Always passes the depth test.
Passes if fragment depth equals stored depth.
Passes if fragment depth is greater than stored depth.
Passes if fragment depth is greater than or equal to stored depth.
Passes if fragment depth is less than stored depth.
Passes if fragment depth is less than or equal to stored depth.
Never passes the depth test.
Passes if fragment depth does not equal stored depth.
How a Editor.Assets.PassInfo should determine its depth compared to others.