alexchuber · alexchuber · Dec 9, 2024
diff --git a/packages/dev/core/src/Meshes/Compression/dracoCodec.ts b/packages/dev/core/src/Meshes/Compression/dracoCodec.ts
@@ -1,8 +1,8 @@
-import type { Nullable } from "core/types";
 import { Tools } from "../../Misc/tools";
 import { AutoReleaseWorkerPool } from "../../Misc/workerPool";
 import type { IDisposable } from "../../scene";
 import { initializeWebWorker } from "./dracoCompressionWorker";
+import { Logger } from "core/Misc";
 
 /**
  * Configuration for using a Draco codec.
@@ -68,39 +68,9 @@ export abstract class DracoCodec<M> implements IDisposable {
     protected _modulePromise?: Promise<{ module: M }>;
 
     /**
-     * The configuration for the Draco codec.
-     * Subclasses should override this value with a valid configuration.
+     * The default configuration for the codec.
      */
-    public static Config: IDracoCodecConfiguration;
-
-    /**
-     * Returns true if the codec's `Configuration` is available.
-     */
-    public static get Available(): boolean {
-        return !!((this.Config.wasmUrl && this.Config.wasmBinaryUrl && typeof WebAssembly === "object") || this.Config.fallbackUrl);
-    }
-
-    /**
-     * The default draco compression object
-     * Subclasses should override this value using the narrowed type of the subclass,
-     * and define a public `get Default()` that returns the narrowed instance.
-     */
-    protected static _Default: Nullable<DracoCodec<unknown>>;
-
-    /**
-     * Reset the default draco compression object to null and disposing the removed default instance.
-     * Note that if the workerPool is a member of the static Configuration object it is recommended not to run dispose,
-     * unless the static worker pool is no longer needed.
-     * @param skipDispose set to true to not dispose the removed default instance
-     */
-    public static ResetDefault(skipDispose?: boolean): void {
-        if (this._Default) {
-            if (!skipDispose) {
-                this._Default.dispose();
-            }
-            this._Default = null;
-        }
-    }
+    protected abstract readonly _defaultConfig: IDracoCodecConfiguration;
 
     /**
      * Checks if the default codec JS module is in scope.
@@ -118,11 +88,21 @@ export abstract class DracoCodec<M> implements IDisposable {
     protected abstract _getWorkerContent(): string;
 
     /**
-     * Constructor
-     * @param _config The configuration for the DracoCodec instance.
+     * Loads the codec module and worker pool if needed.
+     * @param _config An optional configuration for this DracoDecoder. Defaults to the following:
+     * - `numWorkers`: 50% of the available logical processors, capped to 4. If no logical processors are available, defaults to 1.
+     * - `wasmUrl`: `"https://cdn.babylonjs.com/draco_wasm_wrapper_gltf.js"` (decoder)
+     * - `wasmBinaryUrl`: `"https://cdn.babylonjs.com/draco_decoder_gltf.wasm"` (decoder)
+     * - `fallbackUrl`: `"https://cdn.babylonjs.com/draco_decoder_gltf.js"` (decoder)
+     * @returns A promise that resolves when the decoder is ready (module loaded and/or worker pool initialized)
      */
-    constructor(_config: IDracoCodecConfiguration) {
-        const config = { numWorkers: _GetDefaultNumWorkers(), ..._config };
+    public async initialize(_config?: IDracoCodecConfiguration): Promise<void> {
+        if (this._workerPoolPromise || this._modulePromise) {
+            Logger.Warn("Draco codec is already initialized. If a configuration change is needed, call dispose() before re-initializing.");
+            return;
+        }
+
+        const config = { numWorkers: _GetDefaultNumWorkers(), ...this._defaultConfig, ..._config };
         // check if the decoder binary and worker pool was injected
         // Note - it is expected that the developer checked if WebWorker, WebAssembly and the URL object are available
         if (config.workerPool) {
@@ -148,7 +128,7 @@ export abstract class DracoCodec<M> implements IDisposable {
                       url: urlNeeded ? Tools.GetBabylonScriptURL(config.fallbackUrl!) : "",
                       wasmBinaryPromise: Promise.resolve(undefined),
                   };
-        // If using workers, initialize a worker pool with either the wasm or url?
+        // If using workers, initialize a worker pool with either the wasm or url
         if (useWorkers) {
             this._workerPoolPromise = codecInfo.wasmBinaryPromise.then((wasmBinary) => {
                 const workerContent = this._getWorkerContent();
@@ -159,6 +139,8 @@ export abstract class DracoCodec<M> implements IDisposable {
                     return initializeWebWorker(worker, wasmBinary, codecInfo.url);
                 });
             });
+            await this._workerPoolPromise;
+            return;
         } else {
             this._modulePromise = codecInfo.wasmBinaryPromise.then(async (wasmBinary) => {
                 if (this._isModuleAvailable()) {
@@ -171,20 +153,6 @@ export abstract class DracoCodec<M> implements IDisposable {
                 }
                 return this._createModuleAsync(wasmBinary as ArrayBuffer, config.jsModule);
             });
-        }
-    }
-
-    /**
-     * Returns a promise that resolves when ready. Call this manually to ensure draco compression is ready before use.
-     * @returns a promise that resolves when ready
-     */
-    public async whenReadyAsync(): Promise<void> {
-        if (this._workerPoolPromise) {
-            await this._workerPoolPromise;
-            return;
-        }
-
-        if (this._modulePromise) {
             await this._modulePromise;
             return;
         }

diff --git a/packages/dev/core/src/Meshes/Compression/dracoCompression.ts b/packages/dev/core/src/Meshes/Compression/dracoCompression.ts
@@ -1,8 +1,9 @@
 import { _GetDefaultNumWorkers } from "./dracoCodec";
 import type { IDracoCodecConfiguration } from "./dracoCodec";
-import { DracoDecoder } from "./dracoDecoder";
+import { DefaultDecoderConfig, DracoDecoderClass } from "./dracoDecoder";
 import { VertexBuffer } from "../buffer";
 import { VertexData } from "../mesh.vertexData";
+import type { Nullable } from "core/types";
 
 /**
  * Configuration for Draco compression
@@ -54,36 +55,84 @@ export interface IDracoCompressionOptions extends Pick<IDracoCodecConfiguration,
  *
  * @see https://playground.babylonjs.com/#DMZIBD#0
  */
-export class DracoCompression extends DracoDecoder {
+export class DracoCompression extends DracoDecoderClass {
     /**
      * The configuration. Defaults to the following urls:
      * - wasmUrl: "https://cdn.babylonjs.com/draco_wasm_wrapper_gltf.js"
      * - wasmBinaryUrl: "https://cdn.babylonjs.com/draco_decoder_gltf.wasm"
      * - fallbackUrl: "https://cdn.babylonjs.com/draco_decoder_gltf.js"
      */
     public static Configuration: IDracoCompressionConfiguration = {
-        decoder: DracoDecoder.Config, // TODO: Remove this reference or update the JSDoc with warning.
+        decoder: { ...DefaultDecoderConfig },
     };
 
     /**
      * Returns true if the decoder configuration is available.
      */
     public static get DecoderAvailable(): boolean {
-        return DracoDecoder.Available; // TODO: Remove this reference or update the JSDoc with warning.
+        const decoder = DracoCompression.Configuration.decoder;
+        return !!((decoder.wasmUrl && decoder.wasmBinaryUrl && typeof WebAssembly === "object") || decoder.fallbackUrl);
     }
 
     /**
      * Default number of workers to create when creating the draco compression object.
      */
     public static DefaultNumWorkers = _GetDefaultNumWorkers();
 
+    protected static _Default: Nullable<DracoCompression>;
+
+    /**
+     * Default instance for the draco compression object.
+     */
+    public static get Default(): DracoCompression {
+        DracoCompression._Default ??= new DracoCompression();
+        return DracoCompression._Default;
+    }
+
+    /**
+     * Reset the default draco compression object to null and disposing the removed default instance.
+     * Note that if the workerPool is a member of the static Configuration object it is recommended not to run dispose,
+     * unless the static worker pool is no longer needed.
+     * @param skipDispose set to true to not dispose the removed default instance
+     */
+    public static ResetDefault(skipDispose?: boolean): void {
+        if (DracoCompression._Default) {
+            if (!skipDispose) {
+                DracoCompression._Default.dispose();
+            }
+            DracoCompression._Default = null;
+        }
+    }
+
     /**
      * Constructor
      * @param numWorkersOrConfig The number of workers for async operations or a config object. Specify `0` to disable web workers and run synchronously in the current context.
      */
     constructor(numWorkersOrConfig: number | IDracoCompressionOptions = DracoCompression.DefaultNumWorkers) {
-        const config = typeof numWorkersOrConfig === "number" ? { ...DracoDecoder.Config, numWorkers: numWorkersOrConfig } : { ...DracoDecoder.Config, ...numWorkersOrConfig };
-        super(config);
+        super();
+        // Derive config this way to maintain backwards compatibility with "numWorkers"
+        const mergedConfig = {
+            ...DracoCompression.Configuration.decoder,
+            ...(typeof numWorkersOrConfig === "number" ? { numWorkers: numWorkersOrConfig } : numWorkersOrConfig),
+        };
+        // Explicitly initialize here for backwards compatibility
+        this.initialize(mergedConfig);
+    }
+
+    /**
+     * Returns a promise that resolves when ready. Call this manually to ensure draco compression is ready before use.
+     * @returns a promise that resolves when ready
+     */
+    public async whenReadyAsync(): Promise<void> {
+        if (this._workerPoolPromise) {
+            await this._workerPoolPromise;
+            return;
+        }
+
+        if (this._modulePromise) {
+            await this._modulePromise;
+            return;
+        }
     }
 
     /**

diff --git a/packages/dev/core/src/Meshes/Compression/dracoDecoder.ts b/packages/dev/core/src/Meshes/Compression/dracoDecoder.ts
@@ -20,55 +20,20 @@ interface MeshData {
     totalVertices: number;
 }
 
+/** @internal Used for `DracoCompression` */
+export const DefaultDecoderConfig: IDracoCodecConfiguration = {
+    wasmUrl: `${Tools._DefaultCdnUrl}/draco_wasm_wrapper_gltf.js`,
+    wasmBinaryUrl: `${Tools._DefaultCdnUrl}/draco_decoder_gltf.wasm`,
+    fallbackUrl: `${Tools._DefaultCdnUrl}/draco_decoder_gltf.js`,
+};
+
 /**
- * @experimental This class is an experimental version of `DracoCompression` and is subject to change.
- *
- * Draco compression (https://google.github.io/draco/)
- *
  * This class wraps the Draco decoder module.
- *
- * By default, the configuration points to a copy of the Draco decoder files for glTF from the Babylon.js preview cdn https://preview.babylonjs.com/draco_wasm_wrapper_gltf.js.
- *
- * To update the configuration, use the following code:
- * ```javascript
- *     DracoDecoder.Config = {
- *          wasmUrl: "<url to the WebAssembly library>",
- *          wasmBinaryUrl: "<url to the WebAssembly binary>",
- *          fallbackUrl: "<url to the fallback JavaScript library>",
- *     };
- * ```
- *
- * Draco has two versions, one for WebAssembly and one for JavaScript. The decoder configuration can be set to only support WebAssembly or only support the JavaScript version.
- * Decoding will automatically fallback to the JavaScript version if WebAssembly version is not configured or if WebAssembly is not supported by the browser.
- * Use `DracoDecoder.Available` to determine if the decoder configuration is available for the current context.
- *
- * To decode Draco compressed data, get the default DracoDecoder object and call decodeMeshToGeometryAsync:
- * ```javascript
- *     var geometry = await DracoDecoder.Default.decodeMeshToGeometryAsync(data);
- * ```
+ * It should not be constructed directly. Use `DracoDecoder` instead.
+ * @internal
  */
-export class DracoDecoder extends DracoCodec<DecoderModule> {
-    protected static override _Default: Nullable<DracoDecoder> = null;
-    /**
-     * Default instance for the DracoDecoder.
-     */
-    public static get Default(): DracoDecoder {
-        DracoDecoder._Default ??= new DracoDecoder();
-        return DracoDecoder._Default;
-    }
-
-    /**
-     * Configuration for the DracoDecoder. Defaults to the following:
-     * - numWorkers: 50% of the available logical processors, capped to 4. If no logical processors are available, defaults to 1.
-     * - wasmUrl: `"https://cdn.babylonjs.com/draco_wasm_wrapper_gltf.js"`
-     * - wasmBinaryUrl: `"https://cdn.babylonjs.com/draco_decoder_gltf.wasm"`
-     * - fallbackUrl: `"https://cdn.babylonjs.com/draco_decoder_gltf.js"`
-     */
-    public static override Config: IDracoCodecConfiguration = {
-        wasmUrl: `${Tools._DefaultCdnUrl}/draco_wasm_wrapper_gltf.js`,
-        wasmBinaryUrl: `${Tools._DefaultCdnUrl}/draco_decoder_gltf.wasm`,
-        fallbackUrl: `${Tools._DefaultCdnUrl}/draco_decoder_gltf.js`,
-    };
+export class DracoDecoderClass extends DracoCodec<DecoderModule> {
+    protected override readonly _defaultConfig: IDracoCodecConfiguration = DefaultDecoderConfig;
 
     protected override _isModuleAvailable(): boolean {
         return typeof DracoDecoderModule !== "undefined";
@@ -83,15 +48,6 @@ export class DracoDecoder extends DracoCodec<DecoderModule> {
         return `${decodeMesh}(${workerFunction})()`;
     }
 
-    /**
-     * Creates a new Draco decoder.
-     * @param config Optional override of the configuration for the DracoDecoder. If not provided, defaults to `DracoDecoder.Config`.
-     */
-    constructor(config?: IDracoCodecConfiguration) {
-        // Order of final config will be config > DracoDecoder.Config.
-        super({ ...DracoDecoder.Config, ...(config ?? {}) });
-    }
-
     /**
      * Decode Draco compressed mesh data to mesh data.
      * @param data The ArrayBuffer or ArrayBufferView for the Draco compression data
@@ -200,7 +156,8 @@ export class DracoDecoder extends DracoCodec<DecoderModule> {
             });
         }
 
-        throw new Error("Draco decoder module is not available");
+        throw new Error("Draco decoder module is not available. Have you called initialize()?");
+        // NOTE: Alternatively, we could initialize the module here if the user forgot.
     }
 
     /**
@@ -279,3 +236,36 @@ export class DracoDecoder extends DracoCodec<DecoderModule> {
         return geometry;
     }
 }
+
+/**
+ * @experimental
+ * Draco compression (https://google.github.io/draco/)
+ *
+ * DracoDecoder is a singleton for decoding Draco-compressed meshes.
+ * It is automatically constructed when the module is imported.
+ *
+ * To decode Draco compressed data, see the following example:
+ * ```javascript
+ *     DracoDecoder.initialize(//Optional configuration//);
+ *     var geometry = await DracoDecoder.decodeMeshToGeometryAsync(data);
+       // Perform any additional decoding here
+ *     DracoDecoder.dispose();
+ * ```
+ * 
+ * Before using the DracoDecoder, call initialize to ensure the decoder is ready.
+ * By default, the initialization configuration points to a copy of the Draco decoder files for glTF from the Babylon.js preview cdn https://preview.babylonjs.com/draco_wasm_wrapper_gltf.js.
+ *
+ * This configuration can be customized at initialization using the following code:
+ * ```javascript
+ *     DracoDecoder.initialize({
+ *          wasmUrl: "<url to the WebAssembly library>",
+ *          wasmBinaryUrl: "<url to the WebAssembly binary>",
+ *          fallbackUrl: "<url to the fallback JavaScript library>",
+ *     });
+ * ```
+ *
+ * Draco has two versions, one for WebAssembly and one for JavaScript. The decoder configuration can be set to only support WebAssembly or only support the JavaScript version.
+ * Decoding will automatically fallback to the JavaScript version if WebAssembly version is not configured or if WebAssembly is not supported by the browser.
+ * For custom configurations, it is assumed that the developer has verified its availability in the current context (i.e., the WebAssembly version is correctly configured or a valid fallback exists.)
+ */
+export const DracoDecoder = new DracoDecoderClass();
diff --git a/packages/dev/core/src/Meshes/Compression/index.ts b/packages/dev/core/src/Meshes/Compression/index.ts
@@ -1,3 +1,3 @@
 export * from "./dracoCompression";
 export * from "./meshoptCompression";
-export * from "./dracoDecoder";
+export { DracoDecoder } from "./dracoDecoder";