Thanks for the hint, I didn't knew I had to serialize Object3D before adding it to my World.
Now, I serialize a clone of my Object3D (using cloneObject() ) right after loading the original .obj file.
I can then add this cached object to a new world where it is rendered.
Nevertheless, now a new problem occurs:
When using the "normally" loaded (via .obj file) Object3D, highlights and shades look fine.
But when I use the cached Object3D, no highlights and shades are rendered. The color of my (monochromatic) texture is simply applied to the whole Object3D. I use exactly the same setup of the world, lights and objects as before.
Do I have to obey a specific order like before? Any hints, what else might be the problem?
Thanks!