There’s a extremely niche issue with shadowing/MSAA under very specific circumstances in UE 5.5 that I’d like to share a guide for, if anyone else encounters this problem and would rather not spend hours on it. The error can manifest in various ways as terrain losing its light dependent on viewing angle to the light, distance to the camera, sky light and ambient light can seem to turn on and off randomly, or meshes can manifest as screen-space shadow ghost images.
It happens when using the following:
Forward Renderer, any MSAA. The error is not visible if not using MSAA.
Shadows enabled (r.ShadowQuality 1 or higher), MSAA (r.AntiAliasingMethod 3), and, (r.MSAAcount 2, 4, or 8).
Light is BAKED with a stationary directional light (and optionally a sky light).
The light has CSM shadows and distance field shadows.
A mesh, or multiple, has Distance Field Indirect Shadows and Affect Distance Field Lighting enabled. Distance Field Indirect Shadows seems to cause an issue here.
It can be tricky to find initially since accidentally enabling Distance Field Indirect Shadow on a mesh will cause problems for actors outside of it, not the mesh itself.
To fix the issue, look for any meshes with Distance Field Indirect Shadow in the MSAA project and uncheck it. CSM/DF shadows still work on movable meshes with Affect Distance Field Lighting checked. Bake lighting and ensure everything is ok.
For future searches:
The MSAA shadow error can appear as a dark ghost image of meshes, dark blobs on some meshes, directional light and skylight disappearing, a black line or rectangle covering the screen, missing lighting, dark ghost copies of meshes.
Hero post; thank you really helped me track down similar issue i was having. I wanted to tag on that I am experiencing an issue in 5.5.4 source build where forward shading and msaa with a spotlight configured with a very large attenuation seem to be causing shadow/lighting artifacts as well in the lighting pass. I’ve submitted a bug report with the following steps to reproduce
New project on unreal 5.5.4, this same setup wasn’t an issue in 5.4.2 that I was using before I upgraded
Turn on Forward shading and MSAA in project settings
Create any big floor/plane (static mesh or landscape, material doesnt matter)
Place a spotlight with about 16.0 EV (this doesnt have to be too precise) 25000 units above the floor
Set spotlight attenuation to 32000 so that the light reaches the floor
Zoom around in editor or in standalone game and you can see black line artifacts flicker in and out on the floor
Hi, did you ever find a fix for this? The same issue is plaguing me! It seems to affect every baked stationary point light and spotlight with MSAA and forward shading.
It is very simple to reproduce for me:
Create a new Blank project.
Enable Forward Shading and restart.
Create a spot or point light. (I created one with Location: -30.0, -170.0, 150.0; Rotation -156.3, -90.0, 163.2; Intensity 100.0 cd, all else default)
That’s it. I now get lots of weird horizontal black bars as I move the camera. It’s easier to see with the camera at a shallow angle for me, and when the camera is moving slowly.
