With Enlighten, the color of light reflected by a surface depends on its albedo (also known as base color). The color and amount of light emitted by a surface depends on its emissive color and intensity. You can change the albedo and emissive colors in-game using Blueprints.

By default, all indirect light that strikes a surface is reflected. For each material, you can specify the fraction of indirect light that passes through.

By default, the precompute treats the backfaces of meshes as invalid. To avoid unnecessary computation, radiosity isn't computed for surfaces that see invalid backfaces; these surfaces have invalid indirect lighting. When a mesh is excluded from the radiosity computation, the backfaces of adjacent meshes can be exposed. To prevent invalid lighting, check for invalid backfaces visible through holes that may have been introduced when a mesh was excluded.

You might use surfaces with a two-sided material (UE4 Documentation) to represent thin objects. To prevent problems caused by invalid backfaces, you can specify how Enlighten treats the backfaces of such meshes. For thin opaque objects such as sheets of metal, you can have Enlighten treat the backface as opaque. For objects that simulate cloth, such as curtains or flags, you can make both front and backfaces transmit part of the incoming light.

Albedo and emissive colors

By default, Enlighten automatically determines the surface albedo and emissive color at a given point on the surface by evaluating the material's base color and emissive outputs. This is known as static albedo/emissive because it works with material outputs that don't change in the game. There's no effect on indirect lighting when the color of a material using static albedo/emissive changes in game mode.

To animate the colors in game mode using blueprints, use the dynamic albedo/emissive material properties.

You can set albedo properties without affecting the emissive properties and vice versa. For example, a material can use static albedo and dynamic emissive at the same time.

You can also override these properties for a material instance in the Material Instance Editor.

Control the albedo color

In the Material Editor, set the Static Albedo Boost factor. This is applied to to the albedo color. The result can never be brighter than 100% white.

Use dynamic albedo

To force the material to use dynamic (single-color) albedo, as opposed to static (sampled) albedo:

In the Material Editor, under Enlighten, enable Use Dynamic Enlighten Albedo.
Expand Dynamic Enlighten Albedo.
Use the RGBA fields to specify the albedo color.

Changes to the Use Dynamic Enlighten Albedo property don't take effect until you run the precompute.

Control the emissive color

By default, materials don't emit light, even when they have emissive outputs. To make the material emit light, enable Use Static Enlighten Emissive. The Static Emissive Boost factor is applied to the emissive color when Use Static Enlighten Emissive is enabled.

Enable Use Dynamic Enlighten Emissive to force the material to use dynamic (single color) emissive, as opposed to static (sampled) emissive. This enables the Dynamic Enlighten Emissive fields, which determine the emissive color to use.

A change to the Use Dynamic Enlighten Emissive property does not take effect until after you run the precompute.

Disable automatic albedo updates

By default, static albedo/emissive is updated automatically when you make changes in the editor. To work around rare cases where the update of static albedo/emissive takes too long, you can disable automatic updates using Edit > Editor Preferences > Plugins > Enlighten > Disable Automatic Enlighten Static Albedo Updates. When checked, static albedo and emissive are still updated automatically when you:

play the level
save a sublevel
run the precompute
click Build > Update Enlighten Static Albedo

When automatic updates are disabled, static albedo and emissive aren't updated when materials are modified, which can produce incorrect lighting. We recommend leaving automatic updates enabled.

Backface type and indirect opacity

You can control how surfaces interact with indirect light with the following material properties. Backface Type determines the way Enlighten interprets the backfaces of these surfaces. Indirect Opacity determines how much indirect light is reflected by the surface; the rest passes through.

Your changes to these properties don't take effect until you run the precompute.

When Backface Type is Automatic, the backface type is determined automatically based on the material's Blend Mode and Two Sided properties.

The other values cause Enlighten to interpret backfaces as follows:

Invalid: indirect lighting is invalidated for any surface that can "see" the backface. Automatically chosen if the material is opaque.
Black: the backface absorbs all incoming indirect light. Automatically chosen if the material is two-sided and opaque.
Transparent: the backface is transparent to incoming indirect light. Automatically chosen if the material is not opaque.
Double Sided: both the frontface and backface diffusely transmit 50% of incoming indirect light, and diffusely reflect 50% of incoming indirect light. Automatically chosen if the material is two-sided and not opaque.

Indirect Opacity is ignored if Backface Type is Invalid or Black. Otherwise, the value of Indirect Opacity controls the amount of indirect light reflected by a surface using the material. A value of zero means all indirect light passes through the surface.

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