Merge pull request #9316 from littlemurph/EllipsoidGeodsic_SurfaceDis…

…tance_NaN Ellipsoid geodsic surface distance nan
CesiumGS · Feb 3, 2021 · 4c7fb7c · 4c7fb7c
2 parents ca8b918 + 2b786f6
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diff --git a/CHANGES.md b/CHANGES.md
@@ -1,5 +1,11 @@
 # Change Log
 
+### 1.79 - 2021-03-01
+
+##### Fixes :wrench:
+
+- Fixed an issue where certain inputs to EllipsoidGeodesic would result in a surfaceDistance of NaN. [#9316](https://github.com/CesiumGS/cesium/pull/9316)
+
 ### 1.78 - 2021-02-01
 
 ##### Additions :tada:

diff --git a/CONTRIBUTORS.md b/CONTRIBUTORS.md
@@ -283,3 +283,4 @@ See [CONTRIBUTING.md](CONTRIBUTING.md) for details on how to contribute to Cesiu
 - [Victor Turansky](https://github.com/turansky)
 - [Will Jadkowski](https://github.com/willjad)
 - [Mac Clayton](https://github.com/mclayton7)
+- [Ben Murphy](https://github.com/littlemurph)
diff --git a/Source/Core/EllipsoidGeodesic.js b/Source/Core/EllipsoidGeodesic.js
@@ -171,7 +171,7 @@ function vincentyInverseFormula(
 
     cosineTwiceSigmaMidpoint = cosineSigma - (2.0 * ss) / cosineSquaredAlpha;
 
-    if (isNaN(cosineTwiceSigmaMidpoint)) {
+    if (!isFinite(cosineTwiceSigmaMidpoint)) {
       cosineTwiceSigmaMidpoint = 0.0;
     }
 

diff --git a/Specs/Core/EllipsoidGeodesicSpec.js b/Specs/Core/EllipsoidGeodesicSpec.js
@@ -121,6 +121,19 @@ describe("Core/EllipsoidGeodesic", function () {
     );
   });
 
+  it("computes distance very close to equator", function () {
+    // See https://github.com/CesiumGS/cesium/issues/9248
+
+    var ellipsoid = new Ellipsoid(6, 6, 3);
+
+    var start = new Cartographic(-CesiumMath.EPSILON10, CesiumMath.EPSILON10);
+
+    var end = new Cartographic(+CesiumMath.EPSILON10, CesiumMath.EPSILON10);
+
+    var geodesic = new EllipsoidGeodesic(start, end, ellipsoid);
+    expect(geodesic.surfaceDistance).not.toBeNaN();
+  });
+
   it("computes distance at meridian", function () {
     var ellipsoid = new Ellipsoid(6, 6, 6);
     var fifteenDegrees = Math.PI / 12;