Arghh.. How do I explain this.
Think of it as 3 layers. One at the bottom for people looking UP, one at the top for people looking DOWN, and one thick one in the middle for people flying through it.
AH already has the middle layer, you fly through it and things become hazy and vis range becomes hard to make out.
Adding the first and third layer of clouds, is a simple 2D image. That way, when you look at the clouds, it has the ILLUSION of being real clouds, and not just a layer of haze.
That's how it is in Jane's pretty much, and if AH were to take it up a notch and add water effects like Wings of Prey, I would spend an entire week just flying at cloud level.