i’m (re-)cloning right now, too. this will look good in my lil mirror room? without cheats. i’ll for sure not remove that from my lightlab. also… thx @Krzysztof.N
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I know the team is exceptionally busy, but just speaking as a member of the community, I’d be really interested to hear a retrospective on how lumen came to be as a system. While the end user only sees a quite remarkable piece of tech, I’d be genuinely curious to learn more about the development path, the experiments that didn’t pan out, the breakthroughs, etc.
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I didn’t and I don’t see it here in recent posts. Please link it.
It’s not really a retrospective, but it does describe first experiments and various failed ideas:
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Does this mean like proper refractions happening through multiple objects? Like stack of glasses for example? Or water in glass etc…
hmm. slw is working as intended on my end. even abused as a wall decoration. proper fog, coverage and reflection. not sure how you generated this screentrace there. i’m using planes btw, if that matters.
i personally disable screentraces. i don’t like the artifacts it generates in general (messed up outer edges on water planes) and especially when using multibounce reflection. i mean… this is the lab. i’d have to test the benefits in a gameplay and real performance bound scenario. i have it in the city park lite test level tho and it’s doing just fine.
(devnote: the details panel can be dragged all the way over the outliner. lost access to the upper tab windows. i had to reset the ui. and saved my default while at it.)
and a offtopic question: how long does ue5-main compile first time on the average user’s computer? it’s been simmering in vs22 for a couple hours now. laptop is not sweating, but it’s for sure taking it’s time on my low end cpu.
You’ve misunderstood the issue. Reflections of objects using SLW is broken. Meaning if you look at the water surface from a reflective material like a mirror or window, it will be mis-projected.
The cylinder is using SLW in my example, not the plane.
okay. that is “broken”. i mean… it’s an edge case where you abuse the shader for something it was not designed todo. water is usually flat. ez projection. it’s not a substitue shader todo glass.
either way. it’s just another artefact of screentracing. i don’t really need or use it for reflections. idc tbh. ¯_(ツ)_/¯
It would be broken even if you use it as intended. If you look at the reflection of a normal, flat plane of water within a reflective service the reflection would be projected onto the depth of the surface below, causing major parallax issues the deeper the water becomes.
If you don’t care, don’t distract or try to diminish the issue, because other people might.
yep. but… basicly it breaks cause the screenstrace is not great. offscreen is offscreen. that’s why i have those nodes in my game.
when vs is done simmering i’ll maybe try something. that’s gonna take a while, tho. gotta clean up this build. it’s bloated af. harddrive full. that’s a wtf.
i got enough mats to experiment.
tracing the water in the reflection is technically not hard. hit it, do a reflection bounce, passthru bounce and measure the distance to the underlying surface. you don’t have scene depth in the raytrace, which is present in the normal scene. then you evaluate the lower surface and fog blend and the reflection blend on top. shaders.
it’s a very niche case tho. who’s got a mirror by the pool or a deep fog puddle where you need to see the ground of it? you know?!?
That’s honestly a lot of what I was looking for, thank you! I was curious what the path was, as I noticed a lot of similarity between the ray-traced cards+DFAO solution that the original Samaritan demo used, and I was wondering if there was a more direct continuity from that to lumen, or a more meandering route. Thank you for sharing!
Hey guys,
Is it possible to get hard shadows and proper sunlight from a HDRI backdrop using Lumen?
Please see these two images. The first one is with lumen hardware raytracing, no sunlight or proper shadows from the sun of the HDRI, second one is pathtracer. Is there any way to achieve some kind of parity without using a directional light? (Which would of course make the pathtraced scene look incorrect, since it would have duplicated lighting from the sun)
Have you tried marking your window’s glasses as no Casting Shadows?
Yes. It does not make a difference unfortunately.
lumen is GI (and reflection) but not direct lighting. the sun shadow is a semi direct light cast. the pathtracer has this light information as it reverses all the way back to the sky and produces precise ray collision with the frame of the window to produce the sharp edge per pixel. lumen does not have that. it has a limited probevolume and surface hits and does not trace far enough to hit the sky sphere and grab the sun sample from the hdri texture. even if it would do that, the resolution of the surface cache texels will not produce a sharp shadow. it’s meant for GI. and has those limitations to get it to run in realtime. deal with it. put the sun in there. this is the way.
Thank you for the response, just wanted a confirmation that lumen does not support such feature.
Skylights even without lumen never supported it either.
My confusion come from the assumption that both the pathtracer and lumen uses some kind of raytracing, so it wasn’t clear for me why pathtracer is able to cast these shadows and lights, while the raytraced skylight or lumen can’t.
A reasonable misunderstanding. The difference between path tracing and raytracing is that pathtracing handles everything in a comprehensive way - direct light and shadow, reflection, refraction, transmission and bounced light are all determined by following the path of the light.
Raytracing generally refers to a suite of individual technologies that may do some of these things. For example, you can independently enable raytraced shadows, because shadow mapping is a separate tech from Lumen.
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path tracing and raytracing are technically similar. both shoot rays from the camera and at every hit point in the path. the hits are different tho. raytracing natively reflects into a singular direction. while path tracing shoots multiple rays from hit points. the thing they don’t have is… a clue of where the sun is at if it’s not a lamp. raytracing needs a sun lamp to evaluate the proper lighting at hit point. path tracing can shoot mulitple rays and eventually gather samples of it in the sky. importance sampling helps with that.