What is it?
Screen Space Ambient Occlusion (or in SL commonly only known as Ambient Occlusion which is a combination of several features) is one of the most common and basic advanced shader features used to produce a more realistic scene, Screen Space Ambient Occlusion is used to give the scene more depth and fake 'secondary shadowing' in a cheap and affordable way, or simply to calculate Ambient Occlusion of a scene.
How does it look?
Notice the darkening around objects touching other objects? It is a bit hard to see as these building parts already bake Ambient Occlusion partly into their textures but you can clearly see that especially the curvy walls in the back get some depth and actually look curvy with SSAO rather than like a flat distorted wall. The transition between the front truss and the wall aren't as harsh anymore either and their shape is defined a bit more, their metallic surface is shaded better and convey the depth better. Most people would call it "It looks less floaty" objects look more integrated into the scene rather than abstract floating objects painted on top. Ofcourse without shadows this effect is not complete, it would look a tad better with shadows.
How can i use it?
You can enable Screen Space Ambient Occlusion by opening 'Preferences' and selecting the 'Display' tab, here you'll find the 'Screen Space Ambient Occlusion' tab and its coresponding options.
What can i change?
Screen Space Ambient Occlusion comes with few but very important options. You can change the blur size (Blur Size), the strength/darkness/brightness (Effect), the radius (Scale), the max radius (Max Scale) and the distance inclusion (Factor). In addition to these options Screen Space Ambient Occlusion will also react to the Deferred Rendering option 'Light Softening' which can be found in the 'Deferred Rendering' section, it controls whether light (and thus SSAO) should be softened or not.
Caveats?
Screen Space Ambient Occlusion as the name implies is only used in Screen Space, objects outside your view are not included and thus not properly included when they stick into your screen partly, most noticeably SSAO will not correctly work at the edge of your screen, this is a limitation of SSAO but the price of a very cheap feature.
Screen Space Ambient Occlusion does not scale with resolution, this means that if you take snapshots at higher or lower resolution than your current window you'll have to reconfigure Screen Space Ambient Occlusion for these resolutions, Screen Space Ambient Occlusion shares this weird behavior with 'Light Softening', 'Screen Space Reflections' , 'Depth of Field' and 'Volumetric Lighting'. Keep this in mind.
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