Using perPositionHeight and ArcType.GEODESIC with PolygonGraphics

CesiumJS
1

I would like the define a polygon with vertex at different altitude, so I’m using perPositionHeight set to True. I’m defining large extent polygon so it’s important that the edges remains GEODESIC.

However, It seems like these option are mutuality exclusive.
For example:
With perPositionHeight = True

image
image1824×633 102 KB

And without

image
image1824×633 108 KB

I just want to confirm that I’m not making a mistake and to check if there is another way of going what I need.

Thanks!

2

Hi there,

The lines are still geodesic in your first example. The reason it’s clipping through the earth’s ellipsoid is because the polygon is not subdivded when creating a mesh. The subdivision is what is disabled when setting per-position height.

Is it possible to omit perPositionHeight and use a height of 8000.0 since all of the individual positions are at that height anyway?

3

Hi @Gabby_Getz

Thanks for the clarification. Yes I think your solution would work for our use case. Otherwise, is it possible to enable the subdivision in the per-position height setting?

Thanks

4

We deliberately skip subdivision for perPositionHeight as that is the point of that API property: to use the exact height on each position, and not make any further modification to make it fit the earth’s surface.

It would be possible to add a new property to enable behavior like you’re requesting, though I couldn’t guarantee the priority of when that would be implemented. Would you mind describing a little more background on your use case?

5

I was thinking about a case where the vertices of the polygon would be at different height. However, I realised that this could make it ambiguous in terms of fitting to earth’s surface.

1 Like