What is SSAO?

[Sunshine & Rainbows]

I'm turning it off for now because I don't know what it is and I want to ensure reasonable performance.

[cSg|mc-Hotsauce]

http://en.wikipedia.org/wiki/Screen_space_ambient_occlusion

[Sunshine & Rainbows]

Thanks.

Screen space ambient occlusion (SSAO) is a rendering technique for efficiently approximating the computer graphics ambient occlusion effect in real time. It was developed by Vladimir Kajalin while working at Crytek and was used for the first time in a video game in the 2007 Windows game Crysis, developed by Crytek and published by Electronic Arts.

The algorithm is implemented as a pixel shader, analyzing the scene depth buffer which is stored in a texture. For every pixel on the screen, the pixel shader samples the depth values around the current pixel and tries to compute the amount of occlusion from each of the sampled points. In its simplest implementation, the occlusion factor depends only on the depth difference between sampled point and current point.
Without additional smart solutions, such a brute force method would require about 200 texture reads per pixel for good visual quality. This is not acceptable for real-time rendering on current graphics hardware. In order to get high quality results with far fewer reads, sampling is performed using a randomly rotated kernel. The kernel orientation is repeated every N screen pixels in order to have only high-frequency noise in the final picture. In the end this high frequency noise is greatly removed by a NxN post-process blurring step taking into account depth discontinuities (using methods such as comparing adjacent normals and depths). Such a solution allows a reduction in the number of depth samples per pixel to about 16 or fewer while maintaining a high quality result, and allows the use of SSAO in soft real-time applications like computer games.
Compared to other ambient occlusion solutions, SSAO has the following advantages:
Independent from scene complexity.
No data pre-processing needed, no loading time and no memory allocations in system memory.
Works with dynamic scenes.
Works in the same consistent way for every pixel on the screen.
No CPU usage – it can be executed completely on the GPU.
May be easily integrated into any modern graphics pipeline.
Of course it has its disadvantages as well:
Rather local and in many cases view-dependent, as it is dependent on adjacent texel depths which may be generated by any geometry whatsoever.
Hard to correctly smooth/blur out the noise without interfering with depth discontinuities, such as object edges (the occlusion should not "bleed" onto objects).

I think I'll have to read that several times.

[James_789]

In short it is a more advanced anti aliasing but it uses more VRAM and affects performance much more than FXAA or traditional AA.

[SabreToothedSloth]

Originally posted by Prentice:

In short it is a more advanced anti aliasing but it uses more VRAM and affects performance much more than FXAA or traditional AA.

That's Supersample AA, he asked about SSAO

[Risule]

It's not antialiasing (AA). It's a shading method that helps objects blend better into the scene by adding "shadows" making it look a bit more realistic. Basically to places where should be less light in real life.

[fede01_8]

Ok, so in plain English what it is?

[Shin Dan]

Originally posted by fede01_8:

Ok, so in plain English what it is?

Really, really pretty.

[Sunshine & Rainbows]

Originally posted by Ríšule:

It's not antialiasing (AA). It's a shading method that helps objects blend better into the scene by adding "shadows" making it look a bit more realistic. Basically to places where should be less light in real life.

That's kinda what I thought it was.

[James_789]

Originally posted by Daniel:

Originally posted by Prentice:

In short it is a more advanced anti aliasing but it uses more VRAM and affects performance much more than FXAA or traditional AA.

That's Supersample AA, he asked about SSAO

I am really sorry. Thanks for the correction, I thought s/he was asking about SSAA and not SSAO, my bad. I should have read more carefully.

Originally posted by Ríšule:

It's not antialiasing (AA). It's a shading method that helps objects blend better into the scene by adding "shadows" making it look a bit more realistic. Basically to places where should be less light in real life.

Ríšule has answered the question correctly. Additionally you can read more about the additional types of anti-aliasing technologies on this webpage[pcgamingwiki.com]. It is very well and clearly explained there.

If your GPU can handle it both SSAO and SSAA greatly increase the visuals of the game.

[BlastThyName]

It's worth nothing that TR uses HDAO when the ambient occlusion setting is set to ultra.
It's better, more subtle but also more expensive !
SSAO does the job just fine for me.

[-{Geo}- Cegorach]

It transforms Human Character in to a Walking Lightbulb.