use devicePosition instead of global position when setting eye position for webVRCamera

src/Materials/materialHelper.ts

@@ -13,6 +13,7 @@ import { Light } from "../Lights/light";
 import { UniformBuffer } from "./uniformBuffer";
 import { Effect, EffectFallbacks, EffectCreationOptions } from "./effect";
 import { BaseTexture } from "../Materials/Textures/baseTexture";
+import { WebVRFreeCamera } from '../Cameras/VR/webVRCamera';
 
 /**
  * "Static Class" containing the most commonly used helper while dealing with material for
@@ -34,7 +35,12 @@ export class MaterialHelper {
             effect.setVector3("vEyePosition", scene._forcedViewPosition);
             return;
         }
-        effect.setVector3("vEyePosition", scene._mirroredCameraPosition ? scene._mirroredCameraPosition : scene.activeCamera!.globalPosition);
+        var globalPosition = scene.activeCamera!.globalPosition;
+        if (!globalPosition) {
+            // Use WebVRFreecamera's device position as global position is not it's actual position in babylon space
+            globalPosition = (scene.activeCamera! as WebVRFreeCamera).devicePosition;
+        }
+        effect.setVector3("vEyePosition", scene._mirroredCameraPosition ? scene._mirroredCameraPosition : globalPosition);
     }
 
     /**