Lumen traces rays against a scene representation consisting of signed distance fields, voxels and height fields.
Daniel Wright, Technical Director of Graphics at Epic, said: Lumen uses ray tracing to solve indirect lighting, but not triangle ray tracing.
Unreal Engine 5 Demo Dreams Recreation New Video Focuses On The Making of the Soldier Figure Starting with Lumen, the new real-time Global Illumination system, many (including myself) wondered why there was no mention of ray tracing technology at work.
Luckily, instead of continuing to guess, we did learn a bit more straight from Epic in a follow-up interview with Eurogamer's Digital Foundry on the two main new Unreal Engine 5 features showcased on that demo: Lumen and Nanite.
According to Senior Graphics Programmer Brian Karis, Epic used PlayStation 5's primitive shaders (properly introduced by AMD with the RDNA 1.0 architecture), though the developers also made 'hyper-optimised' software shaders.