Fill a Data3DTexture with texels from a noiseshader

the last few days have been quite exhausting but it was worth it. I now understand webgl2 shader much better.

now i face the next challenge. I want to create a 3D texture. With a shader I could use powerful noise functions. But the question that arises for me is the following: how do I get the texel datas from the shader, which are in the GPU, into my Data3DTexture?

maybe this pseudocode will help to better illustrate what I want

		//Values for the Data3DTexture
		const size = 128;
		const data = new Uint8Array( size * size * size );
		// what I imagine is a shader which generates the texels for the Data3DTexture
		const FS =`
		in int size;	//x, y, z
		out vec4 Color;
		someNoisefunction(vec3 coord){
		void main(){
			ivec3 pixel = ivec3(; //something like that but i need a webgl2 equivalent
			Color = texelFetch(someNoisefunction(pixel), pixel);
		data = reseive all texels from shader
		//now create Data3DTexture 
		const texture = new THREE.Data3DTexture( data, size, size, size );

does anyone know of an example in which a Data3DTexture is filled using a shader?