Looks like you need to bake the lighting.
https://developer.valvesoftware.com/wiki/SteamVR/Environments/Environment_Tutorial:_Hammer_and_Basic_Lighting#Basic_Lighting

Originally posted by Rectus:

Looks like you need to bake the lighting.
https://developer.valvesoftware.com/wiki/SteamVR/Environments/Environment_Tutorial:_Hammer_and_Basic_Lighting#Basic_Lighting

I did do that already.

Originally posted by Rectus:

Looks like you need to bake the lighting.
https://developer.valvesoftware.com/wiki/SteamVR/Environments/Environment_Tutorial:_Hammer_and_Basic_Lighting#Basic_Lighting

Sorry, I guess I said that wrong, when I say rebuild, I meant re-bake.

https://photos.app.goo.gl/2vQ24jqAdGXVbyFy8
Here's a view of the cubemaps as well.
I had at one point also tried making one giant cubemap that encompassed the entire map, including exterior, but that did not work either, it looked the same.

Cubemaps and light probe volumes only affect specular lighting and dynamic objects respectively. they don't affect how diffuse lighting is baked onto static surfaces.

From your images it looks like no indirect lights are baked. What settings are you using on your light_environment?

Originally posted by Rectus:

Cubemaps and light probe volumes only affect specular lighting and dynamic objects respectively. they don't affect how diffuse lighting is baked onto static surfaces.

From your images it looks like no indirect lights are baked. What settings are you using on your light_environment?

Originally posted by Rectus:

Cubemaps and light probe volumes only affect specular lighting and dynamic objects respectively. they don't affect how diffuse lighting is baked onto static surfaces.

From your images it looks like no indirect lights are baked. What settings are you using on your light_environment?

My settings are the default for the light_environment. Indirect lighting is set to baked.

It seems almost as if only the walls cast shadows, it's strange.

Oh, I'm an idiot! That was exactly it. I checked under the materials, somehow, on my roof material, "Do Not Cast Shadows" was turned on.

Are you baking the lighting from the menu bar with Preview Baked Lighting -> Bake All Lighting?

https://photos.app.goo.gl/XdANWr3K6fAR9uHVA
Now it looks a lot nicer!

Originally posted by Rectus:

Are you baking the lighting from the menu bar with Preview Baked Lighting -> Bake All Lighting?

Yes, I am.

Guessing the shadows being pitch black is caused by vertices being occluded and low vertex density. You may need to clean up your geometry to get it to light properly, as well as adding some subdivisions.

You can also get better (and vertex density independent) lighting resolution by using lightmapping instead of vertex lighting. It is enabled by compiling the map itself with Custom settings, and checking the Generate Lightmaps option. It will only show up in-game, not in the editor. It can also take a very long time to generate depending on the resolution setting.

Originally posted by Rectus:

Guessing the shadows being pitch black is caused by vertices being occluded and low vertex density. You may need to clean up your geometry to get it to light properly, as well as adding some subdivisions.

You can also get better (and vertex density independent) lighting resolution by using lightmapping instead of vertex lighting. It is enabled by compiling the map itself with Custom settings, and checking the Generate Lightmaps option. It will only show up in-game, not in the editor. It can also take a very long time to generate depending on the resolution setting.

Ok, thanks.
Also, I added a bunch of lights, they seem to not always render, you have to be looking directly at them / within a range. Is there a way to fix this? Some areas appear dark because of this.

It's limited to 16 real-time lights visible at the same time. To get more, you will have to bake them. I don't think fully baking them works properly with vertex lighting, only when using the lightmapper.

Originally posted by Rectus:

It's limited to 16 real-time lights visible at the same time. To get more, you will have to bake them. I don't think fully baking them works properly with vertex lighting, only when using the lightmapper.

Ah ok, thanks.