Comment by fuckcensorship | Hacker News Reader

Comment by fuckcensorship | Hacker News Reader

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> First off, there’s Lumen—a fully dynamic global illumination solution that enables you to create believable scenes where indirect lighting adapts on the fly to changes to direct lighting or geometry—for example, changing the sun’s angle with the time of day, turning on a flashlight, or opening an exterior door. With Lumen, you no longer have to author lightmap UVs, wait for lightmaps to bake, or place reflection captures; you can simply create and edit lights inside the Unreal Editor and see the same final lighting your players will see when the game or experience is run on the target platform.

Please correct me if I'm wrong, but isn't this basically a software-based implementation of NVIDIA's hardware-based RTX?

As mentioned by others, not really. Lumen can use either software or hardware raytracing as one of its components, but it uses them for different purposes. (One of the downsides of hardware raytracing is that you're limited to the very specific kinds of acceleration data structures that are supported by the GPU.)

This documentation page covers some of the differences between Lumen's software and hardware raytracing modes: https://docs.unrealengine.com/5.0/en-US/lumen-technical-deta...

And if you want a ridiculous amount of technical detail about how Lumen works, check out this talk: https://www.youtube.com/watch?v=QdV_e-U7_pQ

RTX is basically marketing term for Nvidia's hardware that can accelerate ray-tracing. Previously you had to interact with it through proprietary Nvidia APIs, but now there is DXR and Vulkan Ray-tracing, which allows to interact with other hardware or software implementations of these standards. AMD have hardware accelerated ray-tracing now(but it's quite slow tbh) and Intel just released their GPUs with hardware RT. Lumen is GI algorithm that builds on RT APIs. You can learn about it's inner workings here: https://www.youtube.com/watch?v=2GYXuM10riw

> Previously you had to interact with it through proprietary Nvidia APIs

That was never the case, OptiX was never intended for use in games. VK_NV_ray_tracing and DXR 1.0 were pretty much there since launch for the former and quite soon afterwards for the other.

I was talking about VK_NV_ray_tracing precisely, which is proprietary Vulkan extension. And I thought there was a similar situation with DXR(at first proprietary Nvidia extension and then common standard), but I was mistaken.

> I was talking about VK_NV_ray_tracing precisely, which is proprietary Vulkan extension

Khronos does not promote an extension to KHR until multiple vendors ship support for it.

VK_KHR_ray_tracing is a direct continuation of VK_NV_ray_tracing with very light code changes needed. (and nothing prevents a vendor from shipping support for the two)

RTX provides hardware primitives from which one could build portions of a global illumination solution. Lumen is such a full-featured, turn-key solution which I believe can run in "software" (as in not using dedicated ray tracing hardware functions) or can take advantage of hardware raytracing, including RTX, for some portion of its calculations.

Sounds like they have finally put in Global Illum - catching up to what CryEngine had years and years ago

Unreal is really starting to actually be the best of the best

Unreal was already the best engine purely on being easy to work with, support from third party programs and community, none of those things can be said about CryEngine.

From https://docs.unrealengine.com/5.0/en-US/unreal-engine-5-0-re...:

"Lumen implements efficient Software Ray Tracing, allowing for global illumination and reflections to run on a wide range of video cards, while supporting Hardware Ray Tracing for high-end visuals."

I would be surprised if it didn’t require an RTX to be useful.

Two things: while Nvidia's implementation of hardware ray-tracing is older and arguably superior to AMD's, they both have it.

And the Lumen / Unity demo was on a PS5, which is using (relatively low-end) AMD hardware.

So it isn't particularly logical to think you'd need Nvidia-specific ray-tracing for the feature.

Apologies, I meant hardware accelerated being required. The parent comment made it sound as if it were software rendering.

Lumen doesn't need any hardware implementation. It can use one if available, though.

apologies again, I forget how nit-picky this place is, what I MEAN is that it is only useful with hardware acceleration. I am sure a software render exists but I somehow doubt that it's ability to ray-trace in realtime works.

And to everyone else, yeah - it does run on next gen platforms no problem that also happen to have hardware accelerated ray tracing.

I'm telling you, I have a 1060 and it looks very very good. You can read on their documentation how they do it, but it basically doesn't need the RT accelerators, because they precompute the geometry, with SDFs or some other things I don't understand. The difference between RT hardware and just software is purely performance, but performance is good with just software.

It has a software implementation as well.

The PS5 demo looked useful.

PS5 demo did have hardware ray-tracing acceleration though.

that was my point too and I think all the comments beneath mine were willfully misinterpreting what I said.

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