WebGL Shader Output Not Visible in Cesium (Gaussian Splat Viewer)

I’m having trouble with a Cesium splat viewer that we wrote in WebGL. It works stand-alone, but is not visible when we use it in Cesium. We use custom shaders based on GitHub - antimatter15/splat: WebGL 3D Gaussian Splat Viewer and have implemented usampler2D and vertexAttribIPointer in our own version of the Cesium library.

We’re not getting any errors from WebGL, but for some reason we’re not seeing anything drawn to the screen. I hid the globe to make it easier to see anything drawn anywhere, but I don’t see anything output on the screen.

We cannot run this is sandcastle because of the custom GL attributes we put into Cesium.

Any tips on debugging this?

Code available from my Git here:

Thank for for any help,
Brian