DavidGraham
Veteran
I am assuming shadows for area lights are also ray traced hardware shadows?
Unreal Engine 5, [UE5 Developer Availability 2022-04-05]
- Thread starter mpg1
- Start date
I don't know of any categoric algorithmic errors (things are compared to the reference PT fairly frequently), but unfortunately there are still content details and approximations that can affect the output a lot. Specifically the quality of the BVH, but also sometimes managing the Lumen surface cache, particularly with complex meshes or lighting setups.
It's really great to be able to free artists in terms of light placement and such, and perhaps more importantly to just start to move towards the assumption that every light is shadowed! Conversely it was also a bit unfortunate to have to go back to a lot of chasing people about LODs, instance counts and the exact composition of how things are made in the scene. There's some wiggle room in that the RT scene does not need to be as high detail as the primary view, but when you use it more for direct lighting rather than just GI it starts to push the edges harder. And unfortunately there's really nothing we can do on the current generation to make things like BVH refits or TLAS builds any faster... the constraints on that side are effectively fixed until new hardware/APIs can help.
I presume there might be some talks at some point but seeing as it's all in the public source code/engine release, some high level points from my perspective **as of today** (this is all still very WIP, and will almost certainly change rapidly!):
1) Stochastic light sampling, but not ReSTIR
2) Handles local lights currently, all types (point, spot, rect, textured rect, etc)
3) Unrelated to the previous "raytraced shadows" path from UE4.
3) Raytraced shadows preferred (and used exclusively for the local lights in the demo), but can also be used for VSM SMRT projection, or a mix of both (selected per light, not a hybrid for a specific light). This is expected to be useful to folks who still need to use some VSM lights in cases where the RT geometry is not detailed enough. Ex. soft area lights use RT, sharp point/spot lights on detailed geometry possibly still using VSMs.
4) Per above, the path can still be useful even if no RT is being used at all, as it can accelerate and denoise VSM local lights pretty effectively. In scenes that are fairly well cached, this can be a performant option as SMRT projection performance could dominate in the past.
5) Directional lights not currently supported but no reason they couldn't be. Just less likely to be useful since they tend to affect every pixel anyways, tend to be sharper shadows, and suffer more from BVH quality/distance issues.
Correct. Per above the directional light is the only VSM in the demo, and it's only really visible as the soft moonlight and fog shafts.
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DavidGraham
Veteran
Awesome news! Previously Epic stated that they will streamline the shadow systems in the engine to just VSMs and RT, they said they will expand the use of ray traced shadows along side VSMs and mix and match between the two, I am so glad they kept true to their word and applied both techniques in a visually pleasing way.
For reflections there are currently 4 levels of doing them in UE5. You pick the one that suits your desired visual output/performance.
Software Lumen: basic RT with all the above errors.
Hardware Lumen: more accurate non screen space reflections (though aliased and poorly shaded with less detailed materials and shadows).
Hardware Lumen with Hit Lighting: more precise non aliased reflections and properly shaded, also use proper materials and shadows.
Path Tracing: reflections are pixel perfect.
megalights looks very cool.
UE 5.5 roadmap here. Haven't read through or watched the fest video yet.
@Dictator
That megalights demo is live on a ps5? Jesus.
UE 5.5 roadmap here. Haven't read through or watched the fest video yet.
@Dictator
That megalights demo is live on a ps5? Jesus.
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Yeah, that was the big reveal that had my jaw on the floor, I fully expected it to be running on a 4090, but on a PS5?
Well done, UE team.
I always forget some of this stuff is available a lot earlier in the experimental branches or something. Megalights looked pretty good a month ago. I'm sure people will find some compromises, but it's fast.
MegaLights | New Unreal Engine 5 Light Sampling Mode Comparison | UE5-Main
https://www.youtube.com/watch?v=TbZf6SANNbg [https://www.youtube.com/watch?v=TbZf6SANNbg] Taking a look at MegaLights today, MegaLights is a new experimental prototype light sampling rendering mode for Unreal Engine 5 currently available and being worked on in the bleeding edge UE5-Main branch...
cohost.org
cheapchips
Veteran
Since Megalights are 'experiemental' in 5.5, it begs the question of how quickly the feature makes it into productions? Is it a feature that can just be turned on mid or towards the end of development? Those dictate the timeline for shipping games using the feature?
Some features stay experimental longer than others. They really showcased it so maybe sooner than later. Maybe 5.6 or something?
Charlietus
Regular
A PS5 running megalights in that demo is the most technically incredible thing that we have seen from these consoles.
I don't think anyone thought that a PS5 could even run something similar to ReStir GI, not even in a demo.
Mind blowing job, @Andrew Lauritzen and team.
I don't think anyone thought that a PS5 could even run something similar to ReStir GI, not even in a demo.
Mind blowing job, @Andrew Lauritzen and team.
Thanks. That's great news and great work with MegaLight, the demo is really impressive (particularly when running on a PS5).
Please do not go back to software RT reflections (no character reflections pn mirrors and such reflective surfaces). That's a big regression for me (and plenty others I assume) and breaks whatever great the rest of the effects are doing for image fidelity. Like in Fortnite for instance everytime I don't see the reflections of my character.
Fantastic stuff. Hopefully this becomes the norm on the next generation of consoles. UE5 is killing it.
I hope they do deep dive videos on mega lights like they did for nanite and lumen. Wonder how many rays they’re casting per light per pixel and if there’s any sort of sample reuse involved.
No idea when UE6 will land but it will almost certainly be a refinement of these techniques and not a whole new rendering paradigm.
FWIW there's nothing special with megalights and geometry support - it's just whatever is in your RT scene (if using RT). WPO support in RT is just disabled by default since it is extremely expensive.
cheapchips
Veteran
30 second Megalights video from Epic in 4k
GhostofWar
Regular
I remember an nvidia video about rtxdi in their ue5 branch talking about how it enables lots of lights with less performance hit, is megalights pretty much the same thing? Ill go see if I can find the video in question and add a link if I can.
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