I believe I’m hitting Cesium issue #13041 with Gaussian splats from ion.
What I tested:
Multiple Gaussian splat PLY uploads through Cesium ion
Different assets and locations
Cesium ion preview
A local CesiumJS app using Cesium3DTileset.fromIonAssetId(…)
What happens:
The splats appear, but render incorrectly / smudged / broken
The issue appears both in ion preview and in the app
Environment:
CesiumJS 1.139.1
Windows
Vite + React app
Asset IDs: 4528138, 4528281
This seems consistent with:
opened 07:08PM - 20 Nov 25 UTC
type - bug
type - regression
category - gaussian splatting
### What happened?
Splats created from a PLY file via Cesium ion render differe… ntly in 1.134 compared to 1.345
**1.134**
<img width="480" height="384" alt="Image" src="https://github.com/user-attachments/assets/75def718-5080-438b-9b51-b3ae36283cef" />
**1.135**
<img width="446" height="415" alt="Image" src="https://github.com/user-attachments/assets/f43354d5-3865-4138-9ebe-dd8b10219267" />
### Reproduction steps
Run the code in Sandcastle using the 1.135 version of Cesium JS. Then compare the same code running in the 1.134 version of CesiumJS
### Sandcastle example
https://sandcastle.cesium.com/#c=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
### Environment
Browser: Windows
CesiumJS Version: 1.135 & 1.134
Operating System:Windows 11 Enterprise
(I moved this to the CesiumJS section).
There currently are a few open issues related to the splat rendering. The one that you mentioned, Regression in splats from PLY in 1.135 · Issue #13041 · CesiumGS/cesium · GitHub , usually has different visual effects than what can be seen in your screenshot. The screenshot looks more like the one from Jagged rendering for SPZ Gaussian Splats · Issue #12749 · CesiumGS/cesium · GitHub (and several forum threads). It may as well be that both issues are contributing here.
The good news is that there are several pull requests in the pipeline that address some of the Gaussian Splat rendering issues. Specifically, I think that Fix: Gaussian splat orientation and modelMatrix transform application by danielzhong · Pull Request #13245 · CesiumGS/cesium · GitHub will fix both the one from the PLY files as well as the “jagged” rendering.
You may want to try out the state from this PR locally, and see whether it resolves your issue as well (I think they will, but it’s always good to confirm this). I think the plan is to get this PR into the next release (but that’s not my call, eventually).
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