Factored surfaceNormalAtPoint into GeographicProjection and modified Globe accordingly.

src/globe/Globe.js

@@ -388,6 +388,12 @@ define([
                     "missingResult"));
             }
 
+            // For backwards compatibility, check whether the projection defines a surfaceNormalAtPoint function
+            // before calling it. If it's not available, use the old code to compute the normal.
+            if (this.projection.surfaceNormalAtPoint) {
+                return this.projection.surfaceNormalAtPoint(this, x, y, z, result);
+            }
+
             if (this.is2D()) {
                 result[0] = 0;
                 result[1] = 0;

src/projections/GeographicProjection.js

@@ -199,5 +199,30 @@ define([
             return result;
         };
 
+        /**
+         * Computes the Cartesian surface normal vector at a specified Cartesian point.
+         *
+         * @param {Globe} globe The globe this projection is applied to.
+         * @param {number} x The X component of the Cartesian point.
+         * @param {number} y The Y component of the Cartesian point.
+         * @param {number} z The Z component of the Cartesian point.
+         * @param {Vec3} result A variable in which to return the computed vector.
+         *
+         * @returns{Vec3} The specified result argument containing the computed vector.
+         * @throws {ArgumentError} If either the specified globe or result argument is null or undefined.
+         */
+        GeographicProjection.prototype.surfaceNormalAtPoint = function (globe, x, y, z, result) {
+            if (!result) {
+                throw new ArgumentError(Logger.logMessage(Logger.LEVEL_SEVERE, "GeographicProjection", "surfaceNormalAtPoint",
+                    "missingResult"));
+            }
+
+            result[0] = 0;
+            result[1] = 0;
+            result[2] = 1;
+
+            return result;
+        };
+
         return GeographicProjection;
     });

src/projections/ProjectionWgs84.js

@@ -272,5 +272,21 @@ define([
             return this.northTangentAtLocation(globe, this.scratchPosition.latitude, this.scratchPosition.longitude, result);
         };
 
+        ProjectionWgs84.prototype.surfaceNormalAtPoint = function (globe, x, y, z, result) {
+            if (!globe) {
+                throw new ArgumentError(Logger.logMessage(Logger.LEVEL_SEVERE, "ProjectionWgs84",
+                    "surfaceNormalAtPoint", "missingGlobe"));
+            }
+
+            var eSquared = globe.equatorialRadius * globe.equatorialRadius,
+                polSquared = globe.polarRadius * globe.polarRadius;
+
+            result[0] = x / eSquared;
+            result[1] = y / polSquared;
+            result[2] = z / eSquared;
+
+            return result.normalize();
+        };
+
         return ProjectionWgs84;
     });