What does SSAO (Screen Space Ambient Occlusion) mean? answered

Whether you’re a console or PC gamer, you’ve probably heard of ambient occlusion in screen space. This is doubly true for PC gamers as they play around with graphics settings for optimal performance on a particular rig. The problem is that not every game describes exactly what SSAO does. Our guide explains ambient occlusion in screen space and how it affects visual fidelity.

What does SSAO do?

Basically, screen-space ambient occlusion adds ambient shading, or shadow pockets, to various objects that are at rest in a game scene. Ambient lighting or shading refers to any indirect or natural lighting affecting a scene. Imagine the dark spots in the folds of a bed sheet or the shadow under a water bottle. You might even notice a subtle shadow under your TV stand.

These finer elements of lighting can be handled in a variety of ways. Since the advent of RTX-enabled GPUs and the PS5 and Xbox Series X/S, some games have used ray tracing to simulate environmental shading. However, screen-space ambient occlusion uses screen-space information to determine how ambient shading is distributed across a scene.

That has its limits. Anything that is not in the camera’s field of view is not taken into account in this lighting approach. Record any game with SSAO and slowly pan the camera until an object with ambient shading is just out of view. You may notice the shadows fading in and out as more of that object becomes visible to the player. This is the Ambient Occlusion screenspace element in screenspace.

Where did SSAO start?

The original Crysis from 2007 pioneered the above environment. It is the first commercially released video game to take advantage of screen space ambient occlusion. While Crysis was an extremely demanding PC title, SSAO would make its way to consoles soon after. Rudimentary implementations were seen back in 2008 with games like Gears of War 2.

While quality varied from title to title, ambient occlusion in screen space became more common as the PS3 and Xbox 360 generations progressed. It is still used in many triple-A titles to this day, including Resident Evil Village on last-gen consoles and the non-ray-traced modes of current-gen consoles.