If there is a distance in height between plane measured by specified Plane Tool and area to measure obstruction, set the distance here. By setting a value to the [Plane Height Offset], the plane to decide obstruction is shifted by the value from plane measured by specified Plane Tool in normal direction to the plane. Set positive value if the area to measure obstruction is on the normal vector direction of plane measurement by specified Plane Tool, set negative value that is on the inverse direction.