[3.5.0] Skyboxes are affected by SSAO

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[3.5.0] Skyboxes are affected by SSAO

Postby Marisa Kirisame » Thu Aug 09, 2018 3:19 pm

This screenshot was taken in Blade of Agony. With "Portals with AO" set above 0.

I remember this was fixed way back, and still works fine even all the way up to 3.4.1, but it appears to be back now. Could be that something screwed up after the modern branch merge?
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Re: [3.5.0] Skyboxes are affected by SSAO

Postby Graf Zahl » Thu Aug 09, 2018 3:38 pm

BoA's skyboxes are regular sectors with a slightly adjusted texture mapping. I don't think SSAO can catch this.

Overall, I find that SSAO doesn't really work that great. On very detailed maps it creates a lot of aliasing-like artifacts.
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Re: [3.5.0] Skyboxes are affected by SSAO

Postby Percival Cunningnat » Thu Aug 09, 2018 7:12 pm

GZdoom 3.4 did not do this even with "Portals with AO" set to 4 .
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Re: [3.5.0] Skyboxes are affected by SSAO

Postby Marisa Kirisame » Fri Aug 10, 2018 6:55 am

I agree that it's bad and wrong to do skies like this, but it still stands that SSAO did "catch" this before, though.
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Re: [3.5.0] Skyboxes are affected by SSAO

Postby Enjay » Mon Aug 13, 2018 7:08 am

For what it's worth, I noticed this when testing game slowdown in Temple of the Lizardmen II

Image

See that slight shadowy curve across the sky looking a bit like an upside down grey rainbow?

The skybox in the map is constructed like this:

Image

A central octagon(ish) shape with slopes creating a dome-like structure on which the sky texture is used.

And, like already mentioned, going back to an old Git build that I have lying around, the AO "rainbow" is not present.


However, it's also worth pointing out that, although in a skybox like this and the one from BoA, AO is not desirable across the sky, there may well be plenty of examples where it would be desirable. e.g. Something using an effect like Gooberman used to have a spaceship flying into a structure that was actually a moving skybox camera would look much better with AO in the skybox than without it. So it possibly shouldn't just be a case of "if the view is from a skybox camera, don't use AO" (if that is even possible). Or, maybe have some way of flagging skybox cameras so that they do "see" AO (defaulting to not seeing I suppose).
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Re: [3.5.0] Skyboxes are affected by SSAO

Postby Enjay » Mon Aug 13, 2018 7:19 am

Digging a little bit further, I *think* maybe it's to do with light levels and how AO might have changed with them. The Lizardmen skybox uses a light level of 255 in its sectors. I'm guessing that, previously, in areas like this, there was no visible AO effect on sectors with maximum brightness. I had a feeling that I was noticing this in other areas of maps too. Like, if I'd had an alcove lined with LITE5 textures and set to be very bright, I didn't think that it was looking quite so bright in 3.5.0 as it was before. Looking at it again, I think that it might be that in bright sectors like that (255 or near to it), the SSAO effect was far less visible in earlier versions than it is with 3.5.0. So, perhaps it's not a skybox and AO related thing at all, but a sector brightness and AO one instead.

[edit] or maybe not. These screenshots don't show much difference between the old version and 3.5.0

old git version
Image

3.5.0
Image

In the map, the walls and ceilings of the alcoves are made from a texture that is solid 255, 255, 255 white. The light level in the alcoves is 255. I was expecting none (or almost no) AO effect in the git version versus 3.5.0 but that doesn't seem to be the case.


The git version used was g3.3pre39-g2f45218 - so not very recent.

[/edit]
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