UE4 Indirect Lighting Cache

cafe; Well the only other thing I found in the map that might be weird, or at least that I’ve never seen before, is something called a characterindirectdetail volume. No idea what that does, but I have never seen one before. Everything else seems pretty standard. Maybe tonight I’ll cook a version without those volumes and see if it changes anything.

Lets nerd it up a bit.

Firstly: UE4 Indirect Lighting Cache

Epic Docs

Players are lit using the indirect lighting cache. You get an idea of how this would work simply by looking at the pictures with the samples shown on that page. Found this looking for solutions to player visibility (eg – what if these could be inverted so players are always the opposite of their intended lit value?) but beyond a basic understand of its existence I have no idea how you could modify it. These indirect lighting samples are generated close together at ground level and futher apart above the ground, see the image below for blank. Stands to reason as players in the air will be falling quickly and as such less “precision” required because light changes will be less obvious at speed. r.Cache.DrawLightingSamples 1 in the editor console (~) turns these on.

indirect lighting cache

Lightmass Character Indirect Detail Volume

This appears to generates samples above the ground rather than just on the surface. The docs say this would be used in a lift. The assumption here is that the indirect lighting cache generates a sample on the ground, however the vertical granularity is too low for a player moving up slowly on a lift. So if a lift was dark at the bottom but bright at the top the player may end up being “lit” using the dark value from the bottom, as there is no “floor” at the top of the lift for the engine to generate a value from. Epic Docs

The gif below shows how this affects the lift on ctf-blank.

character indirect detail volume


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