From a technical standpoint, you are correct. The operation would be the same for tracing a ray, but as you’re penetrating through a surface as opposed to simply bouncing off of it, you’ll need to query values such as IOR or other media variables like subsurface color. Lumen supporting TwoSidedFoliage is probably an overlapping implementation with translucency, so I guess you’re right and a lumen refraction behavior would be absolutely possible. I just wouldn’t know what perf would look like, but I’d imagine recursive ray-tracing would probably be pretty expensive.
On the note of translucency, I would love for lumen to get caustics support. We know it can be done, NVRTX has done it, and courtesy of the surface cache, you can even accumulate the lighting on a surface and not pay a price when it’s not updating. Imagine light bouncing through stained-glass windows and lighting up a room.
Unfortunately, you cannot currently make lumen translucency solve anything other than perfectly-specular reflections. This is to remove the cost of a second denoising pass, and to my knowledge there is no CVar that can allow for rough translucent reflections. I am happy to be told I’m wrong though.
However, if you want rough lumen reflections for art purposes, you might want to play around with surface normal maps, or even disable HQ reflections and get the interpolated radiance cache reflections. They could do the job.
Indeed. I think the framework is there from other features but probably not a high priority as you said. Would be great to have though. The cost could get out of control if you had layers of translucencies, but it could fall back to screen space after the first object.
Plus we would probably need refraction to get caustics anyway.
Excellent work on the latest 5.1 release. I’ve spotted something that might be of note.
Right now it looks to me like skylights with Lumen are not affecting Volumetric Fog at all. This results in the volumetric fog being black, with no light received from the skylight. This was working fine in 5.0 and the 5.1 previews, so this is limited to the latest 5.1 full release afaik.
toggling r.Lumen.TranslucencyVolume.Enable to ‘0’ reverts vol fog illumination back to a non-GI mode (it is illuminated, but there are no shadowed areas anywhere, so fog in interiors is also illuminated as if it was outside). Which isn’t surprising as the command (when set to 0) prevents volumetric effects from receiving Lumen.
toggling back and forth between scalability modes (medium, high, epic, cinematic) produces erratic results - sometimes it stays black, sometimes it reverts to the non-GI mode explained above. At no point does it work as it used to.
Directional / Spot / Point light all still work as normal from what I saw. This bug (will refer to it as that for now) is limited to skylights - but maybe it’s a broader issue with indirect lighting in Lumen + Volumetrics.
Would be grateful if anyone could verify this is not just me or let me know if there’s some new Lumen setting / Post Process setting I’m missing.
I think you’re correct, and this is where lumen’s ‘1 bounce+fallback’ design paradigm seems to be very smart. Most of the valuable visual behavior is happening on the first bounce of the refraction/reflection/GI, but you still need something to stand in for the other bounces to account for energy loss. Using the translucency radiance probes for reflections after the first bounces makes a lot of sense, because that’s normally obscured enough that you wouldn’t even notice at first.
I think you’re right to a large extent on needing refraction for caustics. However, there could be a case where one could use a simplified transmission model to handle directional lighting, and receive simple colored shadows as opposed to full-on reflective or refractive caustics. This has the added benefit of being more coherent than arbitrary ray-tracing depending on the technique, but no doubt still a perf. hit.
I’ve been observing this behavior as well, both in myself and in other posts. Translucency skylight shadowing appears to be broken in the current version of 5.1, hoping a patch comes along soon.
Maybe someone will be useful. A three-layer wall helped me get rid of these glare / gaps in the sky. Sandwich. This is the cheapest way I’ve come find.
Initially I did one layer of walls 30 cm, but I was getting light leaks in concave/inner corners and where the cabinets are (the light was pouring over the wall where the cabinet leans) and light from the sky as in the post above.
Looking for a way to get rid of light leaks in the corners, I came up with a solution of double walls, 10 cm wall, 10 cm clearance and again a 10 cm wall (it’s all one mesh).
Now after looking for a solution to get rid of light leakage from the sky (as described in the post above) and came to the third wall 5 cm in the gap between the first two.
I don’t have RT X, only software tracing. what triple walls might affect in the future - I don’t know yet.
That’s a very clever strategy for reducing leaking, my one concern in a shipping environment might be memory costs- if the objects are instanced it wouldn’t be too bad, but it could potentially accumulate into a significant memory demand.
Hi,this is a 0 roughness metallic cube, seems like it only reflect lumen scene with low resolution materials and shadows , btw I cant use hardware raytracing , just wanna know if theres a way to fix this or get better results,thx
This is the expected result for software RT lumen. The “hit lighting” option offers better reflections over “surface cache” but beyond that you need hardware RT to get high quality mirror reflections.
Yes that is the same issue I mentioned earlier, seems to not have any fix for it unfortunately. Lumen high reflection quality seems not to be affected by roughness. But, you can reduce the intensity with reducing the metallic value. I thought it was only affecting translucency tho.
Rough metallic surfaces work fine. This isn’t the same issue. They are just hoping to get more accurate mirror quality reflections without hardware RT, which isn’t really possible.
I think I’m somewhat confused by what you’re saying @BananableOffense ? To my knowledge hit lighting was the highest quality lighting mode, and it required hardware RT. Correct me if I’m wrong, but hit lighting lets reflections evaluate direct lighting plus indirect lighting via the surface cache wherever reflection rays land, which gives full material and shading evaluation but only for direct light. Is there a higher quality lighting option I’m unaware of?
You’re correct - my response was poorly worded. If you’re already using Lumen Hardware RT with Hit Lighting, then its as good as its gonna get for now. Indirect lighting still looks pretty blobby and noisy in a scene with clean surfaces when viewed in mirror surfaces.
This is true, and I do find it somewhat frustrating. I read through the lumen 2022 presentation, and while I know they are doing filtering in order to make the surface cache not look distractingly bad, it’s still rather unacceptable from a reflections standpoint.
Of course, lumen working at all is a technological marvel, especially with the incredible performance demands of 60FPS games. Game art before real-time RT really couldn’t support smooth, non-leaky reflections like lumen can. For lower quality reflections though, I almost find it more helpful to think of lumen SF reflections as global parralax-correct cubemaps in terms of how you art around them.
The issue persists even if I deleted the post process volume… This is happening in all environments. The issue is gone only when I “disable multisample effect” in post processing in movie render queue, however, by doing so, I loose motion blur, depth of field, and other cinematic effects.
I’ll try with the normal map thank you!