three.js/examples/jsm/loaders/KTX2Loader.js

/**
 * Loader for KTX 2.0 GPU Texture containers.
 *
 * KTX 2.0 is a container format for various GPU texture formats. The loader
 * supports Basis Universal GPU textures, which can be quickly transcoded to
 * a wide variety of GPU texture compression formats, as well as some
 * uncompressed DataTexture and Data3DTexture formats.
 *
 * References:
 * - KTX: http://github.khronos.org/KTX-Specification/
 * - DFD: https://www.khronos.org/registry/DataFormat/specs/1.3/dataformat.1.3.html#basicdescriptor
 */

import {
	CompressedTexture,
	CompressedArrayTexture,
	Data3DTexture,
	DataTexture,
	FileLoader,
	FloatType,
	HalfFloatType,
	NoColorSpace,
	LinearFilter,
	LinearMipmapLinearFilter,
	Loader,
	RedFormat,
	RGB_ETC1_Format,
	RGB_ETC2_Format,
	RGB_PVRTC_4BPPV1_Format,
	RGB_S3TC_DXT1_Format,
	RGBA_ASTC_4x4_Format,
	RGBA_BPTC_Format,
	RGBA_ETC2_EAC_Format,
	RGBA_PVRTC_4BPPV1_Format,
	RGBA_S3TC_DXT5_Format,
	RGBAFormat,
	RGFormat,
	SRGBColorSpace,
	UnsignedByteType,
} from 'three';
import { WorkerPool } from '../utils/WorkerPool.js';
import {
	read,
	KHR_DF_FLAG_ALPHA_PREMULTIPLIED,
	KHR_DF_TRANSFER_SRGB,
	KHR_SUPERCOMPRESSION_NONE,
	KHR_SUPERCOMPRESSION_ZSTD,
	VK_FORMAT_UNDEFINED,
	VK_FORMAT_R16_SFLOAT,
	VK_FORMAT_R16G16_SFLOAT,
	VK_FORMAT_R16G16B16A16_SFLOAT,
	VK_FORMAT_R32_SFLOAT,
	VK_FORMAT_R32G32_SFLOAT,
	VK_FORMAT_R32G32B32A32_SFLOAT,
	VK_FORMAT_R8_SRGB,
	VK_FORMAT_R8_UNORM,
	VK_FORMAT_R8G8_SRGB,
	VK_FORMAT_R8G8_UNORM,
	VK_FORMAT_R8G8B8A8_SRGB,
	VK_FORMAT_R8G8B8A8_UNORM,
} from '../libs/ktx-parse.module.js';
import { ZSTDDecoder } from '../libs/zstddec.module.js';

const _taskCache = new WeakMap();

let _activeLoaders = 0;

let _zstd;

class KTX2Loader extends Loader {

	constructor( manager ) {

		super( manager );

		this.transcoderPath = '';
		this.transcoderBinary = null;
		this.transcoderPending = null;

		this.workerPool = new WorkerPool();
		this.workerSourceURL = '';
		this.workerConfig = null;

		if ( typeof MSC_TRANSCODER !== 'undefined' ) {

			console.warn(

				'THREE.KTX2Loader: Please update to latest "basis_transcoder".'
				+ ' "msc_basis_transcoder" is no longer supported in three.js r125+.'

			);

		}

	}

	setTranscoderPath( path ) {

		this.transcoderPath = path;

		return this;

	}

	setWorkerLimit( num ) {

		this.workerPool.setWorkerLimit( num );

		return this;

	}

	detectSupport( renderer ) {

		if ( renderer.isWebGPURenderer === true ) {

			this.workerConfig = {
				astcSupported: renderer.hasFeature( 'texture-compression-astc' ),
				etc1Supported: false,
				etc2Supported: renderer.hasFeature( 'texture-compression-etc2' ),
				dxtSupported: renderer.hasFeature( 'texture-compression-bc' ),
				bptcSupported: false,
				pvrtcSupported: false
			};

		} else {

			this.workerConfig = {
				astcSupported: renderer.extensions.has( 'WEBGL_compressed_texture_astc' ),
				etc1Supported: renderer.extensions.has( 'WEBGL_compressed_texture_etc1' ),
				etc2Supported: renderer.extensions.has( 'WEBGL_compressed_texture_etc' ),
				dxtSupported: renderer.extensions.has( 'WEBGL_compressed_texture_s3tc' ),
				bptcSupported: renderer.extensions.has( 'EXT_texture_compression_bptc' ),
				pvrtcSupported: renderer.extensions.has( 'WEBGL_compressed_texture_pvrtc' )
					|| renderer.extensions.has( 'WEBKIT_WEBGL_compressed_texture_pvrtc' )
			};

			if ( renderer.capabilities.isWebGL2 ) {

				// https://github.com/mrdoob/three.js/pull/22928
				this.workerConfig.etc1Supported = false;

			}

		}

		return this;

	}

	init() {

		if ( ! this.transcoderPending ) {

			// Load transcoder wrapper.
			const jsLoader = new FileLoader( this.manager );
			jsLoader.setPath( this.transcoderPath );
			jsLoader.setWithCredentials( this.withCredentials );
			const jsContent = jsLoader.loadAsync( 'basis_transcoder.js' );

			// Load transcoder WASM binary.
			const binaryLoader = new FileLoader( this.manager );
			binaryLoader.setPath( this.transcoderPath );
			binaryLoader.setResponseType( 'arraybuffer' );
			binaryLoader.setWithCredentials( this.withCredentials );
			const binaryContent = binaryLoader.loadAsync( 'basis_transcoder.wasm' );

			this.transcoderPending = Promise.all( [ jsContent, binaryContent ] )
				.then( ( [ jsContent, binaryContent ] ) => {

					const fn = KTX2Loader.BasisWorker.toString();

					const body = [
						'/* constants */',
						'let _EngineFormat = ' + JSON.stringify( KTX2Loader.EngineFormat ),
						'let _TranscoderFormat = ' + JSON.stringify( KTX2Loader.TranscoderFormat ),
						'let _BasisFormat = ' + JSON.stringify( KTX2Loader.BasisFormat ),
						'/* basis_transcoder.js */',
						jsContent,
						'/* worker */',
						fn.substring( fn.indexOf( '{' ) + 1, fn.lastIndexOf( '}' ) )
					].join( '\n' );

					this.workerSourceURL = URL.createObjectURL( new Blob( [ body ] ) );
					this.transcoderBinary = binaryContent;

					this.workerPool.setWorkerCreator( () => {

						const worker = new Worker( this.workerSourceURL );
						const transcoderBinary = this.transcoderBinary.slice( 0 );

						worker.postMessage( { type: 'init', config: this.workerConfig, transcoderBinary }, [ transcoderBinary ] );

						return worker;

					} );

				} );

			if ( _activeLoaders > 0 ) {

				// Each instance loads a transcoder and allocates workers, increasing network and memory cost.

				console.warn(

					'THREE.KTX2Loader: Multiple active KTX2 loaders may cause performance issues.'
					+ ' Use a single KTX2Loader instance, or call .dispose() on old instances.'

				);

			}

			_activeLoaders ++;

		}

		return this.transcoderPending;

	}

	load( url, onLoad, onProgress, onError ) {

		if ( this.workerConfig === null ) {

			throw new Error( 'THREE.KTX2Loader: Missing initialization with `.detectSupport( renderer )`.' );

		}

		const loader = new FileLoader( this.manager );

		loader.setResponseType( 'arraybuffer' );
		loader.setWithCredentials( this.withCredentials );

		loader.load( url, ( buffer ) => {

			// Check for an existing task using this buffer. A transferred buffer cannot be transferred
			// again from this thread.
			if ( _taskCache.has( buffer ) ) {

				const cachedTask = _taskCache.get( buffer );

				return cachedTask.promise.then( onLoad ).catch( onError );

			}

			this._createTexture( buffer )
				.then( ( texture ) => onLoad ? onLoad( texture ) : null )
				.catch( onError );

		}, onProgress, onError );

	}

	_createTextureFrom( transcodeResult, container ) {

		const { faces, width, height, format, type, error, dfdTransferFn, dfdFlags } = transcodeResult;

		if ( type === 'error' ) return Promise.reject( error );

		let texture;

		if ( container.faceCount === 6 ) {

			texture = new CompressedTexture();
			texture.image = faces;
			texture.format = format;
			texture.type = UnsignedByteType;

		} else {

			const mipmaps = faces[ 0 ].mipmaps;

			texture = container.layerCount > 1
				? new CompressedArrayTexture( mipmaps, width, height, container.layerCount, format, UnsignedByteType )
				: new CompressedTexture( mipmaps, width, height, format, UnsignedByteType );

		}

		texture.minFilter = faces[ 0 ].mipmaps.length === 1 ? LinearFilter : LinearMipmapLinearFilter;
		texture.magFilter = LinearFilter;
		texture.generateMipmaps = false;

		texture.needsUpdate = true;
		// TODO: Detect NoColorSpace vs. LinearSRGBColorSpace based on primaries.
		texture.colorSpace = dfdTransferFn === KHR_DF_TRANSFER_SRGB ? SRGBColorSpace : NoColorSpace;
		texture.premultiplyAlpha = !! ( dfdFlags & KHR_DF_FLAG_ALPHA_PREMULTIPLIED );

		return texture;

	}

	/**
	 * @param {ArrayBuffer} buffer
	 * @param {object?} config
	 * @return {Promise<CompressedTexture|CompressedArrayTexture|DataTexture|Data3DTexture>}
	 */
	async _createTexture( buffer, config = {} ) {

		const container = read( new Uint8Array( buffer ) );

		if ( container.vkFormat !== VK_FORMAT_UNDEFINED ) {

			const mipmaps = [];
			const pendings = [];

			for ( let levelIndex = 0; levelIndex < container.levels.length; levelIndex ++ ) {

				pendings.push( createDataTexture( container, levelIndex ).then( function ( dataTexture ) {

					mipmaps[ levelIndex ] = dataTexture;

				} ) );

			}

			await Promise.all( pendings );

			const texture = mipmaps[ 0 ];
			texture.mipmaps = mipmaps.map( dt => {
				return {
					data: dt.source.data,
					width: dt.source.data.width,
					height: dt.source.data.height,
					depth: dt.source.data.depth
				};
			} );
			return texture;

		}

		//
		const taskConfig = config;
		const texturePending = this.init().then( () => {

			return this.workerPool.postMessage( { type: 'transcode', buffer, taskConfig: taskConfig }, [ buffer ] );

		} ).then( ( e ) => this._createTextureFrom( e.data, container ) );

		// Cache the task result.
		_taskCache.set( buffer, { promise: texturePending } );

		return texturePending;

	}

	dispose() {

		this.workerPool.dispose();
		if ( this.workerSourceURL ) URL.revokeObjectURL( this.workerSourceURL );

		_activeLoaders --;

		return this;

	}

}


/* CONSTANTS */

KTX2Loader.BasisFormat = {
	ETC1S: 0,
	UASTC_4x4: 1,
};

KTX2Loader.TranscoderFormat = {
	ETC1: 0,
	ETC2: 1,
	BC1: 2,
	BC3: 3,
	BC4: 4,
	BC5: 5,
	BC7_M6_OPAQUE_ONLY: 6,
	BC7_M5: 7,
	PVRTC1_4_RGB: 8,
	PVRTC1_4_RGBA: 9,
	ASTC_4x4: 10,
	ATC_RGB: 11,
	ATC_RGBA_INTERPOLATED_ALPHA: 12,
	RGBA32: 13,
	RGB565: 14,
	BGR565: 15,
	RGBA4444: 16,
};

KTX2Loader.EngineFormat = {
	RGBAFormat: RGBAFormat,
	RGBA_ASTC_4x4_Format: RGBA_ASTC_4x4_Format,
	RGBA_BPTC_Format: RGBA_BPTC_Format,
	RGBA_ETC2_EAC_Format: RGBA_ETC2_EAC_Format,
	RGBA_PVRTC_4BPPV1_Format: RGBA_PVRTC_4BPPV1_Format,
	RGBA_S3TC_DXT5_Format: RGBA_S3TC_DXT5_Format,
	RGB_ETC1_Format: RGB_ETC1_Format,
	RGB_ETC2_Format: RGB_ETC2_Format,
	RGB_PVRTC_4BPPV1_Format: RGB_PVRTC_4BPPV1_Format,
	RGB_S3TC_DXT1_Format: RGB_S3TC_DXT1_Format,
};


/* WEB WORKER */

KTX2Loader.BasisWorker = function () {

	let config;
	let transcoderPending;
	let BasisModule;

	const EngineFormat = _EngineFormat; // eslint-disable-line no-undef
	const TranscoderFormat = _TranscoderFormat; // eslint-disable-line no-undef
	const BasisFormat = _BasisFormat; // eslint-disable-line no-undef

	self.addEventListener( 'message', function ( e ) {

		const message = e.data;

		switch ( message.type ) {

			case 'init':
				config = message.config;
				init( message.transcoderBinary );
				break;

			case 'transcode':
				transcoderPending.then( () => {

					try {

						const { faces, buffers, width, height, hasAlpha, format, dfdTransferFn, dfdFlags } = transcode( message.buffer );

						self.postMessage( { type: 'transcode', id: message.id, faces, width, height, hasAlpha, format, dfdTransferFn, dfdFlags }, buffers );

					} catch ( error ) {

						console.error( error );

						self.postMessage( { type: 'error', id: message.id, error: error.message } );

					}

				} );
				break;

		}

	} );

	function init( wasmBinary ) {

		transcoderPending = new Promise( ( resolve ) => {

			BasisModule = { wasmBinary, onRuntimeInitialized: resolve };
			BASIS( BasisModule ); // eslint-disable-line no-undef

		} ).then( () => {

			BasisModule.initializeBasis();

			if ( BasisModule.KTX2File === undefined ) {

				console.warn( 'THREE.KTX2Loader: Please update Basis Universal transcoder.' );

			}

		} );

	}

	function transcode( buffer ) {

		const ktx2File = new BasisModule.KTX2File( new Uint8Array( buffer ) );

		function cleanup() {

			ktx2File.close();
			ktx2File.delete();

		}

		if ( ! ktx2File.isValid() ) {

			cleanup();
			throw new Error( 'THREE.KTX2Loader:	Invalid or unsupported .ktx2 file' );

		}

		const basisFormat = ktx2File.isUASTC() ? BasisFormat.UASTC_4x4 : BasisFormat.ETC1S;
		const width = ktx2File.getWidth();
		const height = ktx2File.getHeight();
		const layerCount = ktx2File.getLayers() || 1;
		const levelCount = ktx2File.getLevels();
		const faceCount = ktx2File.getFaces();
		const hasAlpha = ktx2File.getHasAlpha();
		const dfdTransferFn = ktx2File.getDFDTransferFunc();
		const dfdFlags = ktx2File.getDFDFlags();

		const { transcoderFormat, engineFormat } = getTranscoderFormat( basisFormat, width, height, hasAlpha );

		if ( ! width || ! height || ! levelCount ) {

			cleanup();
			throw new Error( 'THREE.KTX2Loader:	Invalid texture' );

		}

		if ( ! ktx2File.startTranscoding() ) {

			cleanup();
			throw new Error( 'THREE.KTX2Loader: .startTranscoding failed' );

		}

		const faces = [];
		const buffers = [];

		for ( let face = 0; face < faceCount; face ++ ) {

			const mipmaps = [];

			for ( let mip = 0; mip < levelCount; mip ++ ) {

				const layerMips = [];

				let mipWidth, mipHeight;

				for ( let layer = 0; layer < layerCount; layer ++ ) {

					const levelInfo = ktx2File.getImageLevelInfo( mip, layer, face );
					mipWidth = levelInfo.origWidth < 4 ? levelInfo.origWidth : levelInfo.width;
					mipHeight = levelInfo.origHeight < 4 ? levelInfo.origHeight : levelInfo.height;
					const dst = new Uint8Array( ktx2File.getImageTranscodedSizeInBytes( mip, layer, 0, transcoderFormat ) );
					const status = ktx2File.transcodeImage( dst, mip, layer, face, transcoderFormat, 0, - 1, - 1 );

					if ( ! status ) {

						cleanup();
						throw new Error( 'THREE.KTX2Loader: .transcodeImage failed.' );

					}

					layerMips.push( dst );

				}

				const mipData = concat( layerMips );

				mipmaps.push( { data: mipData, width: mipWidth, height: mipHeight } );
				buffers.push( mipData.buffer );

			}

			faces.push( { mipmaps, width, height, format: engineFormat } );

		}

		cleanup();

		return { faces, buffers, width, height, hasAlpha, format: engineFormat, dfdTransferFn, dfdFlags };

	}

	//

	// Optimal choice of a transcoder target format depends on the Basis format (ETC1S or UASTC),
	// device capabilities, and texture dimensions. The list below ranks the formats separately
	// for ETC1S and UASTC.
	//
	// In some cases, transcoding UASTC to RGBA32 might be preferred for higher quality (at
	// significant memory cost) compared to ETC1/2, BC1/3, and PVRTC. The transcoder currently
	// chooses RGBA32 only as a last resort and does not expose that option to the caller.
	const FORMAT_OPTIONS = [
		{
			if: 'astcSupported',
			basisFormat: [ BasisFormat.UASTC_4x4 ],
			transcoderFormat: [ TranscoderFormat.ASTC_4x4, TranscoderFormat.ASTC_4x4 ],
			engineFormat: [ EngineFormat.RGBA_ASTC_4x4_Format, EngineFormat.RGBA_ASTC_4x4_Format ],
			priorityETC1S: Infinity,
			priorityUASTC: 1,
			needsPowerOfTwo: false,
		},
		{
			if: 'bptcSupported',
			basisFormat: [ BasisFormat.ETC1S, BasisFormat.UASTC_4x4 ],
			transcoderFormat: [ TranscoderFormat.BC7_M5, TranscoderFormat.BC7_M5 ],
			engineFormat: [ EngineFormat.RGBA_BPTC_Format, EngineFormat.RGBA_BPTC_Format ],
			priorityETC1S: 3,
			priorityUASTC: 2,
			needsPowerOfTwo: false,
		},
		{
			if: 'dxtSupported',
			basisFormat: [ BasisFormat.ETC1S, BasisFormat.UASTC_4x4 ],
			transcoderFormat: [ TranscoderFormat.BC1, TranscoderFormat.BC3 ],
			engineFormat: [ EngineFormat.RGB_S3TC_DXT1_Format, EngineFormat.RGBA_S3TC_DXT5_Format ],
			priorityETC1S: 4,
			priorityUASTC: 5,
			needsPowerOfTwo: false,
		},
		{
			if: 'etc2Supported',
			basisFormat: [ BasisFormat.ETC1S, BasisFormat.UASTC_4x4 ],
			transcoderFormat: [ TranscoderFormat.ETC1, TranscoderFormat.ETC2 ],
			engineFormat: [ EngineFormat.RGB_ETC2_Format, EngineFormat.RGBA_ETC2_EAC_Format ],
			priorityETC1S: 1,
			priorityUASTC: 3,
			needsPowerOfTwo: false,
		},
		{
			if: 'etc1Supported',
			basisFormat: [ BasisFormat.ETC1S, BasisFormat.UASTC_4x4 ],
			transcoderFormat: [ TranscoderFormat.ETC1 ],
			engineFormat: [ EngineFormat.RGB_ETC1_Format ],
			priorityETC1S: 2,
			priorityUASTC: 4,
			needsPowerOfTwo: false,
		},
		{
			if: 'pvrtcSupported',
			basisFormat: [ BasisFormat.ETC1S, BasisFormat.UASTC_4x4 ],
			transcoderFormat: [ TranscoderFormat.PVRTC1_4_RGB, TranscoderFormat.PVRTC1_4_RGBA ],
			engineFormat: [ EngineFormat.RGB_PVRTC_4BPPV1_Format, EngineFormat.RGBA_PVRTC_4BPPV1_Format ],
			priorityETC1S: 5,
			priorityUASTC: 6,
			needsPowerOfTwo: true,
		},
	];

	const ETC1S_OPTIONS = FORMAT_OPTIONS.sort( function ( a, b ) {

		return a.priorityETC1S - b.priorityETC1S;

	} );
	const UASTC_OPTIONS = FORMAT_OPTIONS.sort( function ( a, b ) {

		return a.priorityUASTC - b.priorityUASTC;

	} );

	function getTranscoderFormat( basisFormat, width, height, hasAlpha ) {

		let transcoderFormat;
		let engineFormat;

		const options = basisFormat === BasisFormat.ETC1S ? ETC1S_OPTIONS : UASTC_OPTIONS;

		for ( let i = 0; i < options.length; i ++ ) {

			const opt = options[ i ];

			if ( ! config[ opt.if ] ) continue;
			if ( ! opt.basisFormat.includes( basisFormat ) ) continue;
			if ( hasAlpha && opt.transcoderFormat.length < 2 ) continue;
			if ( opt.needsPowerOfTwo && ! ( isPowerOfTwo( width ) && isPowerOfTwo( height ) ) ) continue;

			transcoderFormat = opt.transcoderFormat[ hasAlpha ? 1 : 0 ];
			engineFormat = opt.engineFormat[ hasAlpha ? 1 : 0 ];

			return { transcoderFormat, engineFormat };

		}

		console.warn( 'THREE.KTX2Loader: No suitable compressed texture format found. Decoding to RGBA32.' );

		transcoderFormat = TranscoderFormat.RGBA32;
		engineFormat = EngineFormat.RGBAFormat;

		return { transcoderFormat, engineFormat };

	}

	function isPowerOfTwo( value ) {

		if ( value <= 2 ) return true;

		return ( value & ( value - 1 ) ) === 0 && value !== 0;

	}

	/** Concatenates N byte arrays. */
	function concat( arrays ) {

		if ( arrays.length === 1 ) return arrays[ 0 ];

		let totalByteLength = 0;

		for ( let i = 0; i < arrays.length; i ++ ) {

			const array = arrays[ i ];
			totalByteLength += array.byteLength;

		}

		const result = new Uint8Array( totalByteLength );

		let byteOffset = 0;

		for ( let i = 0; i < arrays.length; i ++ ) {

			const array = arrays[ i ];
			result.set( array, byteOffset );

			byteOffset += array.byteLength;

		}

		return result;

	}

};

//
// DataTexture and Data3DTexture parsing.

const FORMAT_MAP = {

	[ VK_FORMAT_R32G32B32A32_SFLOAT ]: RGBAFormat,
	[ VK_FORMAT_R16G16B16A16_SFLOAT ]: RGBAFormat,
	[ VK_FORMAT_R8G8B8A8_UNORM ]: RGBAFormat,
	[ VK_FORMAT_R8G8B8A8_SRGB ]: RGBAFormat,

	[ VK_FORMAT_R32G32_SFLOAT ]: RGFormat,
	[ VK_FORMAT_R16G16_SFLOAT ]: RGFormat,
	[ VK_FORMAT_R8G8_UNORM ]: RGFormat,
	[ VK_FORMAT_R8G8_SRGB ]: RGFormat,

	[ VK_FORMAT_R32_SFLOAT ]: RedFormat,
	[ VK_FORMAT_R16_SFLOAT ]: RedFormat,
	[ VK_FORMAT_R8_SRGB ]: RedFormat,
	[ VK_FORMAT_R8_UNORM ]: RedFormat,

};

const TYPE_MAP = {

	[ VK_FORMAT_R32G32B32A32_SFLOAT ]: FloatType,
	[ VK_FORMAT_R16G16B16A16_SFLOAT ]: HalfFloatType,
	[ VK_FORMAT_R8G8B8A8_UNORM ]: UnsignedByteType,
	[ VK_FORMAT_R8G8B8A8_SRGB ]: UnsignedByteType,

	[ VK_FORMAT_R32G32_SFLOAT ]: FloatType,
	[ VK_FORMAT_R16G16_SFLOAT ]: HalfFloatType,
	[ VK_FORMAT_R8G8_UNORM ]: UnsignedByteType,
	[ VK_FORMAT_R8G8_SRGB ]: UnsignedByteType,

	[ VK_FORMAT_R32_SFLOAT ]: FloatType,
	[ VK_FORMAT_R16_SFLOAT ]: HalfFloatType,
	[ VK_FORMAT_R8_SRGB ]: UnsignedByteType,
	[ VK_FORMAT_R8_UNORM ]: UnsignedByteType,

};

const COLOR_SPACE_MAP = {

	[ VK_FORMAT_R8G8B8A8_SRGB ]: SRGBColorSpace,
	[ VK_FORMAT_R8G8_SRGB ]: SRGBColorSpace,
	[ VK_FORMAT_R8_SRGB ]: SRGBColorSpace,

};

async function createDataTexture( container, levelIndex = 0 ) {

	const { vkFormat } = container;
	const pixelWidth = Math.max( 1, container.pixelWidth >> levelIndex );
	const pixelHeight = Math.max( 1, container.pixelHeight >> levelIndex );
	const pixelDepth = Math.max( 1, container.pixelDepth >> levelIndex );

	if ( FORMAT_MAP[ vkFormat ] === undefined ) {

		throw new Error( 'THREE.KTX2Loader: Unsupported vkFormat.' );

	}

	const level = container.levels[ levelIndex ];

	let levelData;
	let view;

	if ( container.supercompressionScheme === KHR_SUPERCOMPRESSION_NONE ) {

		levelData = level.levelData;

	} else if ( container.supercompressionScheme === KHR_SUPERCOMPRESSION_ZSTD ) {

		if ( ! _zstd ) {

			_zstd = new Promise( async ( resolve ) => {

				const zstd = new ZSTDDecoder();
				await zstd.init();
				resolve( zstd );

			} );

		}

		levelData = ( await _zstd ).decode( level.levelData, level.uncompressedByteLength );

	} else {

		throw new Error( 'THREE.KTX2Loader: Unsupported supercompressionScheme.' );

	}

	if ( TYPE_MAP[ vkFormat ] === FloatType ) {

		view = new Float32Array(

			levelData.buffer,
			levelData.byteOffset,
			levelData.byteLength / Float32Array.BYTES_PER_ELEMENT

		);

	} else if ( TYPE_MAP[ vkFormat ] === HalfFloatType ) {

		view = new Uint16Array(

			levelData.buffer,
			levelData.byteOffset,
			levelData.byteLength / Uint16Array.BYTES_PER_ELEMENT

		);

	} else {

		view = levelData;

	}
	//

	const texture = pixelDepth === 0
		? new DataTexture( view, pixelWidth, pixelHeight )
		: new Data3DTexture( view, pixelWidth, pixelHeight, pixelDepth );

	texture.type = TYPE_MAP[ vkFormat ];
	texture.format = FORMAT_MAP[ vkFormat ];
	texture.colorSpace = COLOR_SPACE_MAP[ vkFormat ] || NoColorSpace;

	texture.needsUpdate = true;

	//

	return Promise.resolve( texture );

}

export { KTX2Loader };