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Post Process Effects

Effects applied to the whole rendered scene prior to being rendered.

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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.

Physically-Based Post Process

As of Unreal Engine 4.15, the filmic tone mapper has been enabled by default matching the standards set by the Academy Color Encoding System (ACES) . This enables the tone mapper in UE4 to easily target multiple display types, including High Dynamic Range (HDR) displays. The move to the ACES standard ensures consistent color is preserved across multiple formats and displays, while also as a way to future proof the source material used without having to adjust it for another medium.

The filmic tone mapper provides these added benefits:

  • Matches the ACES standard for Television and Film.

  • Additional Color Grading and White Balance control.

  • Emissive colors bloom in a more physically correct way now.

The new filmic tone mapper will look different than the tone mapper in previous versions of UE4 for content you may have developed. To use the older tone mapper you can enter the following console command: 

r.TonemapperFilm 0

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 an 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.

Effects

AntiAliasing_Topic.png

Anti-Aliasing

Smoothing of jagged edges using the FXAA method.

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Auto Exposure (Eye Adaptation)

Automatic adjustment of scene exposure to simulate eye adaptation from changes in brightness

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Bloom

Haloing to produce glow effects for bright objects such as lights.

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Blendables

Blendables assets can be smoothly interpolated and used to affecting the rendering (e.g. post processing, fog, Ambient Cubemap, ambient occlusion).

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Color Grading and Filmic Tonemapper

Tonemapping and color correction effects for adjusting scene colors.

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Depth of Field

Simulating focus by blurring the scene depending on depth.

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Lens Flare

Simulating scattered light from bright objects due to imperfections in camera lenses.

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Panini Projection

3D projection that fixes the perspective projection's geometric distortion on sides of the view having a wide FOV.

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Post Process Materials

How to author and blend custom Post Process passes with the Material Editor.

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Scene Fringe (Chromatic Aberration)

Chromatic aberration effect that simulates the color shifts near the edges of real-world camera lenses.

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Screen Space Reflections

Effect which alters the reflection that appear on the surface of materials within scene view.

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Vignette

Effect causing the brightness of the to decrease as the distance from the viewport's center increases.

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Using Lookup Tables (LUTs) for Color Grading

How to create and use your own lookup tables for color grading in Unreal Engine 4.

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