I am still not sure where to post this to question or discussion, I just want to talk with people, even if they don’t answer question directly you learn some new things. I post to discussion because I have feeling people will more interact than question.
Anyway lets back to topic. I am using UE strictly for realtime, I don’t see point of path trace when you have 3ds max blender and other tools that you are using for modeling to render in them, but ok maybe some really big scene to render. My main concern is real time, so my clients can walk through interior sometimes exterior. So where is the problem? Problem is mirror reflections. Now that I have really good hardware I can bake lightmaps really fast but when I see reflections I wanna cry, it will probably pass in game but not in archviz. Bake light give me best results, I can pack and use almost on any configuration (didn’t try on apple) but mirror reflection is pain, especially where mirror is rounded or shaped in bathroom etc. Is it possible to solve this? Also Bake light would save standalone VR instead using PCVR.
Lumen on other hand is great, when you apply anti aliasing TSR it gets really good, only problem is mirror reflection of reflections it has noise, but ok it can pass, problem there is everybody have to have good configuration. I was thinking about pixel streaming but I am noob in that field so I am not sure how that would go. Also I red lumen and ray trace that are on some beta stage or what with Nvidia, is it possible to try that?
What are your thoughts about this and what direction would you go in this situation archviz?
Sadly I do not have any awesome solutions for lumen reflections. I have been fighting with that for some time now.
But here are some things that have made it a bit better for me:
- Disabled everything that has to do with Screen Traces in the post process.
- Ray Lightning mode set to Hit Lightning for reflection (in post process and project)
- Enable Affect Ray Tracing Reflections in the light.
- “r.LumenScene.Radiosity.Temporal.MaxFramesAccumulated 12” (default is 4), this minimizes the movement of dots/shadows in the reflection.
These settings worsens the performance (gives me a drop from 50fps to 35fps in VR), but there might be other parts to optimize.
r.Lumen.HardwareRayTracing.HitLighting.Skylight 1 is a good deal when you got loads of open area with noise. the reflections may look a lil bland, but less noisy.
The only real problem with baked lighting and mirror reflections is that Lumen reflections are currently broken with it and will only sample the VLM, not surface lightmaps.
It’s annoying that the deprecated raytraced reflections were removed, and then Lumen’s lightmapped GI reflections were immediately broken the following version. 
then how to achieve good archviz mirror? use camera?? I watched some tutorial years ago on ue4 some guy use camera as a mirror, is that adequate solution?
doesn’t see big difference, as a matter of fact doesn’t see non, maybe it because my scene. I am using small scene to test everything at the moment.
Also I forgot to mention reflection on big portals aka glass? am I missing something here, I mean capture reflection is cool fake touch for reflection surfaces that are too far from point of view or they are some object that isn’t flat glass panel so you fake that reflection but on panel glass when I approach and see that spherical capture reflection my blood boils 
here is short test, don’t look at materials they are converted from Corona to Vray and exported via Datasmith 
What do you think it can go better. Note this is just test of Lumen.
p.s. where do you upload videos here?
No that’s completely insane and no one should be doing it.
If you’re in 5.5 you just have to wait for Epic to fix Lumen reflections with lightmapped GI.
Once it’s fixed, or if you are using an older version of Unreal where it still works (or deprecated reflections work), you should disable screen traces and use Lumen reflections with hit lighting.
Flat surfaces can use planar reflections, which is functionally similar to using a camera based mirror.
I would also avoid Nanite for archviz (or increase the fallback triangle percentage a bit)
why is camera insane, to me looks like good way around
what version is ok ?
I hold my interior scenes 3-5 million polygons, so Nanite is not big deal in interior, but large outside scenes with lot vegetation…
can you please elaborate this, you mean put behind every glass Planar Reflection? That look like tedious job but if it helps, maybe maybe maybe
Doesn’t make sense for glass, you need raytracing for that
5.3 and earlier, as I recall, they had deprecated raytraced reflections which worked with lightmaps. I can’t remember if Lumen reflections worked correctly with lightmaps in 5.4.
what if you are packing game for lets say gtx1080ti ? it doesnt support lumen? how then to achive reflections, mobile/tablet? This bothers me so much…
EDIT:
Just watched, RTX2000 series came in 2019 that is more than 5 years old (and they support lumen), I should not bother with gtx 1000 series hardware they are obsolete, so only for mobile/tablet/standaloneVR
you can use stationary lamps. only bake the gi not the lighting. and use megalights or, on mobile or low end, you would use the regular available shadow methods. or you would bake completely static lighting.
you have 3 choices (i posted in another thread)
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static lights bake lightmaps and lightmap volumes. no dynamic gi or dynamic shadows.
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stationary lights bake static gi and lightmap volumes. the lights can not be moved without invalidating the bake. but you get dynamic lighting and shadows (mega) and potentially lumen on top for dynamic (flashlight for example) gi.
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movable lights don’t bake anything. everything is rendered in realtime. all mega lumen.
this for example is using stationary lights aka baked gi as you can see from the black dot in the corner. and megalights doing the shadows. and raytraced for the directional lamp. the plant is a nanite asset, btw. works just fine.
a 100% stable image and stable mirror and glass reflections.
mirror is just material? is this approach good for pixel streaming (raytrace is slow for pixelstreaming)? Looks fine to me for PC version. What about packing for VR , there is only one option bake everything, and fake reflections?
yeh. in vr you can’t raytrace, right? too much of a performance drop?
- well… in this case you could go with distance field reflections. they are not as accurate, since it uses the global distance field by default, but… you can use a cvar to enable mesh distance fields for reflections for a lil bump in quality. (lemme check my lowend 5.4 project. been a while i opened that.)
looks like this with “r.Lumen.Reflections.TraceMeshSDFs 1” still noisy but does a decent mirror.
- or… you have to do the scene capture 2d trick for mirrors. this capture will render a full duplicate of the scene tho. this is considered expensive. and it’s basicly the same technique as planar reflections.
this is with baked gi. the lamps need a lil bit of indirect light boost to bake decent gi. the mirror is a planar reflections.
unfortunately none of this works in the vulkan android preview. i cannot confirm it is able todo that on a vr headset.
looks like a lot of testing need to be made