Ambient occlusion is a graphics rendering technique that simulates the effects of ambient light on 3D objects. It involves darkening areas where light is blocked or reflected by other objects, creating soft shadows and realistic contrasts.

Ambient occlusion is important for the realism of 3D video games, as it adds depth and relief to the scene, taking into account the geometry and orientation of objects.

There are different types of ambient occlusion, which are based on different algorithms and parameters, offering more or less faithful and effective results.

Why is ambient occlusion important for 3D video games?

Ambient occlusion is important for 3D video games because it adds depth and dimension to the scene. It allows players to distinguish objects from one another based on their shape and orientation. It also makes colors appear more natural , preventing them from being too bright or too dark. Ambient occlusion therefore makes 3D video games more visually appealing and immersive .

What are the different types of ambient occlusion?

There are different types of ambient occlusion, each based on different methods and parameters. These types of ambient occlusion have complicated names, such as SSAO, HBAO, HDAO, or VXAO. But don't worry, we'll explain what they mean and how they work.

SSAO: Screen Space Ambient Occlusion

SSAO simplest and most common type of ambient occlusion . It's based on a simple idea: the closer two objects are to each other , the more shadows they cast on one another . SSAO therefore measures the distance between objects on the screen, using an image called the z-buffer .

The z-buffer is like a map that shows the distance between each point on the screen and the camera. Then, SSAO compares the distance between neighboring points to determine if they cast shadows. If so, it darkens the point according to the level of shadow.

• Advantages : It is quick and easy to do, it adapts to camera and object movements, and it works with all 3D games.
• Disadvantages : it doesn't take into account the direction or color of objects, it doesn't differentiate between near and far objects, and it doesn't handle edges or transparencies well. Therefore, it can create shadows that are too dark, too blurry, or poorly placed, which are not very realistic.

The HBAO: Horizon-Based Ambient Occlusion

HBAO is a more advanced type of ambient occlusion than SSAO . It is based on a more complex idea: the higher an object's horizon , the more ambient light it receives . An object's horizon is like its line of sight to the sky.

For example :

• If you are at the top of a mountain, you have a very high horizon, because you can see a lot of sky.
• If you are in a valley, you have a lower horizon because you see less sky.

The HBAO measures the horizon of each point on the screen using an image called the normal buffer . The normal buffer is like a map that shows the direction of the surface of each point . Then, the HBAO compares the horizon of neighboring points to determine if they cast shadows. If so, it darkens the point according to the level of shadow.

• Advantages : It is more precise and realistic than SSAO. It takes into account the direction and color of objects, differentiates between near and far objects, and handles edges and transparencies better. Therefore, it creates thinner, sharper, and better-placed shadows, enhancing the realism of the scene.
• Disadvantages : It is more expensive and complex than SSAO. It requires measuring the horizon of each point, which demands more resources. It also depends on the quality of the normal buffer, which can be inaccurate or noisy. It doesn't work with all 3D games; they must provide the normal buffer or use a compatible graphics engine.

HDAO: High Definition Ambient Occlusion

HDAO is a more effective type of ambient occlusion than HBAO . It is based on a more adaptive concept: the more samples a point needs , the greater its chances of being occluded by surrounding objects . The samples are like viewpoints taken around a point to see if it is illuminated or not.

For example :

• If you are in a dark room, you need a lot of samples to see if you are blocked by a piece of furniture or a wall.
• If you are in a bright room, you need fewer samples to see if you are occluded by a window or a lamp.

HDAO calculates the number of samples for each point on the screen , using a method that varies the number of samples based on the distance and angle of the points. Then, it compares the number of samples with neighboring points to determine if they cast shadows. If so, it darkens the point according to the level of shadow.

Advantages : It is high-quality and efficient. It uses an optimal number of samples for each point, which avoids loss of quality or wasted resources. This results in more detailed and deeper shadows, improving the overall quality of the scene.

Disadvantages : It's incompatible and difficult to configure. It doesn't work with all 3D games; they must use a specific graphics engine, such as AMD's or Ubisoft's. It also depends on the player's settings, who must choose the minimum and maximum number of samples, as well as the radius and intensity of the occlusion.

VXAO: Voxel Accelerated Ambient Occlusion

VXAO is a more advanced type of ambient occlusion than HDAO . It's based on a more comprehensive idea: the more accurate a point's voxelized representation of the scene , the more likely it is to be occluded by surrounding objects . The voxelized representation is like a 3D model that reproduces the scene with small cubes called voxels.

For example: if you have a house in voxels, you can see all the details of its structure and lighting.

The VXAO therefore creates a voxelized representation of the scene on the screen, using a method called voxel cone tracing . Voxel cone tracing is like sending virtual cones in all directions from each point to see which voxels are blocking the light.

Next, it compares the voxelized representation of neighboring points to determine if they cast shadows or not. If so, it darkens the point according to the level of shadow.

Advantages : It is detailed and deep. It uses a complete and accurate voxelized representation of the scene, which allows it to capture all possible occlusion effects, including those caused by moving objects or multiple light sources. It therefore creates very fine and deep shadows, which increase the depth of the scene.

Disadvantages : It's resource-intensive and limited. It requires creating a voxelized representation of the scene, which demands significant resources, particularly video memory. It's not compatible with all 3D games; they must use a specific graphics engine, such as Nvidia's or Square Enix's.

Ambient occlusion in current video games

Ambient occlusion is a graphics rendering technique used in many current video games. It enhances realism and player immersion by creating shadow and contrast effects that add depth and dimension to 3D scenes. Here are some examples of games that use ambient occlusion:

• Red Dead Redemption 2 : This open-world action-adventure game developed by Rockstar Games uses HDAO to create soft, realistic shadows in both natural and urban environments. The game also features a photo mode that allows players to capture images with various ambient occlusion settings.
• Metro Exodus : This first-person shooter developed by 4A Games uses VXAO to create subtle, deep shadows in post-apocalyptic environments. The game also employs a technique called Global Illumination , which combines ambient occlusion with light diffusion to create dynamic color and lighting effects.
• Assassin's Creed Valhalla : This open-world action RPG developed by Ubisoft uses HBAO+ to create crisp, precise shadows in historical and mythological environments. The game also uses a technique called Screen Space Reflections , which combines ambient occlusion with light reflection, to create realistic mirror and water effects.

To enable and adjust ambient occlusion in game graphics settings, you generally need to access the advanced options menu, where you can choose the type and intensity of ambient occlusion. You should also consider the effects of ambient occlusion on system performance and power consumption. Indeed, the higher the ambient occlusion, the more resources it demands from the graphics processing unit (GPU) and graphics card, which can lead to a decrease in frame rate or an increase in system temperature.

Ambient occlusion in the future of video games

Ambient occlusion is a graphics rendering technique that still has limitations and challenges. It depends on the quality and precision of the algorithms used, as well as the power and compatibility of the systems involved. Here are some possible ways to improve ambient occlusion:

The use of ray tracing

Ray tracing is a graphics rendering that simulates the path of light rays in a 3D scene , taking into account their interactions with objects and materials. Ray tracing allows for more realistic and precise calculation of ambient occlusion than current techniques, but it also requires significantly more resources.

Therefore, special graphics cards, such as those from Nvidia or AMD, which integrate units dedicated to ray tracing, must be used.

The use of artificial intelligence

Artificial intelligence is a technique that uses algorithms capable of learning and evolving based on the data provided. Artificial intelligence can therefore be used to optimize ambient occlusion calculations by adapting the number of samples or the occlusion radius according to the scene or movement.

It can also be used to correct artifacts or inaccuracies caused by current techniques, using neural networks or pre-trained models. But this use of artificial intelligence also raises social and economic questions. In France alone, the use of AI eliminates 217 jobs .

It can also be used to correct artifacts or inaccuracies caused by current techniques, using neural networks or pre-trained models.

The use of virtual reality

Virtual reality is a technique that immerses the player in a 3D environment using a headset or special glasses . Virtual reality can therefore benefit from ambient occlusion, which enhances the realism and depth of the scene.

However, it also presents challenges, such as the need for a high and consistent frame rate to avoid nausea or headaches. Therefore, ambient occlusion techniques adapted to virtual reality must be used, such as Foveated Rendering , which reduces the graphic quality of peripheral areas of the field of view.

The future prospects for ambient occlusion are therefore numerous and promising. It can contribute to creating more beautiful and realistic 3D video games, but it must also adapt to new technologies and the new demands of gamers.

FAQs

What is ambient light?

Ambient light is light that comes from all directions and illuminates the scene evenly. It does not have a specific source; it is the result of light being scattered by the atmosphere, clouds, walls, etc.

Ambient light is often used in video games to create basic lighting , which can then be supplemented by direct light sources, such as the sun, lamps, fires, etc.

What is the difference between ambient occlusion and cast shadows?

Cast shadows are the shadows cast by objects when illuminated by a direct light source. They depend on the object's position and shape, as well as the direction and distance of the light source. Cast shadows are often used in video games to create contrast and depth between objects and the background.

Ambient occlusion is the shadow cast by objects when illuminated by ambient light. It depends on the proximity and orientation of objects relative to each other, as well as the radius and intensity of the ambient light. Ambient occlusion is often used in video games to create realism and fine detail in objects.

How do I enable or disable ambient occlusion in a video game?

To enable or disable ambient occlusion in a video game, you usually need to access the game's graphics options menu , where you'll find a setting dedicated to ambient occlusion. This might be a simple on/off button, or a slider that allows you to choose the level of ambient occlusion.

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What is the impact of ambient occlusion on video game performance?

Ambient occlusion has an impact on video game performance, as it requires more calculations from the graphics processing unit ( GPU ) and graphics card.

The higher the level or type of ambient occlusion, the more resources it consumes . This can lead to a drop in frames per second (FPS), which measures the game's smoothness, or an increase in system temperature, which can cause overheating or slowdowns.

What is the benefit of ambient occlusion for the player?

The advantage of ambient occlusion for the player is that it makes the video game more beautiful and immersive . It allows for the creation of shadow and contrast effects that give relief and depth to 3D objects.

It also allows for more natural and harmonious colors. Ambient occlusion therefore contributes to creating a more realistic atmosphere and ambiance in video games.