4.13 Lighting underside of meshes incorrect

Hi All,

Since updating to the initial 4.13 preview we had some improvements in our dynamic lighting for our project, however since then with the following updates (the latest 2) all downward facing meshes have changed their lighting as if they’re not 2 sided even though both the materials and meshes themselves are set as such. I have toggled the two sided settings on/off and changed materials but it hasn’t changed the outcome. I’ve shown the example for one project below however it has happened across all 3 projects I currently have in 4.13 with the same files in 4.12 not having the lighting issue.

The images show the difference with (original being the earlier iteration of 4.13) you can see they have an odd shading of a yellowy colour, you can see in the roof space that the upwards faces remain the same in both instances which look normal.

Because I have no idea what cause this Im not really sure what further useful information I can provide, please let me know if you need further detail, thanks!

HI Kyle,

I’ll need more information to proceed on this one. There isn’t a whole lot to go off of without a lot of guess-work on my part.

When I set up a scene with some Editor Planes with a two-sided full-white material and then only use a movable skylight and movable lights for the default level I don’t see any kind of change that would reflect what you’re describing.

It’d be nice to know the following in order to proceed:

  • Can you reproduce the issue in a blank project or a newly created level in your project?
  • Can you post a screen shot of your modified Directional/Spot/Point light and skylight settings?
  • Can you post a screenshot of your basis material setup and modified settings for the material.
  • If you have a sample project where this can be replicated that would be helpful if you don’t know the exact repro steps, but if you have the detailed repro steps that is helpful as well.

Thank you!

Tim

Hi Tim, thanks for taking the time to have a look!
I have attached all the screens you requested, or at least I think I have.

In a new level the mesh look even worse as it doesn’t have the additional lighting attached as ‘New Level’, this is with a variety of materials the underside always black, when lit with a point light it still shows as a black colour.

I’m not sure entirely what you mean by ‘replicate’ short of making a new project and dropping the meshes in so that’s what I’ve done ;D The meshes work fine, however if I import the ceiling meshes that worked before into any of my existing 4.13 projects I get the same black result?

Thanks again Tim, Goodluck!

Using your lighting settings and my test map with the default level and some editor planes doesn’t seem to reproduce anything that you’ve shown in your original post. Looking at your image with your last comment things look as I would expect at far distances and bleed from dynamic shadowing. Since you’re using DF’s accounting for the DF resolution of the mesh is important as well, and understanding that they don’t work well for very large meshes, if this is one single mesh, that is.

When I asked you to try and recreate in a blank project, it wasn’t to remake the project, but to try and reproduce the issue you are trying to confirm, but with basic assets or things that can easily rule out content creation issues and to show that there is an engine bug here. Remaking the whole project/level would really be ideal. :wink:

Mostly what I see here isn’t an engine bug, at least that I can reproduce from your OP. At this point, I think if you have a test project that can reproduce this it would be most helpful using the basic assets in the Engine Content folder or simple shape meshes from the modes panel.

Also, I did notice some confusing setups with your Directional light that likely need some clarification, though.

  • You have the option for Dynamic Indirect Lighting enabled. Are you using Light Propagation Volumes (LPV) by enabling this in the consolevariables.ini? If not, this setting doesn’t do anything.
  • Far Shadows - You have a value of 5000 set, but this will not be used since the Dynamic Shadow Distance is further than this value.
  • Distance Fields Shadow Distance: The value for your DF Shadow Distance is lower than your Dynamic Shadow Distance for Cascaded Shadow Maps, The Cascaded shadow maps should be lowered here and use the DF shadows for the farther distance. It’s cheaper to use DF Shadows at the distance than CSMs.

Hi Tim,

Thanks, as I said it was working properly before the latest patched so Im a little confused, Ill try rebuilding the mesh in ArchiCAD>Blender and hopefully I get some luck.
Thanks for explaining the lighting settings too, my actual job in in architecture so Im trying to piece together UE4 from no prior game dev experience hence why my lighting set up makes no sense :stuck_out_tongue: The results are incredible though, game changer for my clients! Ill let you know how I get on with rebuilding the mesh when I get a chance, thanks! Kyle

Lighting is one of those things where there are a lot of options and different types. It definitely takes time and practice to get it, and even then you are still continually learning new things all the time. :slight_smile:

Since you’re doing ArchVis here is a post I had made a while back with some helpful resources that may help in your endeavors.

Thanks Tim, I’ll have another look at these, the biggest challenge we have found from an ArchViz perspective is that we need external and internal lighting to look good within one project - however most tutorials focus on either external or internal lighting separately. With our workflow as well, large meshes are unfortunately a necessary evil to keep our production time feasible, this also means that UV lightmapping and baked lights are out of the question for now :frowning: which is scary because ideally we’d like to get our projects into VR but with our dynamic lighting we’re only getting 50FPS in places runing a GTX 1080 (admittedly on epic settings and 1920 x 1080 res) so I definitely have many many more lighting related settings to learn to improve on this! Ta, Kyle

Dynamic lighting can be tricky to get looking correct in some things since there is no dynamic GI atm.

For internal and external lighting I think using some post process volumes to help shift the tones and get things in a more desired look can help here to soften or lighten some areas and bring the contrast to where it looks good. Right now, lightmass just cannot be beat for this and the quality that can be achieved, but it does take time, preparation, and needs to be part of the focus from the get-go. If you’re intention is to not use any static lighting at all, I would recommend going into the Project Settings > Rendering > Lighting and disabling “Allow Static Lighting”. This can save you a little bit of overhead for it.

I’ve not done a lot of dynamically lit scenes in VR for comparison, but perhaps some of the settings in our VR Best Practices page can help if you’ve not seen it. Specifically Instanced Stereo, I would think, should help in some cases with performance.

In 4.13 (if you intend to move the project there) also has Shadow Map Caching, which helps with any dynamic point/spot lights that are not moving. This will capture the shadow for the dynamic light and until reuse it until the light moves or the mesh moves. This definitely helps keep these light types more affordable, so that may also help in this situation (notes on it are in the 4.13 release notes).