Drawing lines to the poles results in error

CesiumJS
1

Any reason why extending a polyline all the way to the poles throws this error? Am I doing something wrong here?

An error occurred while rendering. Rendering has stopped.
DeveloperError: Expected value to be greater than or equal to 0.0125, actual value was 0.012299641180522514

Increasing the latitude beyond 89.64 will crash the map. I would like the lines to extend all the way to 90.

Code:

const viewer = new Cesium.Viewer("cesiumContainer");

	const zoneWidth = 6;
	const lineColor = Cesium.Color.fromCssColorString("#888888").withAlpha(0.8);
	const lineWidth = 1;

	for (let zone = 1; zone <= 60; zone++)
	{
		const longitude = (zone - 1) * zoneWidth - 180;
        const latMax = 89.64;

		const positions = [
			Cesium.Cartesian3.fromDegrees(longitude, -latMax),
			Cesium.Cartesian3.fromDegrees(longitude, latMax),
		];


		viewer.entities.add({
			polyline: {
				positions: positions,
				width: lineWidth,
				material: lineColor,
				arcType: Cesium.ArcType.RHUMB,
			},
		});
	}

Sandcastle example

2

The limit of 0.0125 there indeed looks a bit arbitrary. But on a purely technical level, it can be justified: Imagine you had to draw a line on a globe, from the north pole to the south pole. Where would this line be? Note that even though you are giving a longitute in your code, all longitude values end up at the same position for the north- and south pole…

A reasonable (and simple) workaround might be to simply insert another point at the equator:

1 Like
3

Adding an extra point makes complete sense. Thanks.