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odd SSAO 'erasure' when object moves in front of the effect

PostPosted: Wed Sep 13, 2017 7:42 pm
by darbotron
Hi

I purchased your SSAO solution yesterday, it looks great in the test scene :)

There does however seem to be a slight issue with it, in that the SSAO contribution from objects closer to the camera seems to overwrite that of objects further away.

Here's 3 snips of screenshots which show what I mean, in these screenshots, the object is moved parallel to the camera plane from left to right so that it occludes the ssao darkened area in the corner of the room.

This shows the ssao in the corner of the room before the object moves in front

00.png
before overlap, corner fully darkened by ssao
00.png (147.18 KiB) Viewed 3160 times


First noticeable "anti artefact" - ssao darkening on wall to right of corner (in the magenta box) is 'erased' (or at least significantly lightened) as the object is approaches a point where it will occlude the ssao darkened area

01.png
ssao darkening on the wall to the right of the corner is 'erased' as the abject approaches
01.png (144.77 KiB) Viewed 3160 times


Second "anti artefact" - ssao darkening in the corner visible immediately above the object is 'erased'

02.png
ssao darkening above the object is 'erased'
02.png (143.21 KiB) Viewed 3160 times


The distance at which this 'erasure' effect as shown in the second image starts to occur seem to be directly proportional to the 'Radius' parameter on the inspector UI, and it looks to be as if the SSAO calculations from the object closer to the camera (but not close enough to anything to cause SSAO darkening) might be overwriting the SSAO darkening in the corner behind it.

This might be deliberate but it appears to me to be incorrect & might easily have escaped your notice, especially as there is nothing moving about in the demo scene :)

Alex

Re: odd SSAO 'erasure' when object moves in front of the eff

PostPosted: Mon Sep 18, 2017 4:22 pm
by Ricardo Teixeira
darbotron wrote:Hi

I purchased your SSAO solution yesterday, it looks great in the test scene :)

There does however seem to be a slight issue with it, in that the SSAO contribution from objects closer to the camera seems to overwrite that of objects further away.

Here's 3 snips of screenshots which show what I mean, in these screenshots, the object is moved parallel to the camera plane from left to right so that it occludes the ssao darkened area in the corner of the room.

This shows the ssao in the corner of the room before the object moves in front

00.png


First noticeable "anti artefact" - ssao darkening on wall to right of corner (in the magenta box) is 'erased' (or at least significantly lightened) as the object is approaches a point where it will occlude the ssao darkened area

01.png


Second "anti artefact" - ssao darkening in the corner visible immediately above the object is 'erased'

02.png


The distance at which this 'erasure' effect as shown in the second image starts to occur seem to be directly proportional to the 'Radius' parameter on the inspector UI, and it looks to be as if the SSAO calculations from the object closer to the camera (but not close enough to anything to cause SSAO darkening) might be overwriting the SSAO darkening in the corner behind it.

This might be deliberate but it appears to me to be incorrect & might easily have escaped your notice, especially as there is nothing moving about in the demo scene :)

Alex


Greetings,

Sorry for the delayed reply, we have a few Forum issues that we still need to ironout. For direct support, feel free to contact us via [email protected]

Unfortunately, you've stumbled upon one of the common SSAO limitations. Although the effect is extremely fast, it does have a few issue such as occluded artifacts or even incorrect AO on the edge of your screen. You assumption is correct, the larger the radius, the more noticeable the issue will be.

Apologies for the inconvenience.

Thanks!

Re: odd SSAO 'erasure' when object moves in front of the eff

PostPosted: Mon Sep 18, 2017 10:41 pm
by darbotron
No Thanks for getting back to me :)

It's not really a deal breaker, but it might be worth listing it as a known issue / limitation of the shader - especially if there's no plan to fix it :)

Cheers,

Alex

Re: odd SSAO 'erasure' when object moves in front of the eff

PostPosted: Tue Sep 19, 2017 10:08 am
by Ricardo Teixeira
darbotron wrote:No Thanks for getting back to me :)
It's not really a deal breaker, but it might be worth listing it as a known issue / limitation of the shader - especially if there's no plan to fix it :)
Cheers,
Alex


Hello,

Awesome, happy to know that it's not a deal breaker. Unfortunately, it's a limitation of the actual technique, also present in similar solutions. Screen-space effects are awesome but there's always an expected compromise.

We actually plan to replace the technique used with something more modern and efficient soon.

Stay tuned!