Each mesh has properties that control how the Enlighten precompute treats it. We recommend that your editing tools assign appropriate defaults for these properties, and let the artist override them when necessary.

Radiosity: include or exclude

Each mesh may or may not be included in Enlighten radiosity computations. Excluded meshes have no effect on the indirect lighting result, but can still be lit by indirect lighting.

The meshes in the scene that have a fixed shape and position are static. The meshes that can move during gameplay are non-static.

Meshes that are static should be included by default. For example:

large architectural features such as terrain and buildings
smaller props such as furniture, debris or foliage

Meshes that are non-static should be excluded by default. For example:

objects that move around the world during gameplay
objects that deform during gameplay, such as skeletal meshes
objects that are destroyed or removed during gameplay.

If an object that is moved or removed during gameplay were included in Enlighten radiosity computations, the indirect lighting might look obviously incorrect.

Indirect lighting: lightmaps or probes

Each mesh can receive indirect lighting either from lightmaps or probes. Which method is best depends on the mesh.

When to use lightmaps

Lightmaps can only be used with meshes that are both static and rigid.

They provide a good balance between quality and cost for:

meshes with surface area (or groups of meshes with combined surface area) larger than the lightmap pixel size
meshes with simple topology easily unwrapped to a flat surface, such as terrain and buildings
meshes that can't be lit efficiently using probes

When to use probes

Probes can be used with any type of mesh, including:

static or rigid meshes
meshes that move or deform at runtime

They provide a balance between quality and cost for:

meshes that are relatively small, and so can be lit effectively using a limited number of samples per mesh
meshes with complex topology that isn't easily unwrapped to a flat surface, such as foliage or body parts

Material properties

By default, all indirect light that strikes a surface is diffusely reflected. For materials with translucency that doesn't change at runtime, you can specify the fraction of indirect light that passes through the surface.

By default, the precompute treats the back faces of meshes as invalid. To avoid unnecessary computation, radiosity isn't computed for surfaces that see invalid back-faces; these surfaces have invalid indirect lighting.

When a mesh is excluded from the radiosity computation, the back faces of adjacent meshes can be exposed. To prevent invalid lighting, check for invalid back faces visible through holes that may have been introduced when a mesh was excluded.

Two-sided surfaces might be used to represent thin objects. To prevent issues caused by invalid back faces, the artist can specify the way Enlighten treats the back faces of such meshes. For thin opaque objects such as sheets of metal, Enlighten can treat the back face as opaque. For objects that simulate cloth, such as curtains or flags, you can make both front and back faces diffusely transmit part of the incoming light.