What Is Ambient Occlusion and How Is It Used?

What is ambient occlusion? If you’re a PC gamer, there is a long list of acronyms and jargon names you’ll have to keep in mind when tweaking your graphics settings. It can get somewhat daunting to understand what each of the settings does, especially if you’re new to graphical tweaking as a whole.

Now, ambient occlusion (AO) as a whole doesn’t have a major impact on the clarity or fidelity of character models. Instead, it serves more as a major step toward immersion, enhancing lighting and the like. So, this guide will serve as a deeper dive into how ambient occlusion works and which types might work best for your favorite games.

Defining Ambient Occlusion

So, before diving into the deep end, let’s define what ambient occlusion actually is. If you’re familiar with photography, ambient occlusion refers to lighting and shadows. It isn’t dynamic lighting, but it is directly affected by lights within a scene. The technology as a whole helps to provide realism to a given object or scene in a game.

You’ll see it with the various higher-end graphics options, but it doesn’t truly use a ton of processing power to get its point across.

Where It’s Used

Ambient occlusion is almost exclusively used as a way to increase graphical immersion. You’ll see it alongside things like dynamic shadows and independent lighting sources in most games. Some games come with the option to select multiple different types of ambient occlusion, which will be explored further in depth.

How It Works

Rather than working as a result of dynamic lighting, ambient occlusion is the result of fake lighting sources baked into objects and geometry in any given game scene. The various nooks and crannies on a game model cast simulated rays of light that then cast individual shadows over parts of the geometry.

Think of looking at any given person’s face. You’d expect some shadowing, especially during certain hours of the day. That same basic principle of physics is applied to game models and objects on the terrain, which helps greatly when looking approaching immersion.

The Different Types of Ambient Occlusion

There are four different types of ambient occlusion, with two of them being fairly closely related. As such, we’ll count those two as the same one when discussing the techniques and how they work.

SSAO

SSAO or screen space ambient occlusion, is graphical sleight of hand. Instead of using punishing visual settings which can greatly tax a computer, it instead focuses solely on what you can see. SSAO as a whole is great when engineering games for lower-spec machines, as you’ll often see it used in retro-inspired titles to simulate some of the various techniques used by software rendering.

SSAO isn’t truly ambient occlusion in the strictest sense, instead, this implementation is messing with the pixel depth of everything on screen. This is the lightest of all ambient occlusion techniques to use, requiring very little in terms of overall hardware from a gamer.

HBAO and HDAO

HBAO and HDAO are essentially the same, just packaged by different GPU manufacturers. If you’re up to date with NVIDIA or AMD, you know each has its own proprietary tech. You’ll see this with things like AMD’s FSR or NVIDIA’s DLSS. That said, HBAO and HDAO are along the same lines.

HBAO is short for horizon-based ambient occlusion, while HDAO is high-definition ambient occlusion. The overall technology is pretty much identical, hence why we’ve grouped them together. This is where you can definitely start feeling a bit of a squeeze when it comes to your graphics hardware.

What makes this such an effective method of ambient occlusion is how it approaches rendering. It takes samples from different areas and then renders them in full resolution, even for small objects like stair steps or bookshelves. HBAO can be more taxing on hardware but can look absolutely stunning in motion. It really does make a difference if you’ve got the components to enable it.

VXAO

VXAO is short for voxel accelerated ambient occlusion. This is the heavy hitter when it comes to absolute graphical fidelity. VXAO isn’t just rendering what’s on the screen or in a particular scene, but everything. You’ll see it in use with real stunners as far as games go, with one breathtaking implementation being done in Crystal Dynamic’s Rise of the Tomb Raider.

This is a fairly taxing technique, so it isn’t well suited for some games. First-person shooters and the like won’t benefit from VXAO, as your viewpoint is so limited. Third-person action titles, RPGs, and exploration games certainly benefit from it, however.

VXAO is still a fairly new technology when it comes to ambient occlusion implementation. The coming years will really prove its mettle in terms of how it’s utilized. Needless to say, it should yield some absolutely stunning results with more powerful graphics hardware on consoles and PCs.

The Pros and Cons of Each Type

As you can imagine, there are pros and cons to each type of ambient occlusion. Let’s explore those a little more in-depth so you can make an informed decision when tweaking your favorite games.

SSAO

Pros

• Less resource intensive than other options.
• Highly efficient while not sacrificing visual fidelity.
• It is the easiest option to optimize for older or lower-spec computers and consoles.

Cons

• More graphically demanding games can actually look worse with SSAO.
• While being less intensive, it isn’t true ambient occlusion.

HBAO and HDAO

Pros

• Has better overall visual clarity and immersion than SSAO.
• Can usually have optimized modes intended for your GPU, whether it is AMD or NVIDIA.
• It can work in conjunction with acceleration tech like FSR or DLSS.

Cons

• It has a higher overall resource requirement than SSAO.
• HBAO and HDAO are firmly mid-range solutions and might impede visual fidelity on some resource-intensive games.
• You’ll likely have to tweak games on a per-case basis to get the best visual results.

VXAO

Pros

• VXAO looks absolutely stunning.
• Offers the most life-like effect on ambient lighting for any game.
• It is likely going to set the new standard for ambient occlusion in games over the next decade.

Cons

• It is highly taxing on any system.
• VXAO might not be the best fit for every game, like resource-intensive first-person shooters.
• This method might run quite poorly on low to mid-range hardware.

Is Ambient Occlusion Important to Modern Computing?

So, with everything you’ve read, do you think AO is an important piece of tech in modern gaming? There is something to be said about the push for graphic fidelity over the last two decades. Games have started becoming better and better looking, with visual fidelity on par with some of the top cinematic experiences you might see in theaters.

However, that visual fidelity can come at a heavier cost than you might think. While ambient occlusion might not seem like an absolutely vital option, especially if you’re into competitive gaming, it is just a bit of icing on the cake for visual options.

As such, it might not be important to every user. Those who are building absolutely monstrous high-end gaming PCs will likely enjoy turning on all the bells and whistles when running games that serve as benchmarks for the foreseeable future. AO has its place, even if it’s something that might be taken for granted.

The image featured at the top of this post is ©antoniodiaz/Shutterstock.com.