UE4 RnD – Light

Hi everyone as a part of my final project I have had to do a ton of UE4 research and after a month of digging around various systems, manually editing render settings and writing custom shaders I have now created this new category where I can share some of my world changing findings with you!

To start us off I would like to talk a bit about lighting in UE4. As advanced as UE4’s lighting system is, it has taken a few steps back since the engine’s release, the most notable side is that the engine does not (really) support real time global illumination – don’t get me wrong all lighting effects CAN be recreated, but they just require a little more manual work than advertised.
As such UE4’s currently lighting system relies on pre-computed lighting texture that goes over the entire level which is responsible for shading, color bleeding and reflection effects… this technique allows for an extremely detailed and complex lighting set ups to be played out on systems with older hardware – it’s a great solution!

However since this system is close to what offline renders like Keyshot do, I wanted to push it a little further to the point where I can get quality lighting that is on par with offline renderers.
An excellent starting point for this was the ArchViz community which works the UE4 to bring real time renders of architectural projects. After looking at the methods employed by Unreal forums user Koola and architect Fabrice Bourrelly I have arrived at this method.

To increase graphical fidelity I have taken to editing the Lightmass.ini file in the config folder for the project. As such my current setting for Production Quality Static Lighting is this:


Here is a comparison of the changes:

LIght Res

Untextured Version:

Test LIght v2

Conclusion – increasing the photon and light bounce numbers results in improved shadows and global illumination on par with offline renderers. This does dramatically increase lighting build time, but its is a one off process and as such does not a significant negative impact on workflow.


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