# Synopsis

PDX_MSGT gdx_ReverseSurface(long option, MDA_PTR gdx_surf_ptr)

# Purpose

Reverse the parametric directions of a GDX surface entity

# Description

Reverses either the u or v or both parametric directions of a GDX surface. Reversing just one of the directions reverses the directions of the surface normal vectors. Surfaces which can be reversed are:

.nf GDX_PLANE GDX_EXT_SURF GDX_REV_SURF GDX_RULED_SURF GDX_OFFSET_SURF GDX_NURB_SURF GDX_SPLINE_SURF GDX_RECT_TRIM_SURF

Some surfaces depend on sub-entities for their definition, and these subentities may be reversed or transformed. This is the case for: GDX_EXT_SURF : gen_curve is reversed if GDX_REVERSE_U is set. gen_curve is translated if GDX_REVERSE_V is set and v_parm > 0. GDX_RULED_SURF : both rail curves are reversed if GDX_REVERSE_U is set. The first rail curve is reversed if GDX_REVERSE_V and end_flag are set. GDX_REV_SURF : gen_curve is reversed if GDX_REVERSE_U is set. GDX_OFFSET_SURF : the relevant direction is reversed on the base surface. .fi

# Input

## option

### GDX_REVERSE_U

If set, the u direction will be reversed.

### GDX_REVERSE_V

If set, the v direction will be reversed. If neither option is set, nothing will happen; if both are set, both directions will be reversed.

## gdx_surf_ptr

The GDX surface entity database pointer.

# Return

          GDX_NOERR
          GDX_BADDATA
          GDX_ENTITYNOTSUPPORTED
          Low level error return
          .fi