Normal of the planar face.
Namespace: Autodesk.Revit.DB
Assembly: RevitAPI (in RevitAPI.dll) Version: 25.0.0.0 (25.0.0.0)
public XYZ FaceNormal { get; }
This property is the “face normal” vector, and thus should return a vector consistently pointing out of the solid that this face is a boundary for (if it is a part of a solid).