Fix issue in rhumb arc polylines

CHANGES.md

@@ -9,6 +9,7 @@
 ##### Fixes :wrench:
 
 - Fixed error with `WallGeoemtry` when there were adjacent positions with very close values [#8952](https://github.com/CesiumGS/cesium/pull/8952)
+- Fixed a bug where certain rhumb arc polylines would lead to a crash. [#8787](https://github.com/CesiumGS/cesium/pull/8787)
 
 ### 1.70.1 - 2020-06-10
 

Source/Core/PolylinePipeline.js

@@ -140,16 +140,15 @@ function generateCartesianRhumbArc(
   array,
   offset
 ) {
-  var first = ellipsoid.scaleToGeodeticSurface(p0, scaleFirst);
-  var last = ellipsoid.scaleToGeodeticSurface(p1, scaleLast);
-  var start = ellipsoid.cartesianToCartographic(first, carto1);
-  var end = ellipsoid.cartesianToCartographic(last, carto2);
-
+  var start = ellipsoid.cartesianToCartographic(p0, carto1);
+  var end = ellipsoid.cartesianToCartographic(p1, carto2);
   var numPoints = PolylinePipeline.numberOfPointsRhumbLine(
     start,
     end,
     granularity
   );
+  start.height = 0.0;
+  end.height = 0.0;
   var heights = subdivideHeights(numPoints, h0, h1);
 
   if (!ellipsoidRhumb.ellipsoid.equals(ellipsoid)) {

Specs/Core/PolylinePipelineSpec.js

@@ -177,4 +177,13 @@ describe("Core/PolylinePipeline", function () {
     expect(newPositions.length).toEqual(3);
     expect(newPositions).toEqual([0, 0, 1]);
   });
+
+  it("generateRhumbArc return values for each position", function () {
+    var newPositions = PolylinePipeline.generateRhumbArc({
+      positions: Cartesian3.fromDegreesArray([0, 0, 10, 0, 10, 5]),
+    });
+    for (let i = 0; i < newPositions.length; i++) {
+      expect(newPositions[i]).toBeDefined();
+    }
+  });
 });