I’ve made some tests with interiors and also witnessed the disco-like shadows. Is there a way to fix this, Lumen options, material settings? It looks like it’s mostly related to highly reflective surfaces. Looks like an underwater caustic effect applied to shadows.
Lumen is impressive and it capabilities look promising. While I’ve turned off Lumen and it features due to it’s heavy performance, I’ve seen what Lumen has the capability to achieve. So devs keep at it and keep up the good work. We’re all rooting Lumen’s success as this would lessen workflows and produce higher quality projects for us all.
I cannot get emissive materials to contribute to the GI. they just show up as a white whatever shape i put the material on with nothing beyond its shape when i view thru the visualizer for Lumen GI - I can see other lights contributing but no material - no color bleed or anything - watched several vids - all project settings are right - I’m in the Valley project - updated my drivers - rtx 2080 ???
Are there plans to implement a solution for mirror reflections?
I was hoping I could lean on planar reflections as a crutch, but I’ve been unable to get them to work with Lumen. Adding a planar reflection to the scene just tanks the performance and still only renders the lumen scene in reflections.
Also are there plans to improve the scalability options? Setting the quality slider for GI/reflections to 0.25 improved my frame time by 0.4ms, at the cost of an enormous drop in quality.
Ideally we’d be able to turn individual features off, at the lowest quality Lumen would essentially only provide skylight occlusion. Though I’m not sure how lumen works so I have no idea if that would actually result in a performance gain.
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Lumen does not like complex emissive material setups. I was working on this weird alien temple concept and here are the results I got. There is a very small amount of Exponential Height Fog enabled in this scene
Is the plan for RT shadows to support nanite assets for the final 5.0 release?
I mostly work on arch Viz, so Lumen is something that came from heaven for us, it is just great, our dream come true, Congrats to the team!.
But is not perfect yet for sure, most scenes that I prep in 3D Max or small scenes from Rhino works great.
But large models from REVIT seems to have this strange behavior, I have been trying to figure out, what’s the difference, maybe something related to Distance Fields but I am not sure, any of you have similar results?
Thanks.
As mentioned before, im general the system is amazing but reflections could improve, particularly for mirror like or highly reflective surfaces.
Also I’m seeing the Skylight reflected on translucent surfaces, such as glass, in interiors. Strangely if I enable cast ray tracing shadows on the Skylight this gets fixed but the light now casts noisy shadows everywhere. This happens even though ray traced shadows are disabled in the project settings. Never mind, I missed that the documentation says reflections on translucency is not yet supported.
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Even though this is basic idea, but I have to mention it…
Lumen: Cache and Pre-Cache.
Pre-Cache - pre-calculates the lighting in front of the player based on the movement trajectory (vector) and visibility.
Cache - stores the information about the ‘last’ lighting ‘condition’ in the level/area.
How it works: When a player (camera) moves towards some new area the engine pre-calculates the lighting in that area and stores that information in pre-cache. When the player (camera) enters the area, the engine doesn’t have to calculate the lighting from the start, but it uses pre-cache instead and continues calculating the lighting from there. After that, the engine stores the information about the lighting in a cache file from which it can recall it if the player decides to go back to the area. If the lighting ‘conditions’ changed since the last visit (e.g. doesn’t match the cache), the engine starts the pre-cache process again. Another option in that case would be to pre-cache (recalculate) the lighting only for changed light sources based on their radius of influence while loading the rest of lighting from the cache file.
Notice: I posted this as it’s own topic before I noticed this Lumen specific thread.
First off, just wanted to let the devs know that Lumen is a huge step forward and an amazing attempt to achieve the holy grail of realistic GI in realtime. So I’m coming from a place of praise and hope to better this already amazing system. With that said, let’s look the gift horse in the mouth and go over at the issues (at least the ones I’ve spotted and/or don’t know the work-arounds yet).
Virtual Shadow Maps (beta)
- Though these work excellently for point / spot / rec lights. When used with a directional light I’ve found that the resulting penumbras creep under and through surfaces like walls. So for example in my scene I’m wanting to emulate an overcast day outside, so the sun isn’t pin sharp but diffused. This results in the below effect.
Skylights
- It’s great to see these being calculated by Lumen, but at the moment the ‘Indirect Lighting Intensity’ slider seems to have no effect, so we’re stuck at a fixed contribution level for now. Would be great to see this slider having an effect. I’m using a dull overcast sky, so I could really do with pumping the bounced light in occluded areas without making the direct light outside blown out.
Volumetric Fog
This is the real sore spot for me particularly, but I can image as most people use vol fog to create some kind of ambience in their scenes, it’ll effect a lot of people.
- As far as I know there are no controls that relate to how Lumen interacts with your vol fog volume, it’s completely doing its own thing regardless of other sliders and switches you set elsewhere. And that ‘thing’ can get quite weird – see below. This is from just one directional light in the level; I’ve got bizarre streaks of light in the sky emerging from places where there’s no models or light sources. Also you can see the fog illuminance starts at about 2 meters above the ground for some reason.
- Each light you place in the level comes with a ‘Volumetric Scattering Intensity’ slider that used to allow you to control the contribution of that light to the fog volume. They still work for the direct light cast, but, even if you set that slider down to ‘0’ Lumen ignores it and continues to propagate the light in the fog. I think there are two features that would be great here, ideally both, but one or the other would work.
- A slider that defines Lumen’s global contribution to vol fog, whilst leaving light’s direct fog contribution intact.
- A ‘GI Volumetric Fog Scattering’ slider alongside the existing slider (which now becomes ‘Direct Volumetric Fog Scattering’). The reason for the separation would be to allow a directional light to illuminate fog outside directly, and to be able to control the illumination of fog in the bounced light.
- Emissives would also really benefit from the vol fog contribution slider / node in the material editor given that they have become more like regular lights via Lumen. In the shots below I’m using emissives to push light into a room, but when I turn on my vol fog the whole room become swamped in fog. So the ability to control that contribution would be much appreciated.
Emissives
- Also notice that emissives that update their material properties in realtime (colour or brightness for example) are often not reflected in Lumen’s GI. I’m presuming that’s because Lumen is doing it’s best to cache the output of lights.
Material Nodes
- expect this is coming further down the road, but the inclusion of material nodes that allow us to send different things to Lumen vs. the final raster would be excellent too. For example in my above scene I could hide the obvious emissive boards at the windows and still benefit from their output into the GI.
Well, that’s my 50 pence for now, really excited to see where the technology goes. Would like to hear if others have any feedback / solutions on my points or what to add more.
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So far things look great, though I don’t yet have a lot of time to really dive in.
What I’m mostly curious about at this time is whether it will eventually be possible to override the power of an emissive material. Right now it requires very high values to have bright lighting, which will overpower any texture applied to the material. An example would be a TV screen. At this point it looks really cool the way animated materials affect the lighting, but the material itself will just be glowing extremely brightly.
I’m developing a lighting sim in UE 4.26 and the most appalling thing I have found with this engine is it’s handling of light in the real world. Reflections don’t exist in dynamic lighting in 4.26 but in 5 they sorta, kinda, maybe work. By that I mean, it’s a hit or miss on material setup that will give any semblance of realistic light reflection, especially with sunlight and speculars.
I’m 65 years old, a master photographer, MS/Apple developer and have used Vue Infinite, Daz, Poser, iClone/CC and Blender for many years yet I keep scratching my head on how ambient lighting and reflections are handled in UE. I can understand the roots of this system being game based but Epic is constantly touting ‘real world’ lighting yet fails to deliver.
Don’t you guys have anybody at Epic that understands the importance of color temperature, specular reflections or ambient lighting as the baseline from which all other lighting must interact with?
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All of the volumetric items listed by Prizmizm are on my list as well. Fog volumetrics inside of buildings are a sore point with my development processes as inclusion/exclusion params are a PITA to setup in muliple locales.
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Those features would be awesome with lumen and fog. I’ve found that it behaves physically accurate how much light affects the fog. Managed to get this going: https://www.youtube.com/watch?v=4QQKe4JXqRQ
Not actually entirely sure whether this is a Lumen issue but there seems to be some problem with how exposure value is calculated for light from emissive surfaces.
Using Lumen and hardware support enabled, Burley subsurface scattering renders with artifacts (moving black dots) when used in large objects. This wasn’t the case in UE4.
Please add procedural mesh content support or make a document for writing a plugins for it.
Thank You 
When activating Nanite some Quixel assets get this weird effect like something is overlapping. Anyone knows why?
This is not a lumen problem, raytraced shadows are not yet correctly supported by Nanite. They trace against the proxy mesh which results in self-shadowing.
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Thank you.