An axis that describes the direction along which the distances of objects are measured for the purpose of sorting.
This is the default axis used by the rendering pipeline for sorting in TransparencySortMode.CustomAxis mode for all Cameras including the SceneView's. You may override this for each invididual Camera by calling Camera.transparencySortAxis and Camera.transparencySortMode APIs.
Additional resources: TransparencySortMode enum, Camera.transparencySortAxis, Camera.transparencySortMode.