Distinct lightning for 3d Skybox?

[Arhurt]

Hey guys!

Let me tell you my idea: I want to make my map normally, with a skybox as usual, and a 3d skybox as well. But then, there is going to be an underground area, a cave, and I'd like to make it feel as if a very large underground complex loosely based on some Guild Wars dungeons ([1], [2]), and in order to do this, I'd need to model a large underground room in the 3Dskybox.

Now, I know that the 3Dskybox only shows where there is the actual skybox (or am I wrong?) and I know that the skybox will light up everything, so how can I keep the sunlight from being projected in my cave?

I have tought of enclosing the model (imagine modelling something from inside out, with all normals inverted), since I'll only be able to see inside the "bubble" and it is enclosed, it won't be lit.

I could also add a large brush to block the sunlight, but that could be costly performance-wise.

So, am I delusional? Or is it possible?

Thanks in advance, take care!

 

[Earl]

Yeah, just make a brush to block light entering the cave. For clarification, its not the 3D skybox that lights the map, its the 2D sky from the 3D skybox that actually lights the map. In my map. objects in the 3D skybox cast shadows in the actual game area.