Merge remote-tracking branch 'origin/enhancement/free-camera-support'…

… into develop

src/WorldWindow.js

@@ -208,6 +208,8 @@ define([
              * @default [Camera]{@link Camera}
              */
             this.camera = new Camera();
+            // Initialize vertical field of view assuming that default angle value is horizontal
+            this.camera.fieldOfView *= this.viewport.height / this.viewport.width;
 
             /**
              * The controller used to manipulate the globe.
@@ -572,11 +574,17 @@ define([
          * @returns {LookAt} A reference to the result parameter.
          * @throws {ArgumentError} If the specified result object is null or undefined.
          */
-        WorldWindow.prototype.cameraAsLookAt = function (result, terrainPosition = this.pick([this.viewport.width / 2, this.viewport.height / 2]).terrainObject().position) {
+        WorldWindow.prototype.cameraAsLookAt = function (result, terrainPosition) {
             if (!result) {
                 throw new ArgumentError(
                     Logger.logMessage(Logger.LEVEL_SEVERE, "Camera", "getAsLookAt", "missingResult"));
             }
+            if (!terrainPosition) {
+                var terrainObject = this.pick([this.viewport.width / 2, this.viewport.height / 2]).terrainObject();
+                if (terrainObject) {
+                    terrainPosition = terrainObject.position;
+                }
+            }
 
             var globe = this.globe,
                 forwardRay = this.scratchRay,
@@ -812,6 +820,15 @@ define([
                 gl.canvas.width = width;
                 gl.canvas.height = height;
 
+                // Keep map scale by adopting field of view on view port resize
+                if (this.viewport.height !== 0) {
+                    try {
+                        this.camera.fieldOfView *= height / this.viewport.height;
+                    } catch (ignore: IllegalArgumentException) {
+                        // Keep original field of view in case new one does not fit requirements
+                    }
+                }
+
                 // Set the WebGL viewport to match the canvas drawing buffer size.
                 gl.viewport(0, 0, gl.drawingBufferWidth, gl.drawingBufferHeight);
                 this.viewport = new Rectangle(0, 0, gl.drawingBufferWidth, gl.drawingBufferHeight);