Plane_Align

181:Plane_Align (floor, ceiling, lineid)

Warning: This special is not fully supported by the UDMF map format. Certain parameters, noted below, have been made obsolete by the ability to directly specify properties within the linedef structure. These parameters should be set to 0 when using the UDMF format.

• floor: “1” slopes the floor on front side of the line; “2” slopes the floor on the back side.
• ceiling: Same as for floor, but for the ceiling plane, respectively.
• lineid: also sets this line's id if non-zero. Obsolete in UDMF.

Note: A value of 0 means no sloping is applied.

Aligns the plane of the floor and/or ceiling depending on the values floor and ceiling. For a more extensive look, check out slopes.

An example WAD can be found here.