Hi Kevin and thanks for a quick reply!
So I have created new project based on your CesiumForUnrealSamples project, moved the Georeference Origin at the same location my project is located at (somewhere in middle of Oslo, Norway).
I have then changed from the Cesium World Map/Terrain to the Google Photorealistic 3D Tiles.
Next I cut out a small piece of the Google Photorealistic 3D Tiles using the CesiumCartographicPolygon and added a simple ground plane for better visibility of the issue.
Next I added in some large boxes representing my buildings.
The last thing I have done and when I see the issues appear is when I turn on Lumen, this is not enabled in your default project settings.
And again here you can see the difference with and without Cesium visible.
Without Cesium:
With Cesium:
Here are my scene components:
And here is my project render settings:
This is a fairly normal Unreal 5 lighting setup with no special settings enabled. In my own project I am using the Ultra Dynamic Sky plugin for lighting but as you can see in this example I am using your CesiumSunSky Actor.
It seems like the issue goes away as soon as I disable “Use Hardware Ray Tracing when available” in the projects settings under render settings:
A bit unfortunate that we cant use the higher quality raytracing for lumen.
The pop up of cesium/google geo inside the CesiumCartographicPolygon unfortunately still happens here but is very based on camera angle and distance:
Again thanks for the quick investigation into these issues, best regards Magnus!