let hasGaussianSplatExtension = false;
-    if (tileset.isGltfExtensionRequired instanceof Function) {
-      hasGaussianSplatExtension = tileset.isGltfExtensionRequired(
-        "KHR_spz_gaussian_splats_compression",
-      );
-    }
-    if (forceGaussianSplats || hasGaussianSplatExtension) {
+    if (GaussianSplat3DTileContent.tilesetHasGaussianSplattingExt(tileset)) {
       return GaussianSplat3DTileContent.fromGltf(tileset, tile, resource, json);
     }
 

packages/engine/Source/Scene/GaussianSplat3DTileContent.js

@@ -7,6 +7,7 @@ import GaussianSplatPrimitive from "./GaussianSplatPrimitive.js";
 import destroyObject from "../Core/destroyObject.js";
 import ModelUtility from "./Model/ModelUtility.js";
 import VertexAttributeSemantic from "./VertexAttributeSemantic.js";
+import deprecationWarning from "../Core/deprecationWarning.js";
 
 /**
  * Represents the contents of a glTF or glb using the {@link https://github.com/CesiumGS/glTF/tree/draft-spz-splat-compression/extensions/2.0/Khronos/KHR_spz_gaussian_splats_compression|KHR_spz_gaussian_splats_compression} extension.
@@ -325,6 +326,34 @@ Object.defineProperties(GaussianSplat3DTileContent.prototype, {
   },
 });
 
+GaussianSplat3DTileContent.tilesetHasGaussianSplattingExt = function (tileset) {
+  let hasGaussianSplatExtension = false;
+  let hasLegacyGaussianSplatExtension = false;
+  if (tileset.isGltfExtensionRequired instanceof Function) {
+    hasGaussianSplatExtension =
+      tileset.isGltfExtensionRequired("KHR_gaussian_splatting") &&
+      tileset.isGltfExtensionRequired(
+        "KHR_gaussian_splatting_compression_spz_2",
+      );
+
+    hasLegacyGaussianSplatExtension = tileset.isGltfExtensionRequired(
+      "KHR_spz_gaussian_splats_compression",
+    );
+  }
+
+  if (hasLegacyGaussianSplatExtension) {
+    deprecationWarning(
+      "KHR_spz_gaussian_splats_compression",
+      "Support for the original KHR_spz_gaussian_splats_compression extension has been deprecated in favor " +
+        "of the up to date KHR_gaussian_splatting and KHR_gaussian_splatting_compression_spz_2 extensions and will be " +
+        "removed in CesiumJS 1.134.\n\nPlease retile your tileset with the KHR_gaussian_splatting and " +
+        "KHR_gaussian_splatting_compression_spz_2 extensions.",
+    );
+  }
+
+  return hasGaussianSplatExtension || hasLegacyGaussianSplatExtension;
+};
+
 /**
  * Determine Spherical Harmonics degree and coefficient count from attributes
  * @param {Array} attributes - The list of attributes.

packages/engine/Source/Scene/GltfLoader.js

@@ -2020,8 +2020,16 @@ function loadPrimitive(loader, gltfPrimitive, hasInstances, frameState) {
     );
   }
 
-  const spzExtension = extensions.KHR_spz_gaussian_splats_compression;
-  if (defined(spzExtension)) {
+  //support the latest glTF spec and the legacy extension
+  const gsExtension = extensions.KHR_spz_gaussian_splatting;
+  const spzExtension =
+    gsExtension?.extensions.KHR_gaussian_splatting_compression_2;
+  const legacySpzExtension = extensions.KHR_spz_gaussian_splats_compression;
+
+  if (
+    defined(gsExtension) &&
+    (defined(spzExtension) || defined(legacySpzExtension))
+  ) {
     needsPostProcessing = true;
     primitivePlan.needsGaussianSplats = true;
   }
@@ -2058,7 +2066,7 @@ function loadPrimitive(loader, gltfPrimitive, hasInstances, frameState) {
         semanticInfo,
         gltfPrimitive,
         draco,
-        spzExtension,
+        spzExtension || legacySpzExtension,
         hasInstances,
         needsPostProcessing,
         frameState,

packages/engine/Source/Scene/GltfVertexBufferLoader.js

@@ -306,8 +306,15 @@ async function loadFromSpz(vertexBufferLoader) {
   }
 }
 
+function getShPrefix(attribute) {
+  const prefix = attribute.startsWith("KHR_gaussian_splatting:")
+    ? "KHR_gaussian_splatting:"
+    : "_";
+  return `${prefix}SH_DEGREE_`;
+}
+
 function extractSHDegreeAndCoef(attribute) {
-  const prefix = "_SH_DEGREE_";
+  const prefix = getShPrefix(attribute);
   const separator = "_COEF_";
 
   const lStart = prefix.length;
@@ -327,9 +334,15 @@ function processSpz(vertexBufferLoader) {
 
   if (vertexBufferLoader._attributeSemantic === "POSITION") {
     vertexBufferLoader._typedArray = gcloudData.positions;
-  } else if (vertexBufferLoader._attributeSemantic === "_SCALE") {
+  } else if (
+    vertexBufferLoader._attributeSemantic === "_SCALE" ||
+    vertexBufferLoader._attributeSemantic === "KHR_gaussian_splatting:SCALE"
+  ) {
     vertexBufferLoader._typedArray = gcloudData.scales;
-  } else if (vertexBufferLoader._attributeSemantic === "_ROTATION") {
+  } else if (
+    vertexBufferLoader._attributeSemantic === "_ROTATION" ||
+    vertexBufferLoader._attributeSemantic === "KHR_gaussian_splatting:ROTATION"
+  ) {
     vertexBufferLoader._typedArray = gcloudData.rotations;
   } else if (vertexBufferLoader._attributeSemantic === "COLOR_0") {
     const colors = gcloudData.colors;
@@ -357,7 +370,7 @@ function processSpz(vertexBufferLoader) {
         255.0,
       );
     }
-  } else if (vertexBufferLoader._attributeSemantic.startsWith("_SH_DEGREE_")) {
+  } else if (vertexBufferLoader._attributeSemantic.includes("SH_DEGREE_")) {
     const { l, n } = extractSHDegreeAndCoef(
       vertexBufferLoader._attributeSemantic,
     );

packages/engine/Source/Scene/PrimitiveLoadPlan.js

@@ -160,7 +160,7 @@ function PrimitiveLoadPlan(primitive) {
 
   /**
    * Set this true to indicate that the primitive has the
-   * KHR_gaussian_splatting extension and needs to be post-processed
+   * KHR_gaussian_splatting and KHR_gaussian_splatting_compression_spz_2 extension and needs to be post-processed
    *
    * @type {boolean}
    * @private

packages/engine/Source/Scene/VertexAttributeSemantic.js

@@ -79,14 +79,14 @@ const VertexAttributeSemantic = {
    * @type {string}
    * @constant
    */
-  SCALE: "_SCALE",
+  SCALE: "KHR_gaussian_splatting:SCALE",
   /**
    * Gaussian Splat Rotation
    *
    * @type {string}
    * @constant
    */
-  ROTATION: "_ROTATION",
+  ROTATION: "KHR_gaussian_splatting:ROTATION",
 };
 
 function semanticToVariableName(semantic) {
@@ -193,8 +193,10 @@ VertexAttributeSemantic.fromGltfSemantic = function (gltfSemantic) {
     case "_FEATURE_ID":
       return VertexAttributeSemantic.FEATURE_ID;
     case "_SCALE":
+    case "KHR_gaussian_splatting:SCALE":
       return VertexAttributeSemantic.SCALE;
     case "_ROTATION":
+    case "KHR_gaussian_splatting:ROTATION":
       return VertexAttributeSemantic.ROTATION;
   }
 
@@ -284,7 +286,7 @@ VertexAttributeSemantic.getGlslType = function (semantic) {
  * @param {VertexAttributeSemantic} semantic The semantic.
  * @param {number} [setIndex] The set index.
  *
- * @returns {string} The variable name.
+ * @returns {string} The varia_SCALEble name.
  *
  * @private
  */