I’m tinkering with night scenes using Cesium for Unreal (UE 5.2.3 and latest Cesium plugin). I’m was struggling with why my clouds were still bright at night then noticed a weird shadow mesh on the OSM buildings.
It appears that the sun is shining through the tiles.
Normally this would be “fixed” by switching on two sided material but this isn’t a thing (that I know of) for the cesium terrain tiles.
Is there a proper fix for this? I suppose I can fake it a bit by just making a huge sphere just slightly smaller than the smallest terrain.
I turned off updating in editor and the shadow grid goes away. This and the shape (as the shadows appear to be the tile skirts) are what lead me to believe that the sun is leaking through the terrain tiles. Also the underside of my jets there are all lit up as well as clouds when I had them on.
EDIT: Just adding a note that the Giant Sphere idea didn’t work. I ended up putting a large squashed cube just under the surface of the tiles to block out sun leakage. Without a world anchor so it will “follow” me around to different places. Feels like a kludge. Probably because it is.
Hi @BDelacroix,
I’m far from an expert in Unreal lighting, so I’m struggling to understand what we might do to improve the situation here. We could add an option to force tiles to use double-sided rendering maybe? Come to think of it, I wonder if that can be achieved by end-users by creating a custom material? Double-sided rendering comes with a cost, though, so is that really the only way this problem is usually solved in UE? It seems slightly strange to me (in my admittedly naive view) that Unreal’s shadow rendering would not allow geometry to cast a shadow when the light shines through the back side of it.
I can’t call myself an expert either. I’ve been on a UE crash course since last September.
My guess is the world object is so big that part of it is culled out therefore the sunsky sun has no object to occlude it mathematically when the sun is down (IE: on the other side of the world.) I’d say it is odd the tile skirts seem to cast shadow, but then those would be doubled with adjacent tiles so that at least is explainable.
I don’t have a clear answer for you, but I do think it’s worth disabling Lumen and/or “Use Hardware Ray Tracing When Available”, as mentioned in the thread I linked previously, just to see if that helps at all.
