New GTAO in 4.24

With 4.24, GTAO was added, a new alternative to SSAO. It’s supposed to be a lot more accurate than SSAO.

With 4.24 Preview 1, I was successfully able to test GTAO, and it looked very good. The only problem I had was that it didn’t correctly work in VR, GTAO was only visible on one eye and the other eye didn’t have any AO.

But after 4.24 Preview 2, I could no longer get GTAO to work at all - enabling it just doesn’t do anything any more. Enabling it should be possible simply by doing

r.AmbientOcclusion.Method 1

Doing that in 4.24 Preview 1 did disable SSAO and enable GTAO correctly. Doing it in 4.24 Preview 2 and Preview 3 and Preview 4 just makes all AO disappear, GTAO doesn’t appear.

Did anyone have more success in the recent preview versions with using GTAO? Could anyone from Epic maybe chime in about how to enable it?

I’ve gotten GTAO working on 4.24p1 myself, but not particularly succesfully.

The above is my scene being rendered in 4.24p1 using GTAO. The below with SSAO.

The obvious issue here is the massive blurring going on when using GTAO. It’s as if the AO blur pass is being applied to (SceneColor*AOMask), rather than the AO buffer.

I haven’t tried GTAO since, but it does seem like Epic has quietly removed any mention of GTAO from the 4.24 Preview thread since then. I’m quite sure it was under rendering before.

I wonder if its a matter of not being ready or a patent issue :expressionless:

GTAO seems to be flat out removed in 2.24

Hey, guys.
Developed light studio setup for Unreal Engine 4.24
Link project:

First LPV and now this,all we have left are RT via RTX or of course, dynamic lighting,while the most costly ( and likely will lose bit audiences) especially on large-huge worlds, is ‘ok’ -

GTAO *is *in 4.24…

You need to enable it by r.AmbientOcclusion.Method 1. Some settings in the Post-Process Volume will affect GTAO as well, like Quality, Intensity, Static Friction, etc. But, GTAO is done at 50% resolution by default which can cause some ‘inverted halos.’ You can switch it back to full-res, at a cost obviously, with r.GTAO.Downsample 0. You can also toggle off the spatial or temporal filters with the same r.GTAO string, but disabling them will negatively impact the visual quality of GTAO(especially the spatial filter).

Clearly a typo above, no way anyone is using 2.24 o_0,anyway, so is this to replace dynamic lighting,would be nice if gtao was global and maybe poor ISh mans RT ?

BTW is this still ‘reelvant’ :

“” Originally posted by Tim Hobson View Post
To my knowledge, it’s only available for Console development and included in our Console Release Notes. If you have access to UDN with console development entitlements, you’ll be able to check those notes.
In 4.23 the new AO method automatically replaced SSAO when enabling SSGI. In 4.24 however, when you enable SSGI all AO is broken which renders SSGI useless until that is fixed. You can still see how AO changes in buffer view but in lit mode, it’s not there. "

There are 14 pages to sift through so if you know that would be ideal. :slight_smile:

It’s hard to tell by the quote what he meant exactly, but yeah, when you enable SSGI in 4.24 you get AO included that looks identical to GTAO(at default settings), but none of the AO controls actually affect the AO component of SSGI, so you’re kind of stuck with what you get right now. I posted in a previous thread that it’s really easy to modify the shader to boost the AO component, but it’s not intuitive and I couldn’t get the original AO Post-Process variables working.

Ty indeed,and btw following on twitter, impressive credentials , sounds like amazing jobs you’ve had, & cute dog there :slight_smile: Trying out 4.24.1 but Im getting nasty crashes , often and weird horrific performance problems I’m not seeing in 4.23, although 4.24 lighting is much better, too bad I crash so often , not usable - are you seeing any of that?

In 4.23 atm, but the errors had something to do with tesselation issues I believe,all on in scene components and off for landscape texture:


Assertion failed: TessellationFalloffSettings.UseTessellationComponentScreenSizeFalloff == SceneProxy->UseTessellationComponentScreenSizeFalloff [File:D:/Build/++UE4/Sync/Engine/Source/Runtime/Landscape/Private/LandscapeRender.cpp] [Line: 671]


Ya it was , just in case you have any idea, and I did file a bug just in case.


I have found a bit more info on this.

Problem with AO component of SSGI in 4.24 appears to be that the bounce light from skylight removes AO as if the surface is lit by a directional light.
To confirm this I have enabled SSGI and set GI intensity to 0 in post processing volume. AO shows up.
Setting GI intensity back to 1 removes all AO. I have attached the images below.

Ideally skylight’s light bounce should not reduce AO intensity by any amount (as in 4.23).
Following images are both from 4.24.1

After all, I’m not sure if AO component of SSGI is the new GTAO. But is the most accurate AO solution I’ve ever seen.

Edit: Edit: Just a correction. Skylight’s light bounce should reduce AO intensity in case GI intensity is manually increased. But on default GI intensity of 1 it shouldn’t completely take out all AO.

Does this work for large world world comp projects ? Just wondering,as no matter when I choose1,0 or inbetween,I see no differences in shadows, light- OR must I disable something else to get there with this enabled?

Well, technically having it “removed” is “correct”. But might not at all be what’s wanted in terms of art direction. A few art directable parameters would probably do well here.