Ambient Occlusion in Morrowind

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ajira2
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Ambient Occlusion in Morrowind

Post by ajira2 » 05 Apr 2018, 13:11

Is feasible this feature in Morrowind?

As an optional checkbox in GUI adjust graphics?

I imagine adjusting graphics in Morrowind with predefined settings like low, medium, high and ultra and with ultra the checkbox of ambient occlusion gets checked automatically?

What do you think of it?

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Last edited by ajira2 on 06 Apr 2018, 11:27, edited 1 time in total.

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AnyOldName3
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Re: Ambient Occlusion in Morrowind

Post by AnyOldName3 » 05 Apr 2018, 14:28

What type of ambient occlusion are you meaning? It can refer to a few different things (usually attempts to approximate Full Global Illumination, which is sometimes too expensive even for non-real-time renderers), including:
  • Objects having an AO map which makes dents and divets darker. This is more or less what the dark map is for in Morrowind.
  • Screen-space post-process effects like SSAO and HBAO, which darken pixels which are further away from the camera than their neighbouring pixels. OpenMW doesn't support this right now, but probably will at some point.
  • Baking AO data for each level (or cell for Morrowind) beforehand. This is far less likely to ever end up in OpenMW, and if it does, it'll be in the far future.
  • Things like Radiosity which compute diffuse-diffuse interreflections in an attempt to actually have an accurate model for ambient light and where it's coming from. These are very rare in real-time applications (an incredibly simplified and streamlined version was used in Battlefield 3, for example, but to my knowledge, not in its sequels) as getting good results is either very slow, or requires a tonne of work from the engine developers and people making the assets in the first place.
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drummyfish
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Re: Ambient Occlusion in Morrowind

Post by drummyfish » 05 Apr 2018, 15:42

I suppose we're talking about SSAO which is common in most modern games and would be possible in OpenMW. It's a postprocessing/multi-pass effect - I've been talking about bringing postprocessing into OpenMW some time ago and there have been threads here, such as this one. Basically we need to find someone willing to implement that :)

EDIT: It wouldn't be just about implementing this one effect, but rather a whole subsystem for all kinds of effects, which AO would be part of. We could then also have effects such as bloom, color corrections, god rays etc.

ajira2
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Re: Ambient Occlusion in Morrowind

Post by ajira2 » 06 Apr 2018, 10:56

Thank you for your answers, yes I was refering to SSAO and HBAO (which one is better?)

EffectCompositor would be amazing, I hope scrawl or someone knowledgeable has time for this in the future.

PS: I'm sure god rays would look amazing :)

PS2: Judging by this image seems that HBAO is superior to SSAO, right?

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drummyfish
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Re: Ambient Occlusion in Morrowind

Post by drummyfish » 06 Apr 2018, 12:55

ajira2 wrote:
06 Apr 2018, 10:56
(which one is better?)
SSAO in the primitive implementation is a very basic algorithm which however fails miserably very often and I'm actually hating it most of the times. I think it's used in ESO. HBAO works better and I think it's also slower, but honestly don't know more details, will have to take a look at it.

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AnyOldName3
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Re: Ambient Occlusion in Morrowind

Post by AnyOldName3 » 06 Apr 2018, 14:25

When SSAO was 'discovered' (or maybe invented) lots of games made its effect far too strong and didn't necessarily tune it properly because it made screenshots look good, even if it wasn't particularly (or even slightly) accurate. It's supposed to have a falloff as the depth difference between regions increases exactly to avoid the problems shown in those Far Cry 3 screenshots, but it looks like Ubisoft configured it to be too far away. It can look pretty good if it's set up properly.

HBAO and HBAO+ are more accurate and require less tuning, but slower. Most games that implement them don't actually implement them, though, instead just importing the implementation from NVidia's GameWorks, which is closed-source, Direct3D-only and generally considered to have been created with anti-consumer intent. There should be enough information in the papers NVidia made about them to create an open source OpenGL compatible version, though.

VXAO is apparently not a screen-space post-process effect but instead a voxel-based algorithm that works in world space, so it should be pretty accurate, but it claims to be 10 times slower than HBAO+. It's also a GameWorks technology, so available only as closed-source, binary-only Direct3D implementation, and unlike HBAO+, there don't seem to be enough details released to create a fast implementation that works without more or less starting from scratch.

Also, with those Tomb Raider screenshots, I'm not sure they're real. To me, it looks like it's the same screenshot with the contrast increased and brightness decreased. Lighting that shouldn't be affected by AO, just by the shadow map, seems to be darkened in the right two images.
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Br0ken
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Re: Ambient Occlusion in Morrowind

Post by Br0ken » 06 Apr 2018, 14:48

Looks like GTAO is good alternative.

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Re: Ambient Occlusion in Morrowind

Post by drummyfish » 06 Apr 2018, 15:09

AnyOldName3 wrote:
06 Apr 2018, 14:25
It's supposed to have a falloff as the depth difference between regions increases exactly to avoid the problems shown in those Far Cry 3 screenshots.
I know it was over the top in Far Cry, I meant to show clearly what it looks like when it fails. However even with falloff the problem is still there, just a little reduced: there's a problem with lack of information in the depth map, the algorithms simply falsely assigns occlusion where there should be none (e.g. around a character in front of a wall). As I said, take a look at TES Online AO, it still looks pretty bad even nowadays (e.g. the leftmost guy's hat):

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AnyOldName3
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Re: Ambient Occlusion in Morrowind

Post by AnyOldName3 » 06 Apr 2018, 15:46

It seems that it's just a slightly enhanced version of HBAO+ so that you can declare it to be physically-based. It won't be even slightly as good as the world-space voxel technique, and while we're using a non-physically-based shading and lighting model anyway, I'm not sure that doing all that work over HBAO+ would be the highest priority.

There's also the minor issue that despite being a screen-space technique, GTAO seems to not be a post-process effect, but instead something you're supposed to run in a deferred renderer in between the geometry and colouring in stages. The same might be true of HBAO+, but then I also suppose that if you wanted SSAO to look as good as it possibly could you'd run it the same way.

Regarding TES Online, I don't think anyone's ever tried to argue that it's had state of the art graphics or even particularly good graphics, except in that one bit of promotional material where they were showing off how much better the Morrowind expansion looked than Morrowind itself.
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Br0ken
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Re: Ambient Occlusion in Morrowind

Post by Br0ken » 06 Apr 2018, 20:13

Yes, I agree that now non-physical SSAO algorithm will be more viable. But I hope to see some PBR in future... ;)
As I know Scalable Ambient Obscurance also gives a good result and it's more cheap than HBAO.

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