Artifacts in Polygon Fill (Holes) and Camera Zoom Issues with Custom Lambert Conformal Conic Projection in 2D Mode

What happened?

I am implementing a custom MapProjection (Lambert Conformal Conic) in Cesium. I am loading a GeoJSON datasource (countries) in SCENE2D with MapMode2D.ROTATE.

While the polygon borders (outlines) are projected and rendered correctly, the fills are rendering with significant artifacts (holes/gaps) or missing entirely. Additionally, the camera zoom behavior is erratic; I am unable to zoom in or out effectively.

Reproduction steps

Create a custom class implementing MapProjection using LCC math.

Initialize Viewer with sceneMode: SceneMode.SCENE2D and mapMode2D: MapMode2D.ROTATE.

Load a GeoJSON file containing country polygons.

Observe that borders align with the projection, but fills are broken.

Expected Behavior: The polygon fill should completely cover the area defined by the border, adapting to the curvature of the custom projection.

Actual Behavior: The fill appears fragmented with visible holes, suggesting a triangulation or granularity mismatch. The camera also locks up or fails to zoom.

Sandcastle example

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

Linked ticket :
https://github.com/CesiumGS/cesium/issues/3877
https://github.com/CesiumGS/cesium/issues/11096

Start with the linked Sandcastle example and the custom MapProjection implementation, reproducing the GeoJSON country polygons in SCENE2D with MapMode2D.ROTATE. Compare the behavior with issues #3877 and #11096; done means polygon fills cover their projected borders without holes and camera zoom works reliably.