Question DF: Fortnite's Unreal Engine 5 Upgrade Reviewed - ( UE 5 reduce the need for HW RT?)

Heartbreaker

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I just watched Digital Foundry analysis of the Unreal Engine 5 upgrade to Fortnite.

It's Lumen Global Illumination Software mode looks as good as HW version most of the time - Very impressive.

If more games use UE5 then I think most people don't really need to be that concerned about HW RT, while still getting excellent Global Illumination:

 

Carfax83

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I don't have time to watch the entire video, but does it say how much of an acceleration factor hardware provides over software?

And yes I agree that Lumen is definitely very impressive for a software solution.
 

DAPUNISHER

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I don't have time to watch the entire video, but does it say how much of an acceleration factor hardware provides over software?

And yes I agree that Lumen is definitely very impressive for a software solution.
according to this Hardware Times article from last April, it is more aptly dubbed hardware deceleration.

Lumen also comes with hardware ray-tracing, but most developers will be sticking to the former, as it’s 50% slower than the SW implementation even with dedicated hardware such as RT cores. Furthermore, you can’t have overlapping meshes with hardware ray-tracing or masked meshes either, as they greatly slow down the ray traversal process. Software Ray tracing basically merges all the interlapping meshes into a single distance field as explained above.

https://www.hardwaretimes.com/unreal-engine-5-lumen-vs-ray-tracing-which-one-is-better/
 

eek2121

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I just watched Digital Foundry analysis of the Unreal Engine 5 upgrade to Fortnite.

It's Lumen Global Illumination Software mode looks as good as HW version most of the time - Very impressive.

If more games use UE5 then I think most people don't really need to be that concerned about HW RT, while still getting excellent Global Illumination:


I don’t think anyone is saying you can’t do quality lighting with shaders. The thing is, if you have a proper hardware RT implementation, that frees up computational power for things that aren’t lighting.

The issue is that hardware accelerated RT is still very much in the early stages. Eventually, GPU vendors will get to a point where using RT is faster, because of what I mentioned above. We are still quite a ways away, however.
 

GodisanAtheist

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Given the popularity of the UE engine, Lumen kinda kicks a lot of the hardware Ray tracing debate in the balls.

Raster lighting was obviously not accurate, but looked great. Now lumen comes along and gets us from 90% of the way to 98% of the way to proper RT again without dedicated hardware and decent performance... I'm left scratching my head on the value proposition of HW based RT right now.

Wonder if other engine devs have similar systems on the horizon...
 

Insert_Nickname

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Given the popularity of the UE engine, Lumen kinda kicks a lot of the hardware Ray tracing debate in the balls.

Raster lighting was obviously not accurate, but looked great. Now lumen comes along and gets us from 90% of the way to 98% of the way to proper RT again without dedicated hardware and decent performance... I'm left scratching my head on the value proposition of HW based RT right now.

Wonder if other engine devs have similar systems on the horizon...

I wonder if you could use hardware for those last 2-10%? Where it'd really matter. It would also cut the processing requirements, so low-end APUs/cards could make use of dedicated hardware.

Something like the 6500XT might have dedicated ray tracing hardware, but that hardware is too weak that you can actually make use of it as is.
 

gorobei

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Given the popularity of the UE engine, Lumen kinda kicks a lot of the hardware Ray tracing debate in the balls.

Raster lighting was obviously not accurate, but looked great. Now lumen comes along and gets us from 90% of the way to 98% of the way to proper RT again without dedicated hardware and decent performance... I'm left scratching my head on the value proposition of HW based RT right now.

Wonder if other engine devs have similar systems on the horizon...
i posted this last year. they cover unrealengine5 and frostbite. the frostbite surfel system seems more adaptable and less reliant on hw rt.


as far as performance being better on software:
at 32:03 in the nanite video he goes over the software raster being 3x faster than hardware. with mesh shaders prioritizing small triangles, the small fiddly bits just saturate even simple dedicated hw resources.

at 46:55 he goes into shadows needing to be fine detailed for self-shadowing. because their mesh/lod system is complicated and the rt api isnt flexible enough there is no way to hardware ray trace it.

it feels like they are getting into territory where some of the solutions they have for getting more fine detail is complicated enough that simple calls on rt functions arent going to be able handle all the other stuff going on elsewhere in the pipeline. until a game/render engine is intended to only be rt from the start, there isnt going to be enough resources to do something really impressive with rt effect(at least not on monolithic dies). this may change when you have a chiplet gpu with a main block chiplet and multiple separate accelerator/cache chiplets. but that feels like it is a decade away as far as enough gamedev studios converting over to that 100% rt engine paradigm.
 
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Carfax83

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according to this Hardware Times article from last April, it is more aptly dubbed hardware deceleration.



https://www.hardwaretimes.com/unreal-engine-5-lumen-vs-ray-tracing-which-one-is-better/

If that is the case, I have no doubts that it will be temporary. One thing I have learned over the years is never underestimate Nvidia's ability to optimize a process, whether through hardware and or software. Apparently, the shader execution reordering in Lovelace can increase performance in these workloads substantially. It's just a matter of time before they get around to properly optimizing it for their hardware.

Also, another reason why the hardware acceleration may be slower (especially on the consoles) is because the CPU becomes burdened with BVH building.
 

Carfax83

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Given the popularity of the UE engine, Lumen kinda kicks a lot of the hardware Ray tracing debate in the balls.

Raster lighting was obviously not accurate, but looked great. Now lumen comes along and gets us from 90% of the way to 98% of the way to proper RT again without dedicated hardware and decent performance... I'm left scratching my head on the value proposition of HW based RT right now.

Wonder if other engine devs have similar systems on the horizon...

No way Lumen is that close to real ray tracing. First off, full ray tracing is extremely rare and the vast majority of ray tracing implementations are hybridized. Portal RTX just released and that game uses full ray tracing without hybridization and by all accounts, it's extremely heavy. As powerful as Lovelace is, it would be brought to its knees if it had to run an advanced 3D game like the Witcher 3 with full ray tracing. It would be single digit frames, and the RTX 4090 would run out of VRAM.

Lumen looks great don't get me wrong, but I think equating it to actual ray tracing is a mistake.
 
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Leeea

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Lumen looks great don't get me wrong, but I think equating it to actual ray tracing is a mistake.
If you define ray tracing as rays being cast and reflected, Lumen is real ray tracing.

The trick they are doing is to not cast the entirety of every ray and all its bounces every frame. By selecting which rays to cast, spreading the casting of the rays over multiple frames, and using an algorithm optimized for CPUs they are getting away with just console level hardware.

It is very impressive.
 

Mopetar

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I don’t think anyone is saying you can’t do quality lighting with shaders. The thing is, if you have a proper hardware RT implementation, that frees up computational power for things that aren’t lighting.

The issue is that hardware accelerated RT is still very much in the early stages. Eventually, GPU vendors will get to a point where using RT is faster, because of what I mentioned above. We are still quite a ways away, however.

Getting enough RT hardware to do a reasonable job is still generations away to do full hardware ray traced lighting on anything current generation. Just look at how much Portal cripples current generation Lovelace cards. Outside of a 4090 it's not even playable even with DLSS turned on.

Fake lighting will almost always be preferable because you can make it do whatever you want. If you're using ray tracing, you have to design levels or the game world with the realistic lighting model in mind. Then you have to fake it anyway because the low end cards won't have enough to RT power to run the game if it's pure RT.
 
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Carfax83

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If you define ray tracing as rays being cast and reflected, Lumen is real ray tracing.

The trick they are doing is to not cast the entirety of every ray and all its bounces every frame. By selecting which rays to cast, spreading the casting of the rays over multiple frames, and using an algorithm optimized for CPUs they are getting away with just console level hardware.

It is very impressive.

The reason why I said software Lumen isn't ray tracing is because it can't do off screen reflections.
 
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fleshconsumed

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Very impressive. And even if it's not fully equivalent to HW RT, so long as it looks good enough, 90% just as good is perfectly fine to me. Considering that it's a lot more economical to get 16 core CPU that will be capable of pulling SW RT rather than 4080/4090 level card that is practically necessary for HW RT, I'm all for developers going software route.
 

maddie

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No way Lumen is that close to real ray tracing. First off, full ray tracing is extremely rare and the vast majority of ray tracing implementations are hybridized. Portal RTX just released and that game uses full ray tracing without hybridization and by all accounts, it's extremely heavy. As powerful as Lovelace is, it would be brought to its knees if it had to run an advanced 3D game like the Witcher 3 with full ray tracing. It would be single digit frames, and the RTX 4090 would run out of VRAM.

Lumen looks great don't get me wrong, but I think equating it to actual ray tracing is a mistake.
Someone thinking that gaming and the visual effects used are real. Meta, you still have a future after all.
 
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Carfax83

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Someone thinking that gaming and the visual effects used are real. Meta, you still have a future after all.

Is English your first language? I have no idea how you were able to construe from my quoted paragraph that I must somehow think ray tracing is "real."

Ray tracing is just a simulation of the behavior of light, and some simulations are more realistic than others. Realistic simulations tend to require a lot of computing power. Ray tracing is probably the most realistic depiction of light's behavior we have at the moment and consequently, it's extremely compute intensive.

Lumen is nowhere near on the same level as ray tracing in terms of simulation, and is more restricted. The fact that it can't do off screen reflections is very indicative of that.
 

maddie

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Is English your first language? I have no idea how you were able to construe from my quoted paragraph that I must somehow think ray tracing is "real."

Ray tracing is just a simulation of the behavior of light, and some simulations are more realistic than others. Realistic simulations tend to require a lot of computing power. Ray tracing is probably the most realistic depiction of light's behavior we have at the moment and consequently, it's extremely compute intensive.

Lumen is nowhere near on the same level as ray tracing in terms of simulation, and is more restricted. The fact that it can't do off screen reflections is very indicative of that.
Imagination deficit?

Once it can fool the brain, it's good enough.

So you look off screen?

:eek:
 
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Carfax83

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So you look off screen?

:eek:

When you're playing a game and your character looks at a reflective surface like a mirror and you see nothing, or a smear or glob instead of the actual character, that's because the image is off screen and not ray traced.

That's obviously not realistic. Ray tracing supports off screen reflections because it emulates the proper behavior of light. Lumen does not support off screen reflections because it's a much lower level of simulation.
 

Spjut

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Yeah, I consider Lumen "close enough", and with it not requiring a DXR capable GPU, I wouldn't be surprised if DXR support slowly disappears from the list. It's not the first time a shiny new hardware feature was added but never really took off because the studios found them too limited in practice compared to software solutions.

But actually a seriously intended question, can anyone explain why seeing your character in a mirror suddenly has become a difference between having raytracing activated or not in games 2022?
Plenty PS2 era games had them. Even Mario 64 had it. On PC, of course Doom 3 had it. Whatever workarounds they were, they were running on 20+ year old hardware.
 

maddie

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Yeah, I consider Lumen "close enough", and with it not requiring a DXR capable GPU, I wouldn't be surprised if DXR support slowly disappears from the list. It's not the first time a shiny new hardware feature was added but never really took off because the studios found them too limited in practice compared to software solutions.

But actually a seriously intended question, can anyone explain why seeing your character in a mirror suddenly has become a difference between having raytracing activated or not in games 2022?
Plenty PS2 era games had them. Even Mario 64 had it. On PC, of course Doom 3 had it. Whatever workarounds they were, they were running on 20+ year old hardware.
Whatever it takes.
 

GodisanAtheist

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Yeah, I consider Lumen "close enough", and with it not requiring a DXR capable GPU, I wouldn't be surprised if DXR support slowly disappears from the list. It's not the first time a shiny new hardware feature was added but never really took off because the studios found them too limited in practice compared to software solutions.

But actually a seriously intended question, can anyone explain why seeing your character in a mirror suddenly has become a difference between having raytracing activated or not in games 2022?
Plenty PS2 era games had them. Even Mario 64 had it. On PC, of course Doom 3 had it. Whatever workarounds they were, they were running on 20+ year old hardware.

-I too think the reflection argument is grasping at straws.

I think UE5 with all the bells and whistles will have to prove itself one a proper next gen game that looks more like their tech demo.

They have included HW accelerated RT in the engine, but maybe in a game like fortnight the limited RT cores in modern hardware are more of a bottleneck given the game's basic graphics.
 
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Aapje

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But actually a seriously intended question, can anyone explain why seeing your character in a mirror suddenly has become a difference between having raytracing activated or not in games 2022?
Plenty PS2 era games had them. Even Mario 64 had it. On PC, of course Doom 3 had it. Whatever workarounds they were, they were running on 20+ year old hardware.

That's actually pretty easy, because you only see your reflection if you are straight on. So they could just show a frontal shot of the player. If the environment is non-destructive and such, the background is fixed too.

So it's easy to fake without RT.
 

Mopetar

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Most games aren't going to look as good as the tech demo because they need to run on consoles and that always limits them. Maybe once the next generation of consoles come out and someone makes a title that isn't getting released on the previous generation, but those are rare.
 

Carfax83

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Yeah, I consider Lumen "close enough", and with it not requiring a DXR capable GPU, I wouldn't be surprised if DXR support slowly disappears from the list. It's not the first time a shiny new hardware feature was added but never really took off because the studios found them too limited in practice compared to software solutions.

Unlikely. Lumen supports hardware accelerated ray tracing as well which has higher quality and ray traced reflections. Ray tracing won't be going anywhere, because it's the future. Lumen is just another step on the path to full ray traced games.

But actually a seriously intended question, can anyone explain why seeing your character in a mirror suddenly has become a difference between having raytracing activated or not in games 2022?
Plenty PS2 era games had them. Even Mario 64 had it. On PC, of course Doom 3 had it. Whatever workarounds they were, they were running on 20+ year old hardware.

Because of the high rendering costs. Those games you cited used tricks and workarounds which can only be used sparingly. I remember Batman Arkham Asylum had a mirror in one of the rooms that showed Batman in its reflection. Apparently it was done using "a second viewport that was projected onto geometry as a texture."

Functional Mirrors (Concept) - Giant Bomb

Stuff like that obviously can't be used for an entire game, which is why they were so rare. Ray tracing is the only real global solution.