Drawing Arc line

Hi,

Trying this again.
I am a cesium newbie and I would like to draw an arc line from point A (lng/lat) to point B (lng/lat). I tried using the poly line but it seems to be a flat line which doesn't account for the 3D curvature. Does cesium contain a draw arc function which I can use to draw the arc line? Thank you for your help.

Hi,

We have this on the roadmap to do quite soon since we also want it for walls.

In the meantime, there is a small C# function that you can port to JavaScript to create the curve, and then pass all the positions to the Polyline. See this discussion.

Patrick

Hi,
Thank you for the information.
For now, I solved it modifying a function on an earlier thread. My function below.

var earth = Cesium.Ellipsoid.WGS84;

// start and end points on the surface of the earth

var startPoint = earth.cartographicToCartesian(Cesium.Cartographic.fromDegrees(pointA[0][0], pointA[0][1], 0.0));

var endPoint = earth.cartographicToCartesian(Cesium.Cartographic.fromDegrees(pointB[0][0], pointB[0][1], 0.0));

// determine the midpoint (point will be inside the earth)

// move the midpoint to the surface of the earth

earth.scaleToGeodeticSurface(midpointCartesian);

// add some altitude if you want (1000 km in this case)

var midpointCartographic = earth.cartesianToCartographic(midpointCartesian);

midpointCartographic.height = 1000000;

midpointCartesian = earth.cartographicToCartesian(midpointCartographic);

// create a hermite spline that goes through these three points

var hermiteSpline = new Cesium.HermiteSpline( [

{point: startPoint, time: 0.0},

{point: midpointCartesian, time: 0.5},

{point: endPoint, time: 1.0}

]);

// create a 20 point polyline that follows the spline

var polylinePoints = ;

for(var i=0; i<20; ++i) {

polylinePoints.push(hermiteSpline.evaluate(i/20));

}

var polylineCollection = new Cesium.PolylineCollection();

polyline.setPositions(polylinePoints);

var primitives = widget.scene.getPrimitives();

}

I feel the most important is add the accurate altitude values from terrain. So the new polyline will exactly on the top of surface. Is there a way to pull the height values for each coordinates of the polyline, like drape the polyline on terrain? Thanks.

See the Sample Everest Height example in the Sandcastle terrain example. This uses Cesium.sampleTerrain to get the altitudes, which is a reasonable choice for now until we implement polylines on terrain perhaps later this year.

Patrick

I know this is much later, but did this roadmapped feature ever get realized?

Polylines added via the Entity API curve to the globe by default. You can see an example here: http://cesiumjs.org/Cesium/Apps/Sandcastle/index.html?src=Polyline.html&label=Geometries
We do not yet have support for polylines on terrain.

-Hannah