my plan was to make an underground base and sink most of it into the terrain and turn the terrain off once the player enters the building but the player can not go down the stairs past where the terrain once was, I cant find anything in Lua about physics, is this static behavior or is there a workaround?

If you didn't see it in one of the demo games, then it will probably require a workaround. HideTerrain doesn't remove the terrain, lower it, or make it flat, so I think the behavior is normal and intended to work that way. The terrain editor is great for landscapes, but not for making basements, so it would be near impossible to make clean square hole to drop your building into. My immediate thought is that instead of "turning off terrain" you simply load another map for the underground base using JumpToLevel. When you enter the stairs leading down use JumpToLevel and start the underground level at the bottom of the stairs, or use an elevator so that it doesn't feel so much like loading another level to the player.

Hide Terrain does not turn off the physics for terrain.

What you can do is paint the terrain to the lowest point just above the water so AI will work and build your level above the terrain so your floor sits on what would be the terrain. You (the player) should be able to access all areas of your map and AI will walk and traverse on the terrain level.

AI walking on other then terrain should be getting started after the EBE is complete.

Defiantly a work around.

If you want to turn off the terrain for a bunker section, you would be best to carve the shape of the bunker into the terrain, then, place your bunker inside the cutouts. Then, once your player enters the bunker, you can have a trigger zone with a script attached to remove the terrain. The script would be goindoors.lua. Make sure you have another script at the exit points of the bunker (gooutdoors.lua). Both of these scripts are default and should be able to found in the scriptbank folder.

Hope this helps.

Cheers

Jay.

Don't know if this will help but if you check out my Die Glocke thread I managed to get AI on different levels by raising the ground to the floor levels giving the impression of an underground level ( not an easy task ) ..... Its all explained here ...and a demo to try ..

https://forum.game-guru.com/thread/215536

You can use the transport feature to transport yourself to the underground base. I would build your base somewhere away from your main map where it can't be seen. Have an entrance to the base and when you enter it, transport to the underground section. it doesn't need to be underground, but it will give the impression of it. You can hide your underground map behind terrain or billboards etc. I have done this before and as far as the player is concerned works fine. I used it in Subterranean Secret (a compo entry) ages ago, to help keep speed up in the main level by separating the interior of a building to a different location miles away on the map, so avoiding dropping lots of items in an already busy area.

That's exactly what I plan to do with my WIP, leading up to the bunker in my game is a wooded area with a few log buildings where you find the clues to locate the bunker entrance, once you get to the entrance you have to work out how to get in, at which point you're transported to the interior which is actually physically located on the far side of the map, helps with FPS and makes it so your entrance doesn't have to be on a mile high chunk of terrain.

Why not just have a level jump to a new map so only the entrance is on the first level .... that way you will have a clean map to make your bunker interior saving even more fps ..

And the nice thing is ...you can always jump back again to the original map with another level jump

Because players don't like loading screens, the more loading screens and smaller levels you have the more people get frustrated

Ye I guess so ..... I suppose it depends on how long it takes to get to the bunker ..... if its a good 30 mins to an hour of playing then a level load wouldn't really bother me to much...In fact I find it as YES !! achieved the first level .... Just idea's .... you can never have to many options