After many years I picked up on the X-Series again (starting with X3TC) and already lost myself to visually enhance the game to my personal liking. My recent efforts aim to achieve a rather realistic look of the (undouptedly beatiful) space landscape of the vanilla game. Changing the textures of planetary surfaces and atmospheres already yields good results. However I struggle to ensure that far away interstellar nebulae are being displayed behind the comparatively close by planets of a system instead of obscuring them.
MY QUESTION:
Where/How does the game store the information, whether a planet is displayed as a foreground feature (obscuring potential background nebulae) or as a background feature (being obscured by said nebulae)?
WHAT I KNOW:
These informations are neither stored in the bob-files of the planet models nor in the TPlanets-files. I am also quite sure it is not stored in the TBackgrounds-files either..
I hope, that there are still some old modders around, who can answere such questions or at least give me a decisive hint

Many thanks in advance!