Pemalite said:
The demo is using Ray Tracing. It's what Global Illumination is. |
What I got from the tech interview is that they're using a lot of different techniques to work smarter rather than brute force it with hardware
https://www.eurogamer.net/articles/digitalfoundry-2020-unreal-engine-5-playstation-5-tech-demo-analysis
For example:
For shadows:
In lieu of triangle-based hardware-accelerated ray tracing, the UE5 demo on PlayStation 5 utilises screen-space as seen in current generation games to cover small details, which are then combined with a virtualised shadow map.
For light:
"Lumen uses ray tracing to solve indirect lighting, but not triangle ray tracing," explains Daniel Wright, technical director of graphics at Epic. "Lumen traces rays against a scene representation consisting of signed distance fields, voxels and height fields. As a result, it requires no special ray tracing hardware."
To achieve fully dynamic real-time GI, Lumen has a specific hierarchy. "Lumen uses a combination of different techniques to efficiently trace rays," continues Wright. "Screen-space traces handle tiny details, mesh signed distance field traces handle medium-scale light transfer and voxel traces handle large scale light transfer."
Dunno what they do about reflections, were there any in the demo?
Also for processing geometry, back to software instead of using hardware mesh shaders
"The vast majority of triangles are software rasterised using hyper-optimised compute shaders specifically designed for the advantages we can exploit," explains Brian Karis. "As a result, we've been able to leave hardware rasterisers in the dust at this specific task. Software rasterisation is a core component of Nanite that allows it to achieve what it does. (We can't beat hardware rasterisers in all cases though so we'll use hardware when we've determined it's the faster path.)
This is always a problem with hardware added for specific tasks. Better, smarter ways to handle things usually happen right along. It looks like the next Unreal engine will have all bases covered. (Apart from reflections so far)
