From VWW Wiki
Details to keep in mind when exporting Unity Scenes
- Ensure that your project settings have all necessary graphics pipelines selected and that you are in the Linear color space.
- Make sure all scene items are under a GameObject called _World
- If your scene has any realtime reflection probes make sure they are set to Refresh Mode: By Scripting. They should also be grouped under a GameObject called Reflection_GRP They will be updated automatically every 60 seconds.
- Make sure your scenes do not contain any Scripts (MonoBehaviours) or Cameras.
- Mark anything that will not move or change size/rotation as Static
- Use mesh colliders sparingly, it is better to create complex colliders out of many boxes/spheres instead of using a Mesh Collider.
- Be sure to use the latest Scene Export File:ExportScenes.cs script.