Changes in 3.12.P1 (UE4.26.0)

Enlighten texture updates take significantly less time on PS5 and Xbox Series X.
Significantly increased responsiveness of probe visualisation in a world which contains many probes.
Reduced Enlighten Probe Memory stat when probe lit objects and adaptive probe volumes exist within many different streaming levels.
Enlighten Probe visualisation spheres far from the camera now appear larger to ensure they are clearly visible.
The editor now reports a warning in the Enlighten Errors window after the precompute for each mesh that was used for radiosity and has a large number of small triangles relative to the cluster size.

Fixed precompute error for level that was originally created in UE4 without Enlighten.
Fixed an intermittent crash that could occur during the precompute when a mesh has an extremely large cluster size.
Fixed a use after free crash that could occur when a streaming level is loaded and immediately unloaded.
Fixed precompute warnings incorrectly reported as errors when using SNDBS2 distributor.
Fixed incorrect Enlighten indirect lighting for Sky Atmosphere in a level which contains a Scene Capture 2D.
Fixed slow save for a level which contains a large number of foliage instances and was saved many times.
D3D12: Fixed bright flash visible in Enlighten reflections when indirect lighting is changing.
Fixed unintended modification of the level package by the Enlighten precompute commandlet when level contains UChildActorComponent and Enlighten data is stored in a separate asset.
Fixed missing or incorrectly placed probes when the probe regions within a single zone cover an extremely large volume of space.
Fixed division by zero exception in per pixel probe lighting runtime update.
Fixed missing link to actor related to lightmap UV packing warnings in Enlighten Errors window.

Changes in 3.12.R (UE4.26.0)

Use automatic probe placement and per pixel probe lighting at scale in a massive world:

Efficiently light large open spaces with additional probe placement resolution options: 1/32, 1/64, 1/128, 1/256.
Significantly reduced precompute time for automatic probe placement in a world with many probes across a large volume of space.
Significantly reduced update time and memory use for per pixel probe lighting in a world with many probes across a large volume of space.

Early Access: Enlighten indirect lighting in combination with real time ray tracing:

Enlighten indirect lighting contributes to ray traced global illumination.
Enlighten indirect lighting visible in ray traced reflections.
Ray traced occlusion of Enlighten indirect lighting for Spot, Point and Directional light actors.

The precompute time is now significantly reduced in a scene where automatic probe placement regions cover a large volume of space.
The precompute now uses Intel Embree library version 3.11.0 to take advantage of recent performance improvements.
Source control operations can now be used safely with assets that contain Enlighten data. Sync and revert operations are disabled when the level is currently loaded in the editor.

If you rebuild Enlighten libraries from source with Visual Studio 2017, it is no longer necessary to install the Visual Studio 2015 C++ build tools.
If you rebuild Enlighten libraries from source, the required Enlighten configurations are now automatically detected when you run GenerateProjectFiles.bat.

Fixed meshes with negative scale shown incorrectly with orange front faces in the Radiosity Back-faces visualisation.
Fixed missing indirect lighting for Rect light on some platforms when Barn Door Angle is below 88 degrees.
Fixed intermittent precompute failure when Windows regional format set to a language other than English, Japanese or Chinese.
Fixed a crash when per pixel probe lighting is enabled and probes are placed very far from the origin.
Fixed a crash after the precompute when the world contains two identically named levels.
Fixed a crash when the world contains two identically named levels precomputed separately.
Fixed a warning "Duplicated Enlighten ID" and incorrect lighting in a level which contains more than one actor based on the same static mesh blueprint.
Fixed a warning "failed to resolve archetype object" during hot reload of a class derived from UPrimitiveComponent.
Fixed a precompute error for a level which contains an Enlighten reflection capture actor and has Disable Enlighten checked.