Artifacts when rendering TopoJSON geometries on Cesium

Question

I am rendering a TopoJSON document, created via mapshaper.org from a shapefile, on Cesium. That works fine for all geometries except one. I have tried re-creating the TopoJSON document and re-editing arcs manually but I always end up with different geometry artifacts.

To me, it looks like some of the arcs have an incorrect coordinate in between, which leads to the self-intersections. But I am not able to debug the coordinate in question.

Also, when I remove arcs from the polygon manually, I end up with similar artifacts at different locations, which seem to be completly random.

Using "Check validity" in QGIS does not give me errors or self-intersections for the initial geometry, neither in the shapefile nor in the TopoJSON.

EDIT: I have displayed the outline of the polygon and it seems that the artifacts do not have an outline, which leeds me to the conclusion that this might be a Cesium rendering issue rather than an issue with the coordinates in the TopoJSON document.

Does anyone have an idea, how to debug or correct the polygon geometry?

Cesium rendered TopoJSON:

TopoJSON with some removed arcs:

TopoJSON with outline in black:

QGIS rendered TopoJSON:

Answer 1

Based on the assumption, that this is a Cesium rendering bug, I was going to check, which kind of geometries would be distorted.

It seemed, that the artifacts were appearing preferably along latitudinal boundaries in west-east direction.

I made a few tests:

A "simple" geometry along west-east looks good:

A geometry with a few more vertices already shows artifacts:

A geometry in north-south direction does not show artifacts:

A geometry in west-east direction also shows artifacts on the southern hemisphere:

Then I was going to split the geometry into multiple polygons to decrease the extent of a single geometry in west-east direction. After splitting it into sufficient small geometries, that seems to reduce the artifacts:

When removing the boundaries, it is visually not very obvious, that there are multiple geometries displayed.

This might not be an acceptable solution in some cases where a complete single-part geometry is neccessary but at least it enhances the rendering.

Answer 2

The problem was finally solved by setting the ArcType in Cesium:

entity.polygon.arcType = Cesium.ArcType.GEODESIC;