Sun Shafts
Screen Space Ambient Occlusion

Screen Space Ambient Obscurance

This image effect approximates Ambient Occlusion in realtime, as an image post-processing effect. It darkens creases, holes and surfaces that are close to each other. In real life, such areas tend to block out or occlude ambient light, hence they appear darker. It is an improvement to the existing Screen Space Ambient Occlusion effect in terms of quality and – depending on settings and hardware – speed. Additionally, it doesn’t rely on a generated normals buffer as it is recreating them on the fly based on depth.

As with the other image effects, you must have the Standard Assets Effects package installed before it becomes available.

The following two screenshots compare the results of a simple scene employing this occlusion effect.

The high degree of ambient lighting basically removes all shading which makes objects hard to decipher.
The high degree of ambient lighting basically removes all shading which makes objects hard to decipher.
With added ambient occlusion, the resulting shading makes objects visible.
With added ambient occlusion, the resulting shading makes objects visible.

The degree of darkening (in short: AO) is mostly controlled through the Intensity and Radius parameters. However, there is a post blur step performed to soften out the raw and noisy AO results. The following screenshot shows a result that performs a smaller blur.

Frequency and strength of the occlusion can be controlled through the post blur step (Blur Iterations and Blur Filter Distance)
Frequency and strength of the occlusion can be controlled through the post blur step (Blur Iterations and Blur Filter Distance)

Properties

Property: Function:
Intensity The degree of darkness produced by the effect.
Radius The maximum area taken into account when checking for possible occlusion.
Blur Iterations The blur passes to soften out the naturally noisy result.
Blur Filter Distance The sample distance used during the blur passes.
Downsampling The resolution at which calculations should be performed. Downsampling increases rendering speed at the cost of quality.

Hardware Support

This effect requires a graphics card that supports Shader Model 3 and depth textures. See the Graphics Hardware Capabilities and Emulation page for further details and a list of compliant hardware.

Sun Shafts
Screen Space Ambient Occlusion