check for adjacent duplicate positions in GroundPolylineGeometry

[likangning93]

@OmarShehata noticed that adjacent duplicates were crashing polylines on terrain.

[cesium-concierge]

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[likangning93]

Just realized this also isn't really sufficient, same lat/long but with different heights will still cause problems.
I'll fix this soon.

[hpinkos]

@likangning93 yeah, I would just set height = 0 for each position, then remove duplicates. We do that for other geometry types like the corridor

[likangning93]

Up-to-date and passing

[OmarShehata]

Just tested it out in my sandcastle example (#6692) and it seems to resolve the issue!

[OmarShehata]

Actually, I just encountered another issue @likangning93 . If a user passes a number of points, the removeDuplicates part filters that down to unique points. In some cases (in my case, for the first point you click on) this will filter down to just a single point. Which will cause this line to throw a developer error.

I think it would be okay for it to assume you pass at least two points (perhaps with a more descriptive error message), but since it internally filters down this list, I could pass two points, and one gets tossed away, and as a user I wouldn't know what's happening.

[mramato]

Actually, I just encountered another issue @likangning93 . If a user passes a number of points, the removeDuplicates part filters that down to unique points. In some cases (in my case, for the first point you click on) this will filter down to just a single point. Which will cause this line to throw a developer error.

I think it would be okay for it to assume you pass at least two points (perhaps with a more descriptive error message), but since it internally filters down this list, I could pass two points, and one gets tossed away, and as a user I wouldn't know what's happening.

Double check with other geometry, but I believe the official Cesium behavior here would be to simply not draw anything. Otherwise loading external datasets (which are almost always noisy and have issues like this) would be a giant pain for our users.