Post Process Effects

Unreal Engine provides Post Process Effects to allow artists and designers to tweak the overall look and feel of the scene. Examples of elements and effects include bloom (HDR blooming effect on bright objects), ambient occlusion, and tone mapping.

Post Process Volume

The PostProcessVolume is a special type of volume that can be added to a level and, because Unreal Engine 4 does not make use of post processing chains, these volumes are currently the only way to manipulate post processing parameters. The new system is not complete and we will expose some programmability, but we want the common cases to be handled very well by the system. This makes it easier for artists/designers to use the system and for programmers to optimize it.

In Unreal Engine 4, each PostProcessVolume is essentially only a type of blend layer. Other blend layers might come from game code (e.g. hit effects), UI code (e.g. pause menu), the camera (e.g. vignette), or matinee (old film effect). Each layer can have a weight so it will be easy to blend effects.

Blending is always done with a lerp (linear interpolation) and only Enabled volumes are getting blended. A PostProcessVolume will only be applied when the camera is within the bounds of the volume unless the Unbound property is checked.

The properties found in the PostProcessVolume are explained below:

Property Description
Settings The Post Process Settings for the volume. The checkbox in front of most properties defines if the line in the volume is blended using the Blend Weight of the volume.
Priority Defines the order in which multiple volumes are blended together. The volume with the highest priority takes precedence over all other overlapping volumes.
Blend Radius Distance in Unreal units around the volume at which blending with the volume's settings occurs.
Blend Weight The amount of influence the volume's properties have. 0 is no effect; 1 is full effect.
Enabled Whether the volume affects the post processing or not. If true, the volume's settings will be used for blending.
Unbound Whether the bounds of the volume are taken into account. If true, the volume affects the entire world, regardless of its bounds. If false, the volume only has effect within its bounds.

Post Process Settings

The post process settings are all of the properties of the various post process effects that can be controlled or overridden. These properties are declared in the UScene class. The PostProcessVolume contains an FPostProcessSettings struct as its Settings property that contains all of these properties and allows them to be overridden by the volume.

For descriptions of each of the available settings, see the page for the corresponding effect below.