[SOLVED] Unreal Engine 5 - ray tracing integration with 'Lumen' and the future of NVIDIA's RTX

[alceryes]

I'm trying to find out more info regarding Unreal Engine 5's integration of many of the ray tracing functions with their new 'Lumen' function.

Will this supposedly bring AMD's ray tracing functionality to parity with NVIDIA's? Will older (but powerful enough) GPUs be able to enable Lumen and have ray tracing? Is this the end of NVIDIA's cards needing dedicated ray tracing hardware for games using Unreal Engine 5?
Concrete infoormation is difficult to come by. Please post any links with pertinent info. Also, this is just info gathering. Also, please save the red/green flame war for the schoolyard. This is just info gathering.

Some info I've found so far -

Unreal Engine 5 Migration Guide | Unreal Engine 5.0 Documentation

NVIDIA RTX, Unreal Engine 5 Define Future of Game Development and Content Creation | NVIDIA Technical Blog

Unreal Engine 5 (UE5) is available in Early Access, delivering the next-generation engine from Epic Games that will further propel the industry forward.

developer.nvidia.com

View: https://www.reddit.com/r/PS5/comments/gk72as/why_is_no_one_talking_about_lumen_a_potentially/


Edit: Another link.

 

[Bazzy 505]

your question is rather a broad topic to discuss here. Here's where your journey should start 😉

https://forums.unrealengine.com/c/development-discussion/unreal-engine-5-early-access/123

 

[alceryes]

Understandable.
I was hoping for some demo reviews with some of the latest cards but it's probably to early for that.

 

[hotaru.hino]

Will this supposedly bring AMD's ray tracing functionality to parity with NVIDIA's?

No. On top of NVIDIA being ahead of the game, NVIDIA also has a hardware accelerated BVH traversal. RDNA 2 does not have such, and does all the BVH traversing in compute shaders.

Will older (but powerful enough) GPUs be able to enable Lumen and have ray tracing?

In a manner of speaking, any GPU can run a ray tracing renderer. The problem is how fast it'll do it. NVIDIA shipped a ray tracing tech demo (Design Garage) you can run for the GeForce 400 series and with three 480s in SLI, it was interactive enough to play around with.

Also Lumen sounds like it's doing something called ray marching:

And if you want a demo of this using reflections: https://www.shadertoy.com/view/4dt3zn

The tl;dr is ray marching starts from the camera, but asks where is the closest point to the object from the camera. Then the ray travels a distance that lines up with that closest point. It keeps asking this question in the direction of the ray until some threshold is reached. This threshold is what defines how precise the result is, which limits how fine the details of the object can be before the ray marcher introduces artifacts.

This is an example of a ray marcher and what sort of "hits" it encountered at various thresholds (they call them distance field resolutions)

Ray tracing for the context of this question goes down to the triangle level, whereas ray marching typically does not. For global illumination, you don't really need precise, down to the triangle interactions because indirect lighting itself is imprecise.

Is this the end of NVIDIA's cards needing dedicated ray tracing hardware for games using Unreal Engine 5?

No. Hardware implementations will (usually) always be faster than software implementations. The only time we can start looking at getting rid of fixed function units is if the silicon space they take up for the feature they provide is no longer worthwhile if the general compute units can do it with reasonable performance. For example, we still have dedicated units for texture mapping, dedicated units for rasterizing, and at least on NVIDIA, a dedicated unit for vector processing. In a similar vein, if you want to do streaming and don't want to rely on the CPU to encode video, the usual recommendation that I'm seeing is it's NVIDIA only, because NVIDIA has a dedicated video encoder whereas AMD, while they have an encoding library, still does it purely through the compute units.

Granted the "software ray tracing" part of Lumen may get us a lot better global illumination and reflections than with last gen engines, but there may be artifacts that can only be solved by going down to the triangle level of intersection testing.

 

[alceryes]

Great info! Thanks @hotaru.hino!
I can't wait to see 'Valley of the Ancient' (or some other UE5 demo) running with the same UE5 settings, running lumens, on both the RTX 3080 and RX 6800 XT (with all other hardware specs the same).

Of course we'll need to wait till the full UE5 gets released for a true comparison.