Updated builds.

build/three.js

@@ -19626,6 +19626,78 @@
 			state.unbindTexture();
 		};
 
+		this.copyTextureToTexture3D = function (sourceBox, position, srcTexture, dstTexture, level) {
+			if (level === void 0) {
+				level = 0;
+			}
+
+			if (_this.isWebGL1Renderer) {
+				console.warn('THREE.WebGLRenderer.copyTextureToTexture3D: can only be used with WebGL2.');
+				return;
+			}
+
+			var _srcTexture$image = srcTexture.image,
+					width = _srcTexture$image.width,
+					height = _srcTexture$image.height,
+					data = _srcTexture$image.data;
+			var glFormat = utils.convert(dstTexture.format);
+			var glType = utils.convert(dstTexture.type);
+			var glTarget;
+
+			if (dstTexture.isDataTexture3D) {
+				textures.setTexture3D(dstTexture, 0);
+				glTarget = 32879;
+			} else if (dstTexture.isDataTexture2DArray) {
+				textures.setTexture2DArray(dstTexture, 0);
+				glTarget = 35866;
+			} else {
+				console.warn('THREE.WebGLRenderer.copyTextureToTexture3D: only supports THREE.DataTexture3D and THREE.DataTexture2DArray.');
+				return;
+			}
+
+			_gl.pixelStorei(37440, dstTexture.flipY);
+
+			_gl.pixelStorei(37441, dstTexture.premultiplyAlpha);
+
+			_gl.pixelStorei(3317, dstTexture.unpackAlignment);
+
+			var unpackRowLen = _gl.getParameter(3314);
+
+			var unpackImageHeight = _gl.getParameter(32878);
+
+			var unpackSkipPixels = _gl.getParameter(3316);
+
+			var unpackSkipRows = _gl.getParameter(3315);
+
+			var unpackSkipImages = _gl.getParameter(32877);
+
+			_gl.pixelStorei(3314, width);
+
+			_gl.pixelStorei(32878, height);
+
+			_gl.pixelStorei(3316, sourceBox.min.x);
+
+			_gl.pixelStorei(3315, sourceBox.min.y);
+
+			_gl.pixelStorei(32877, sourceBox.min.z);
+
+			_gl.texSubImage3D(glTarget, level, position.x, position.y, position.z, sourceBox.max.x - sourceBox.min.x + 1, sourceBox.max.y - sourceBox.min.y + 1, sourceBox.max.z - sourceBox.min.z + 1, glFormat, glType, data);
+
+			_gl.pixelStorei(3314, unpackRowLen);
+
+			_gl.pixelStorei(32878, unpackImageHeight);
+
+			_gl.pixelStorei(3316, unpackSkipPixels);
+
+			_gl.pixelStorei(3315, unpackSkipRows);
+
+			_gl.pixelStorei(32877, unpackSkipImages); // Generate mipmaps only when copying level 0
+
+
+			if (level === 0 && dstTexture.generateMipmaps) _gl.generateMipmap(glTarget);
+			state.unbindTexture();
+		};
+
 		this.initTexture = function (texture) {
 			textures.setTexture2D(texture, 0);
 			state.unbindTexture();

build/three.module.js

@@ -24943,6 +24943,80 @@ function WebGLRenderer( parameters ) {
 
 	};
 
+	this.copyTextureToTexture3D = function ( sourceBox, position, srcTexture, dstTexture, level = 0 ) {
+
+		if ( _this.isWebGL1Renderer ) {
+
+			console.warn( 'THREE.WebGLRenderer.copyTextureToTexture3D: can only be used with WebGL2.' );
+			return;
+
+		}
+
+		const { width, height, data } = srcTexture.image;
+		const glFormat = utils.convert( dstTexture.format );
+		const glType = utils.convert( dstTexture.type );
+		let glTarget;
+
+		if ( dstTexture.isDataTexture3D ) {
+
+			textures.setTexture3D( dstTexture, 0 );
+			glTarget = 32879;
+
+		} else if ( dstTexture.isDataTexture2DArray ) {
+
+			textures.setTexture2DArray( dstTexture, 0 );
+			glTarget = 35866;
+
+		} else {
+
+			console.warn( 'THREE.WebGLRenderer.copyTextureToTexture3D: only supports THREE.DataTexture3D and THREE.DataTexture2DArray.' );
+			return;
+
+		}
+
+		_gl.pixelStorei( 37440, dstTexture.flipY );
+		_gl.pixelStorei( 37441, dstTexture.premultiplyAlpha );
+		_gl.pixelStorei( 3317, dstTexture.unpackAlignment );
+
+		const unpackRowLen = _gl.getParameter( 3314 );
+		const unpackImageHeight = _gl.getParameter( 32878 );
+		const unpackSkipPixels = _gl.getParameter( 3316 );
+		const unpackSkipRows = _gl.getParameter( 3315 );
+		const unpackSkipImages = _gl.getParameter( 32877 );
+
+		_gl.pixelStorei( 3314, width );
+		_gl.pixelStorei( 32878, height );
+		_gl.pixelStorei( 3316, sourceBox.min.x );
+		_gl.pixelStorei( 3315, sourceBox.min.y );
+		_gl.pixelStorei( 32877, sourceBox.min.z );
+
+		_gl.texSubImage3D(
+			glTarget,
+			level,
+			position.x,
+			position.y,
+			position.z,
+			sourceBox.max.x - sourceBox.min.x + 1,
+			sourceBox.max.y - sourceBox.min.y + 1,
+			sourceBox.max.z - sourceBox.min.z + 1,
+			glFormat,
+			glType,
+			data
+		);
+
+		_gl.pixelStorei( 3314, unpackRowLen );
+		_gl.pixelStorei( 32878, unpackImageHeight );
+		_gl.pixelStorei( 3316, unpackSkipPixels );
+		_gl.pixelStorei( 3315, unpackSkipRows );
+		_gl.pixelStorei( 32877, unpackSkipImages );
+
+		// Generate mipmaps only when copying level 0
+		if ( level === 0 && dstTexture.generateMipmaps ) _gl.generateMipmap( glTarget );
+
+		state.unbindTexture();
+
+	};
+
 	this.initTexture = function ( texture ) {
 
 		textures.setTexture2D( texture, 0 );