[BUG/FEATURE] TAA is transforming road traffic into ghosts (self-cancelling moving pixels)

Brief description of the issue:

The TAA implementation is based on pixel motion vectors (most likely). However this is causing any moving feature in the simulator self-canceling itself.

When in VR, it makes nearly all vehicles disappearing except big white trucks (they are slightly more visible due to the larger pixel footprint on the screen and TAA is “only” eroding the edges)

I believe this bug is also one of the reason people have been reporting road traffic doesn’t seem very crowded in 2D either.

Provide Screenshot(s)/video(s) of the issue encountered:

n/a (see below)

Detail steps to reproduce the issue encountered:

The nature of the TAA algorithm is self-explanatory as to why this is ghosting moving vehicles, nevertheless, to repro, just start FS2020 in VR with road traffic (try 100%), take off, fly over a highway at 1000ft to 2000ft AGL, and look through the cockpit window down below. Unless this is a specific bug on my system, which I doubt, there is no way you can’t see this.


[31JUL2021]
And now there is at least a technical explanation to me (timestamped YT video below):

Inside Microsoft Flight Simulator - Xbox Ports, Performance, PC Optimisations - The Asobo Breakdown!

In short, I suspect the very nature of the TAA implementation using accumulation buffers is why every single moving object in the game is self-canceling its own pixels. I do hope they’ll figure a way to solve this, maybe in accumulating all moving objects in a separate buffer over less frames?!

In any case, I’d like to thank you Lionel for your invaluable and honest insights, I’d really like to see you more in the Q&A or other videos!

I use TAA for VR as well and this isn’t something I have noticed before. All my road traffic looks fine in VR. I have just checked again and I am not seeing this issue- I can see all sizes of vehicles without any transparency. It seems to be an interesting bug! FYI I use Oculus rift CV1.

Edit: Update…I am actually seeing this issue at the altitudes you describe, but not below say 900 ft agl. I always assumed it was due to the poor resolution of the CV1

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To me this is TAA motion vector pixel counter-canceling car pixel motion and therefore making them appearing “ghostly”. Because of how this works, it is eroding moving car pixels starting from the edges (bumpers, given the car pixel path), and it is making smaller cars even nearly invisible as a consequence.

I’ve tried capturing through the lens to show the difference. It is subtle and this might look like video compression artefact but it is not. Please make sure to watch these full screen

No AA:

Comment:
The red car is suffering compress artefacts but white cars shape is clearly defined and just jiggling because there is no AA.

TAA:

Comment:
Clearly visible on the white car traversing the intersection from left to right. You can also notice a “green” car coming from the left road and driving near the trees, and I believe it is only appearing green because of TAA projecting the green leafs over the moving car pixels.

NB: These were shot at 1000ft AGL in order to get enough pixels on the video (the forum is limiting to 5MB and I don’t think I could have host a 4K file here because of this), but you can see cars from much higher altitude otherwise and in this case the ghosting is so strong it makes them nearly invisible when they’re moving fast.

2 Likes

I believe this is related in fact:

  • With a lower resolution headset you need to be lower in order for a car rendering over a certain amount of pixels.

  • With a higher resolution headset like the G2, you need to be higher for the same amount of pixel coverage.

But in turn you do see the same problem which is already a good sign it is not just my imagination (I never doubt this though).

As a matter of fact, in looking for a simple TAA explanation to post in this discussion for others to better understand what this problem is about, I’ve found the wiki page simple enough and explaining exactly what is happening in my videos:

Temporal anti-aliasing - Wikipedia

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Since my last post I’ve been further revising and re-evaluating my VR recommendations and this problem is still showing whenever using TAA, which seems consistent with how the algorithm is working. When using no-AA or FXAA it is definitely not “ghosting” road traffic but at the expense of flickering.

2 Likes

I’ve updated the OP with more recent info:

PS: regardless of the topic (TAA is transforming…) I’d recommend everyone to watch this video. It has tons of technical details about what’s going on behind the scene and it is excellent in my opinion.

Thank you again Lionel for sharing your insights!

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i’m baffled, at this point either “everyone” (user) gave up on reporting or tracking any bugs or just no one’s noticing this?

@Ju1ius2416
This is a very good question… but who cares anymore?

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After a year of release and hundreds of bug reports, I’ve given up. Before SU5, at least we had decent graphics. After SU, my VR is a shimmer fest especially in bright day light, and unfliable. Asobo simply said ‘unable to reproduce’ and moved on. Honestly, they have not touched the VR side since the release and I have very little hope that they will do anything at this point. Intead of squashing bugs, they are busier squashing legitimate ‘bug reports’. They are more interested in explanding their market place revenue and XBOX expansion. And I don’t care anymore.

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I was wondering indeed, because just wearing a VR headset in the Asobo 787 and you can’t notice anything else than this right away:

[BUG] FS2020 using 3D cockpit camera in VR - wrong horizontal plane rotation (ex: FBW A320, SALTY 747, ASOBO 787, SDK SAMPLE)

1 Like