Does the current version of Cesium for Unreal support loading 3D tiles that utilize the 3DGaussianSplatting technology?

hzc123 · October 31, 2025, 2:49pm

janine · November 3, 2025, 8:24pm

Hi @hzc123,

We don’t officially support Gaussian Splats yet, but there is a draft PR open to add support here:

github.com/CesiumGS/cesium-unreal

Implement Gaussian Splats

main ← gaussian-splats

opened 08:00PM - 14 Oct 25 UTC

azrogers

+1837 -15

Closes #1670. This PR adds support for the `KHR_gaussian_splatting` extension in… Cesium for Unreal (and, by virtue of CesiumGS/cesium-native#1262, SPZ as well). It does this using the Niagara particle system to handle rendering the splats from a custom NiagaraDataInterface. A subsystem is used to collect the splats into the singleton Niagara system. This is very very experimental! Even when this gets merged I think we'll need to call it an experimental feature. But some things we should take care of *before* this makes it out of a draft PR: 1. Sometimes the assertion `ensure(GroupCount.X <= GRHIMaxDispatchThreadGroupsPerDimension.X);` fails in `RenderGraphUtils.h` as a result of Niagara trying to generate too many sort keys at once. This is maybe an inevitable result of trying to pack so many splats into a single Niagara system, but packing them all into a single system is necessary so they sort together (else we'd get some awful looking seams between adjacent systems). I've implemented a really dirty system to try to mitigate this (trying to avoid resetting the system more often than every five ticks), but a better solution is almost certainly needed. Ideally we can find a way to avoid this assertion that doesn't involve splitting the scene into multiple Niagara systems. 2. The Niagara system graph needs to be cleaned up. There's a lot of different code from a lot of different false-starts, rewrites, failed experiments, and other implementations I referenced (open-source implementations, license information for those implementations is included in the Niagara asset as a block comment). It would be good to streamline it into a finished implementation. Actually, it *might* be better just to do away with using the Niagara graph system entirely - just have the DataInterface provide a single function that takes in the index and matrices and returns all the splat information. That way we can have all of the compute shader code in the cpp file instead of putting it in a uasset that's opaque to git. 3. ~Some splat tilesets aren't positioned correctly. Particularly, the [Hines Rowing Center](https://sandcastle.cesium.com/?id=3d-tiles-gaussian-splatting) tileset from the Sandcastle hovers over the terrain. I had implemented a fix for this involving offsetting the position by the size of the bounding box, but I had to revert it because [*this* example tileset](https://sandcastle.cesium.com/?id=3d-tiles-gaussian-splatting-comparison) from the other Sandcastle example is in the right position already, and would be offset into the wrong position. I'm not clear on what I'm missing here that has one working and one broken.~ ✅ The Hines Rowing Center tileset is just based on the ellipsoid instead of CWT. 4. Can the visual quality be improved? To me the sample datasets look blurry compared to the Sandcastle examples, but other splats loaded in other Gaussian Splatting projects in Unreal *also* look blurry. I don't know if we're just all doing it wrong or if this is a consequence of something Unreal is doing or what. It's also possible I'm just psyching myself out and it looks fine. 5. Can the performance be improved? The shaders are very unoptimized. It's likely we could improve on some of them. 6. ~I haven't yet tested it in a packaged build. It's likely the way I'm loading the Niagara system in the subsystem could break with a packaged build.~ ✅ Should be fixed in [1476ee2](https://github.com/CesiumGS/cesium-unreal/pull/1748/commits/1476ee25873f2daf0e641673c1118253c697983a). 7. The singleton actor holding the singleton Niagara system needs to be hidden in the editor. This shouldn't be difficult, I've just been skipping it for now because it's useful to be able to interact with the temp actor in the editor for debugging. 8. [This issue.](https://github.com/CesiumGS/cesium-unreal/pull/1748#issuecomment-3406687254) 9. ~[Compute shader issue on Mac laptop.](https://github.com/CesiumGS/cesium-unreal/pull/1748#issuecomment-3407599571)~ ✅ Fixed in [0695d2b](https://github.com/CesiumGS/cesium-unreal/pull/1748/commits/0695d2b44b577511a50d05a4e039e485b06298d2). 10. [Floating point precision issues.](https://github.com/CesiumGS/cesium-unreal/pull/1748#issuecomment-3407749676) 11. ~[Sideways tileset issue (possibly gltfUpAxis?)](https://github.com/CesiumGS/cesium-unreal/pull/1748#issuecomment-3444589923)~ ✅ Incorrect `gltfUpAxis` value that was being ignored by CesiumJS.

It’s still a work-in-progress, but feel free to try it out and let us know how it goes!

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Does the current version of Cesium for Unreal support loading 3D tiles that utilize the 3DGaussianSplatting technology?

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