Type of sorting to use while rendering.
By default, perspective cameras sort objects based on distance from camera position
to the object center; and orthographic cameras sort based on distance along the view direction.
If you're making a 2D game with a perspective camera, you might want to use DistanceMetric.Orthographic
sort mode so that objects are sorted based on distance along the camera's view direction.
| Perspective | Perspective sorting mode. |
| Orthographic | Orthographic sorting mode. |
| CustomAxis | Sort objects based on distance along a custom axis. |