Ambient Occlusion in the GZDoom skybox

[Tormentor667]

Dear developers,

I am using a sector-based skybox (sector special 90, GZDoom skybox) in my map and the ambient occlusion portal level is set to two. Unfortunately the ambient occlusion is also applied to the skybox even though it shouldn't be, check the screenshot for an example.



Bug or wrong setup?

[dpJudas]

There used to be a check if the portal being drawn was a skybox and if it were then it wouldn't run SSAO on it. I guess it must have been accidentally removed during one of the refactors of that code.

[Graf Zahl]

He said "sector built". I don't think these get handled properly by the AO pass.

[Marisa the Magician]

If it's a cube why not make a proper skybox in gldefs?

And if there is other geometry inside it, you could just make it a "recursive" skybox. Where the rest of the map uses skybox pickers to have that as its sky, and then the sector sky itself would have its sky set to the gldefs skybox.

[Nash]

Yeah this is why I avoid fake skyboxes, as in - a physically square sector with textures applied.

As Marisa said, use real skyboxes (the GLDEFS one). If you need geometry, you can do them recursively. Skyboxeption!

[Graf Zahl]

These recommendations are just stupid, considering that this style of skybox is an official engine feature. What needs to be done is to disable SSAO on any skybox portal being rendered from an appropriately tagged sector.

[Tormentor667]

There used to be a check if the portal being drawn was a skybox and if it were then it wouldn't run SSAO on it. I guess it must have been accidentally removed during one of the refactors of that code.

I think that is what the “GZDoom Skybox Sector Special” was meant for, but it doesn’t work.

[Marisa the Magician]

I'm currently in the process of fixing this, see this thread. AO on skyboxes would be disabled by default and need to be enabled explicitly through a mapinfo flag.

[sinisterseed]

I was just about to make another thread about this, glad I didn't have to.

I experienced an identical issue when I played ZDCMP2, strange square-like lines on the sky. I assumed it was a mapping error or some strange video artifact initially, but apparently it's not. This really ruins the skies if you ask me, so I'm glad it's getting addressed.

[Graf Zahl]

ZDCMP'2's skybox is actual sector geometry, that won't be fully fixable.

[Enjay]

Purely out of interest, I'm wondering why the skybox in the OP is made from a sector anyway. Isn't it just a cube with textures applied to the sides? If so, why not define it in GLDEFS?

[Tormentor667]

Purely out of interest, I'm wondering why the skybox in the OP is made from a sector anyway. Isn't it just a cube with textures applied to the sides? If so, why not define it in GLDEFS?

Because you can add dynamic objects to such a sector-based skybox or alter the textures of said sector. There are so many possibilities if it is sector-based.

[Enjay]

So it isn't just a simple cube then - it has dynamic elements too. Got it.

BTW, if all you want to do is change a GLDEFS skybox texture, that can be done using the usual changesky ACS command and the name of the skybox as defined in GLDEFS. I've done it several times myself.

[Tormentor667]

Yes, but adding weather effects or models into the skybox is a bit trickier