One raw entry in an explicit mipmap chain, including level zero. Cube chains contain six entries for every level.
Optional
Required for 3D and 2D-array levels. Array layers remain constant across levels.
Required only for cube maps. Cube chains contain six consecutive entries per level in canonical face order (+X, -X, +Y, -Y, +Z, -Z).
One raw entry in an explicit mipmap chain, including level zero. Cube chains contain six entries for every level.