Tim Hobson

How to use Distance Field Ambient Occlusion

In this How-to we will cover how to setup and use dynamic Distance Field Ambient Occlusion (DFAO) with Mesh Distance Fields enabled. This page will cover the various settings that can be adjusted in the Sky Light to affect the look and feel of DFAO in your scene.

how to Enable DFAO

1. Start by navigating to the Modes panel, then in the Lights section, click on the Sky Light and then drag it into the Viewport.
2. With the Sky Light selected, look at its properties in the Details panel. In the Transform section set the Mobility to Movable.
3. ‚ÄčAt this point Distance Field Ambient Occlusion will be enabled for your scene. Use the settings below to adjust its properties in the Sky Light and use the visualization view mode to see DFAO own its own in your scene.

Visualization of dfao

To visualize Distance Field AO in your scene you can go to the Viewport Show Visualize Distance Field Ambient Occlusion.
 

setting in the skylight actor

‚ÄčThis part of the How-to will look at what each property in the Sky Light Actor can do to affect how Distance Field Ambient Occlusion is used when enabled.

Properties

The settings for DFAO are located in the Details panel under the Distance Field Ambient Occlusion tab when the Sky Light actor is selected.
Properties Description
Max Occlusion Distance Max Distance that the occlusion of one point will affect another. Higher values increase the cost of Distance Field AO exponentially.
Contrast Contrast S-curve applied to the computed AO. A value of 0 means no contrast increase, 1 is a significant contrast increase.
Min Occlusion Controls the darkest that a fully occluded area can get.
Occlusion Tint Tint color on occluded areas, artistic control.

Occlusion Max Distance

The setting for Occlusion Max Distance is the amount of distance between one point of occlusion on an object that will affect another point of occlusion on another object. When you use higher values this will increase the distance that occlusion affects which in-turn will increase the cost of using DFAO exponentially.

Contrast

The setting for Contrast will adjust the contrast of the DFAO when using the slider. The values are clamped to be between 0 to 1, so using a value of 0 will apply no contrast to the ambient occlusion where as using a value of 1 will be a significant increase in contrast.

Min Occlusion

The setting for Min Occlusion will adjust how dark any fully occluded area can get. Using the default value of 0 will disable this feature, while using a value of 1 will reduce the darkness of the occlusion.

Occlusion Tint

The setting for Occlusion Tint will provide the most artistic control over your ambient occlusion. Any occluded areas that is using Distance Fields can have the occlusions color adjusted to fit your scene.

Conclusion

By using Distance Field Ambient Occlusion in your game you can get a much more natural and realistic sense of the objects being grounded in your scenes that are dynamically lit. Using the properties in the Sky Light Actor you have full artistic control to tweak how the ambient occlusion in your scenes will look and feel to bring them to life.