# Synopsis

PDX_MSGT gdx_SurfaceToReverseSurface(long option, MDA_PTR gdx_surf_ptr, MDA_PTR *gdx_reverse_surf_ptr)

# Purpose

Reverse the prametric direction of a surface

# 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. The reversal of all surfaces changes the parameterization of the surface. All parm curves associated to the surface should be deleted and regenerated if needed. The analytical surfaces, GDX_CONE, GDX_CYLINDER, GDX_SPHERE, GDX_TORUS, will be converted into GDX_REV_SURFACES and then reversed. This may result in U or V being reversed. 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 GDX_CONE GDX_CYLINDER GDX_SPHERE GDX_TORUS .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.

# Output

## gdx_reverse_surf_ptr

The DB pointer of the resulting reversed surface

# Return

          GDX_NOERR
          GDX_BADDATA
          GDX_ENTITYNOTSUPPORTED
          Low level error return
          .fi