How to use RenderTarget texture as mipmaps?

Questions
1

As the title says, I want to customize the mipmap, so I specify the array to texture.mipmaps. The following is my code. Since there is no similar implementation in the documentation and example, I have not yet figured out how to implement it.

const envHdr = useEnvironment({ files: RES.texture.hdr })
  envHdr.generateMipmaps = true
  envHdr.minFilter = LinearMipMapLinearFilter

  const fbo = useFBO(envHdr.image.width, envHdr.image.height, {
    generateMipmaps: false,
    minFilter: LinearMipMapLinearFilter,
    magFilter: LinearFilter,
  })
 
useEffect(() => {
    if (!isInit.current) {
      isInit.current = true
      const mipmaps: Texture[] = []
      gl.setRenderTarget(fbo)
      fullScreenQuad.render(gl)
      for (let i = 1; i < 5; i++) {
        const mipmapsFbo = new WebGLRenderTarget(envHdr.image.width >> i, envHdr.image.height >> i, {
          generateMipmaps: false,
        })
        uniforms.uMipmapLevel.value = i
        uniforms.uRoughness.value = 0.2 * i
        uniforms.uSamples.value = Math.max (8096, uniforms.uSamples.value * 2)
        gl.setRenderTarget(mipmapsFbo)
        fullScreenQuad.render(gl)
        mipmaps.push(mipmapsFbo.texture)
      }
      gl.setRenderTarget(null)
      fbo.texture.mipmaps = mipmaps
    }
  }, [])

After doing these preparations, I sampled fbo.texture through textureLod in the shader, but the result was always completely black.

3

maybe needs a fbo.texture.needsUpdate = true after you set mipmaps?

4

I tried it. It doesn’t work. I will make a demo later so anyone can debug it.

5

here is demo:custom mipmaps test