Cannot set manual mipmaps for CubeTexture

Description of the problem

Code in “setTextureCube” seems to only handle mipmaps for compressed textures. If I replace code in path that uploads uncompressed texture with this code, it works for data textures.

var mipmaps = texture.mipmaps;
if (!mipmaps.length) {
	mipmaps.push(texture.image);
}
for ( var j = 0, jl = mipmaps.length; j < jl; j ++ ) {
	state.texImage2D( _gl.TEXTURE_CUBE_MAP_POSITIVE_X + i, j, glFormat, mipmaps[j][i].image.width, mipmaps[j][i].image.height, 0, glFormat, glType, mipmaps[j][i].image.data );
}

I haven’t tested it with different types of textures. I’d be willing to make a pull request but I have no idea how this is intended to work (plain javascript without types is pretty hard to read beyond some complexity). Is there some reason why this wasn’t handled? Which mipmaps should be used, those on CubeTexture or those on individual faces? (it also isn’t very helpful that documentation doesn’t specify what mipmaps on texture should be, ImageData or Texture? Maybe it would make things clearer)

Three.js version

• Dev
• r85
• …

[Mugen87]

Should be solved via #17072

[robertoranon]

This PR should do exactly what requested