three.js/examples/jsm/helpers/TextureHelperGPU.js

import {
	BoxGeometry,
	BufferAttribute,
	Mesh,
	PlaneGeometry,
	Vector3,
} from 'three';
import { NodeMaterial, texture as textureNode, cubeTexture, texture3D, float, vec4 } from 'three/tsl';
import { mergeGeometries } from '../utils/BufferGeometryUtils.js';

class TextureHelper extends Mesh {

	constructor( texture, width = 1, height = 1, depth = 1 ) {

		const material = new NodeMaterial();
		material.name = 'TextureHelper';

		let colorNode;

		if ( texture.isCubeTexture ) {

			colorNode = cubeTexture( texture );

		} else if ( texture.isData3DTexture || texture.isCompressed3DTexture ) {

			colorNode = texture3D( texture );

		} else {

			colorNode = textureNode( texture );

		}

		const alphaNode = float( getAlpha( texture ) );

		material.colorNode = vec4( colorNode.rgb, alphaNode );

		const geometry = texture.isCubeTexture
			? createCubeGeometry( width, height, depth )
			: createSliceGeometry( texture, width, height, depth );

		super( geometry, material );

		this.texture = texture;
		this.type = 'TextureHelper';

	}

	dispose() {

		this.geometry.dispose();
		this.material.dispose();

	}

}

function getImageCount( texture ) {

	if ( texture.isCubeTexture ) {

		return 6;

	} else if ( texture.isDataArrayTexture || texture.isCompressedArrayTexture ) {

		return texture.image.depth;

	} else if ( texture.isData3DTexture || texture.isCompressed3DTexture ) {

		return texture.image.depth;

	} else {

		return 1;

	}

}

function getAlpha( texture ) {

	if ( texture.isCubeTexture ) {

		return 1;

	} else if ( texture.isDataArrayTexture || texture.isCompressedArrayTexture ) {

		return Math.max( 1 / texture.image.depth, 0.25 );

	} else if ( texture.isData3DTexture || texture.isCompressed3DTexture ) {

		return Math.max( 1 / texture.image.depth, 0.25 );

	} else {

		return 1;

	}

}

function createCubeGeometry( width, height, depth ) {

	const geometry = new BoxGeometry( width, height, depth );

	const position = geometry.attributes.position;
	const uv = geometry.attributes.uv;
	const uvw = new BufferAttribute( new Float32Array( uv.count * 3 ), 3 );

	const _direction = new Vector3();

	for ( let j = 0, jl = uv.count; j < jl; ++ j ) {

		_direction.fromBufferAttribute( position, j ).normalize();

		const u = _direction.x;
		const v = _direction.y;
		const w = _direction.z;

		uvw.setXYZ( j, u, v, w );

	}

	geometry.deleteAttribute( 'uv' );
	geometry.setAttribute( 'uv', uvw );

	return geometry;

}

function createSliceGeometry( texture, width, height, depth ) {

	const sliceCount = getImageCount( texture );

	const geometries = [];

	for ( let i = 0; i < sliceCount; ++ i ) {

		const geometry = new PlaneGeometry( width, height );

		if ( sliceCount > 1 ) {

			geometry.translate( 0, 0, depth * ( i / ( sliceCount - 1 ) - 0.5 ) );

		}

		const uv = geometry.attributes.uv;
		const uvw = new BufferAttribute( new Float32Array( uv.count * 3 ), 3 );

		for ( let j = 0, jl = uv.count; j < jl; ++ j ) {

			const u = uv.getX( j );
			const v = texture.flipY ? uv.getY( j ) : 1 - uv.getY( j );
			const w = sliceCount === 1
				? 1
				: texture.isDataArrayTexture || texture.isCompressedArrayTexture
					? i
					: i / ( sliceCount - 1 );

			uvw.setXYZ( j, u, v, w );

		}

		geometry.deleteAttribute( 'uv' );
		geometry.setAttribute( 'uv', uvw );

		geometries.push( geometry );

	}

	return mergeGeometries( geometries );

}

export { TextureHelper };