| sc94597 said: Technically there is still ray-tracing in Software Lumen, it's just the rays are traced against Signed-Distance-Fields, which are approximate volumetric representations of the scene geometry. That's why it is less accurate. Hardware lumen works against actual scene geometry (or a very close representation of it, i.e Nanite fallback meshes) because it has available the specialized hardware to accelerate it for real-time workloads.
Example of an SDF from Wikipedia. The difference is primarily the data structures/geometric representation being traced against. In Software Lumen you have the SDF representation, while in Hardware Lumen there is the TLAS/BLAS BVH. |
Yeah, I didn't want to go into details there, point being that although SW Lumen gives RT alike results, it's quite simplified and prone to mistakes with quite a bit less details than "standard" RT. SW Lumen is fairly fast and often good enough though, and if games are actually made with only that in mind from the start, those problems can be mitigated to a degree.
