Issues with ClippingPolygons (low performance, how to handle holes)

[mborjesson-bentley]

What happened?

Our users can upload their own feature-datasets (Shape, GeoJSON etc) to use as clipping polygons. We currently create our own pre-clipped 3D Tiles but we want to move the clipping into Cesium instead. To test this we set up a sandcastle-demo with a complicated GeoJSON with many points, but we noticed we get very low FPS.

We saw this related PR: #12650, will this improve the performance?

Also, is it possible to add polygons with holes in them for clipping? The GeoJSON used in the sandcastle below contains holes so some data should be visible, but from what I can see it's only possible to add outer rings, not inner rings.
Here's what the GeoJSON looks like:

Reproduction steps

1. Create one or more ClippingPolygons with many points, use for example this GeoJSON: https://ocpreleaseeudata001.blob.core.windows.net/support/sweden_4326.geojson
2. Add it to the default globe
3. Viewer becomes almost unusable, holes are not handled

Sandcastle example

https://dev-sandcastle.cesium.com/#c=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

Environment

Browser: Chrome 140.0.7339.207
CesiumJS Version: 1.133.0
Operating System: Fedora Linux 42

[javagl]

Regarding the performance: Here is that sandcastle on the CI build of the current main state, which already includes #12650:

https://ci-builds.cesium.com/cesium/main/Apps/Sandcastle2/#c=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

It's running at a stable 60FPS for me.

Regarding the holes:

It doesn't look like ClippingPolygon supports a PolygonHierarchy. (I don't know why, but technically, I think that it should be possible to do this). Details (reasons, workarounds) to be investigated.

[mborjesson-bentley]

That's great, thank you! Stable 60 FPS here as well :)