Cache pickposition

CHANGES.md

@@ -32,6 +32,7 @@ Change Log
 * Fixed issues with imagerySplitPosition and the international date line in 2D mode. [#5151](https://github.com/AnalyticalGraphicsInc/cesium/pull/5151)
 * Fixed an issue with `TileBoundingBox` that caused the terrain to disappear in certain places [4032](https://github.com/AnalyticalGraphicsInc/cesium/issues/4032)
 * `QuadtreePrimitive` now uses `frameState.afterRender` to fire `tileLoadProgressEvent` [#3450](https://github.com/AnalyticalGraphicsInc/cesium/issues/3450)
+* `Scene.pickPosition` now caches results per frame to increase performance [#5117](https://github.com/AnalyticalGraphicsInc/cesium/issues/5117)
 
 ### 1.31 - 2017-03-01
 

Source/Scene/Scene.js

@@ -321,6 +321,8 @@ define([
         this._cameraStartFired = false;
         this._cameraMovedTime = undefined;
 
+        this._pickPositionCache = {};
+
         /**
          * Exceptions occurring in <code>render</code> are always caught in order to raise the
          * <code>renderError</code> event.  If this property is true, the error is rethrown
@@ -2523,6 +2525,8 @@ define([
     var scratchEyeTranslation = new Cartesian3();
 
     function render(scene, time) {
+        scene._pickPositionCache = {}; //clean <cache></cache>
+
         if (!defined(time)) {
             time = JulianDate.now();
         }
@@ -2616,6 +2620,7 @@ define([
      * @private
      */
     Scene.prototype.render = function(time) {
+
         try {
             render(this, time);
         } catch (error) {
@@ -3024,7 +3029,7 @@ define([
 
     var scratchPickPositionCartographic = new Cartographic();
 
-    /**
+     /**
      * Returns the cartesian position reconstructed from the depth buffer and window position.
      * <p>
      * The position reconstructed from the depth buffer in 2D may be slightly different from those
@@ -3043,6 +3048,16 @@ define([
      * @exception {DeveloperError} Picking from the depth buffer is not supported. Check pickPositionSupported.
      */
     Scene.prototype.pickPosition = function(windowPosition, result) {
+        var cacheKey;
+
+        if(defined(windowPosition)){
+            cacheKey = windowPosition.x + '-' + windowPosition.y;
+        }
+
+        if(defined(windowPosition) && this._pickPositionCache.hasOwnProperty(cacheKey)){
+            return Cartesian2.clone(this._pickPositionCache[cacheKey], result);
+        }
+
         result = this.pickPositionWorldCoordinates(windowPosition, result);
         if (defined(result) && this.mode !== SceneMode.SCENE3D) {
             Cartesian3.fromElements(result.y, result.z, result.x, result);
@@ -3053,6 +3068,9 @@ define([
             var cart = projection.unproject(result, scratchPickPositionCartographic);
             ellipsoid.cartographicToCartesian(cart, result);
         }
+
+        this._pickPositionCache[cacheKey] = Cartesian2.clone(result);
+
         return result;
     };
 

Specs/Scene/SceneSpec.js

@@ -838,6 +838,43 @@ defineSuite([
         });
     });
 
+    it('pickPosition caches results per frame',function(){
+        var s = createScene();
+        if (!s.pickPositionSupported) {
+            return;
+        }
+
+        var rectangle = Rectangle.fromDegrees(-100.0, 30.0, -90.0, 40.0);
+        s.camera.setView({ destination : rectangle });
+
+        var canvas = s.canvas;
+        var windowPosition = new Cartesian2(canvas.clientWidth / 2, canvas.clientHeight / 2);
+        spyOn(s, 'pickPositionWorldCoordinates').and.callThrough();
+
+        expect(s).toRenderAndCall(function() {
+            s.pickPosition(windowPosition);
+            expect(s.pickPositionWorldCoordinates).toHaveBeenCalled();
+
+            s.pickPosition(windowPosition);
+            expect(s.pickPositionWorldCoordinates.calls.count()).toEqual(1);
+
+            var rectanglePrimitive = createRectangle(rectangle);
+            rectanglePrimitive.appearance.material.uniforms.color = new Color(1.0, 0.0, 0.0, 1.0);
+
+            var primitives = s.primitives;
+            primitives.add(rectanglePrimitive);
+        });
+
+        expect(s).toRenderAndCall(function() {
+            s.pickPosition(windowPosition);
+            expect(s.pickPositionWorldCoordinates.calls.count()).toEqual(2);
+
+            s.pickPosition(windowPosition);
+            expect(s.pickPositionWorldCoordinates.calls.count()).toEqual(2);
+        });
+
+    });
+
     it('pickPosition throws without windowPosition', function() {
         expect(function() {
             scene.pickPosition();