Fixed ray creation when the devicePixelRatio is not equls to 1. This PR has been tested on IE11, IE11 mobile, Chrome Android and Safari (iOS8).

Babylon/babylon.scene.js

@@ -1183,7 +1183,7 @@
             x = x / this._engine.getHardwareScalingLevel() - viewport.x;
             y = y / this._engine.getHardwareScalingLevel() - (this._engine.getRenderHeight() - viewport.y - viewport.height);
 
-            return BABYLON.Ray.CreateNew(x, y, viewport.width, viewport.height, world ? world : BABYLON.Matrix.Identity(), camera.getViewMatrix(), camera.getProjectionMatrix());
+            return BABYLON.Ray.CreateNew(x / window.devicePixelRatio, y / window.devicePixelRatio, viewport.width, viewport.height, world ? world : BABYLON.Matrix.Identity(), camera.getViewMatrix(), camera.getProjectionMatrix());
         };
 
         Scene.prototype._internalPick = function (rayFunction, predicate, fastCheck) {

Babylon/babylon.scene.ts

@@ -1269,7 +1269,7 @@
             x = x / this._engine.getHardwareScalingLevel() - viewport.x;
             y = y / this._engine.getHardwareScalingLevel() - (this._engine.getRenderHeight() - viewport.y - viewport.height);
 
-            return BABYLON.Ray.CreateNew(x, y, viewport.width, viewport.height, world ? world : BABYLON.Matrix.Identity(), camera.getViewMatrix(), camera.getProjectionMatrix());
+            return BABYLON.Ray.CreateNew(x / window.devicePixelRatio, y / window.devicePixelRatio, viewport.width, viewport.height, world ? world : BABYLON.Matrix.Identity(), camera.getViewMatrix(), camera.getProjectionMatrix());
         }
 
         private _internalPick(rayFunction: (world: Matrix) => Ray, predicate: (mesh: AbstractMesh) => boolean, fastCheck?: boolean): PickingInfo {