Raster Overlay Disappears When Using Overlay3 and Above

Cesium for Unreal
1

Cesium for Unreal Version: 2.14.1
Unreal Engine Version: 5.5 / 5.4
Platform: Windows

Description

When adding multiple Raster Overlays to a Cesium3DTileset, only Overlay0, Overlay1, and Overlay2 display correctly. Any overlay assigned to Overlay3 or higher disappears and does not render.

Steps to Reproduce

  1. Add a Cesium3DTileset to the level.

  2. Add several Raster Overlays.

  3. Assign them sequentially to Overlay0, Overlay1, Overlay2 (works fine).

  4. Assign any additional overlay to Overlay3 or higher → it disappears.

Observed Behavior

  • No errors in the output log.

  • Lower overlays remain visible.

  • Issue occurs regardless of layer source.

Initial Findings

  • Appears related to Cesium’s default material limit (MI_CesiumThreeOverlaysAndClipping), which supports 4 overlay texture slots.

  • Unreal Engine texture sampler limits may also be a factor.

Questions

  • Is this a hard overlay limit in Cesium for Unreal 2.14.1?

  • Can this limit be increased by modifying material/shader files?

  • Any recommended best practices for handling more than 4 overlays?

2

Hi @dua_saleem, welcome to the community!

Yes, as you’ve diagnosed, the default tileset material supports a maximum of three overlays.

If you need more, you’ll need to create a custom material, and you’re likely to run into Unreal’s sampler limits. Start by copying MI_CesiumThreeOverlaysAndClipping and in the new material instance add a fourth overlay material layer named Overlay3. If you run into the sampler limit, you can probably get around this by removing samples for features that you don’t need. For example, if you’re not using Cartographic Polygon clipping, you can remove the Clipping layer your custom material, which will save a sampler.

3

as of now, i am displaying world imagery as overlay0, country level as overlay1, high res img of AOI as overlay2, now i want to add wms and wmts layers but it doesnt show.

4

Hey @dua_saleem, did you follow the suggestions that Kevin posted above? If you did and you still can’t get things to work, please share screenshots of your material setup so we can understand what’s going on. Thanks!