What Is Ambient Occlusion? (SSAO, HBAO, HDAO And VXAO)

The gaming industry is thriving thanks to the technological advancements in hardware. This especially applies when it comes to processing power and graphics.

With new generation graphics cards, many gaming companies compete on delivering as realistic ambient lighting as possible.

Gamers know that there are a lot of graphics settings they can play with to make the game visually appealing.

Ambient occlusion is one of the settings that can help make a game more lively and dynamic.

So, what is ambient occlusion?

This guide provides an overview of this setting and details different types of it.

Table of ContentsShow

What Is Ambient Occlusion?

What Is Ambient Occlusion
The left side has ambient occlusion enabled, while the right side has it disabled. Can you see the difference?

Ambient occlusion is a rendering method that provides an approximation of how bright the light should be at different parts of the visible surface. It takes different factors into account, such as the environment in the game and the position of the light source.

It provides a realistic simulation of the shadowing objects that block the ambient light from different sources. With that in mind, ambient occlusion adds realism to 3D video games, mimicking light distribution in reality.

The first time ambient occlusion was mentioned was in 2001. Pearl Harbor with Ben Affleck was the first movie that introduced it, and although it wasn’t a masterpiece, it helped paw the way for gaming graphics to rise.

Ambient occlusion in the gaming industry was first introduced in 2007. Game development company Crytek introduced it in Crysis. The game earned a lot of accolades, and the company sold over 3 million copies of the game.

However, given that the shadowing was too graphically demanding for many gaming machines in the 2000s, a lot of gamers couldn’t benefit from this feature until much later. Nevertheless, a lot of gamers enjoyed the realistic pinch that the game had to offer.

Ambient occlusion has improved over time, so there are different types of it, which are described below.

Types Of Ambient Occlusion

The Witcher 3 Ambient Occlusion None
The Witcher 3 without ambient occlusion enabled

Different graphics cards, their architectures, and rendering technologies contributed to various ambient occlusion enhancements, so there are different types prominent in today’s titles.

Some of the most commonly found settings include SSAO, HBAO, HDAO, and VXAO.

SSAO

The Witcher 3 Ambient Occlusion SSAO
The Witcher 3 with SSAO enabled

SSAO or Screen-Space Ambient Occlusion was the type of occlusion introduced by Crytek when debuting Crysis. However, to save the processing power, SSAO doesn’t consider the space and elements that produce shadows. Instead, SSAO looks at the pixels around the element and their depth. This approach made CPU usage more efficient while introducing a dynamic rendering to make the ambient more realistic.

That said, SSAO, instead of focusing on the entire screen, measures ambient occlusion in pixel depth at a part of the screen. Still, that came with some drawbacks such as noise and at times, inaccurate shadow distribution if the pixels weren’t measured properly.

It’s also worth mentioning that SSAO didn’t have loading times, which made games run smoother. However, graphics card performance and video game demands have increased over time, which brought in new techniques.

HBAO

The Witcher 3 Ambient Occlusion HBAO+
The Witcher 3 with HBAO+ enabled

HBAO, also known as Horizon Based Ambient Occlusion, was the next enhancement in graphic rendering techniques.

It’s an approach that Nvidia introduced to address the grain and noise that came with pixel depth measurements of SSAO. It considers the ambient and the environment instead of just the pixels.

With the help of geometry, it is much more effective at rendering shadows and lighting. The major disadvantage of HBAO is that, unlike SSAO, it requires more processing power in both CPU and GPU.

Later on, HBAO+ was featured to provide a less performance-tasking algorithm of light and shadow sampling.

HDAO

What Is HDAO Ambient Occlusion

HDAO or High Definition Ambient Occlusion is a similar technique, although it is meant for AMD graphics cards to compete with Nvidia’s HBAO.

There’s no difference between HBAO and HDAO, except that they’re native to their distributer’s GPU.

VXAO

What Is VXAO Ambient Occlusion

VXAO, namely Voxel Ambient Occlusion, is the closest video games can get to reality in terms of lighting and shadow rendering. However, not many games boast this setting, mainly because it’s too tasking and will push the limits of your processor and graphics. It also has a different approach than SSAO and other techniques.

In simple words, VXAO will render geometrical objects and approximate the shadowing, outside the scene that you’re experiencing. This approach gives scenes even more realistic touch, providing a great comparison between modern-day games and what video games used to look like in the past.

In more technical words, VXAO converts pixelated objects on the screens into voxels, which are 3D, cube-shaped pixels. Hence, the voxel ambient occlusion. As a result of their 3D structure, voxels can estimate the dimensions of certain geometrical objects inside games and result in precise and sleek light and shadow rendering.

Ambient Occlusion vs. Ray Tracing

Ambient Occlusion vs Ray Tracing

SSAO focuses on pixel-depth and doesn’t take shapes and objects into account, leading to darkened corners, grain, and inaccurate shadows.

On the other hand, Ray Tracing as a novel technology focuses on more factors like the geometry of different shapes and objects, surfaces, and light to render accurate and realistic shadows.

It’s also a step forward from HBAO and HDAO that focus purely on geometry. Additionally, Ray Tracing processes and renders only what’s visible to the player. In other words, the approximation of lighting and shadows is only performed on the camera view field.

Currently, there are not too many gamers that can run Ray Tracing, mostly because the feature is native to RTX cards, and only a handful of games support this next-generation feature. However, as the gaming industry is progressing and the new generation of RTX graphics is on its way, more games will support this technology.

Conclusion

Ambient occlusion is a method that calculates and approximates the right brightness in the in-game ambient and brings players closer to the digital world. Different types of ambient occlusion developed throughout the years together with new graphics.

While more occlusion methods such as Ray Tracing will inevitably emerge, it’s important to note that ambient occlusion isn’t the only way to enhance the look of your game and make it closer to reality.

Still, it’s a complex yet fascinating technique that makes both games and movies more dynamic.

Danica Simic
Danica Simic

Danica is a software engineer and aspiring data scientist. She developed a vast passion for writing ever since childhood that she now uses to produce content about the latest tech, games, and gizmos. Other than that, she’s also a swimming enthusiast and in her spare time, she writes fantasy stories and draws.