# Synopsis

PDX_MSGT gdx_ConvertExtSurfToNurbSurf(long option, MDA_PTR db_ptr, int model, double tolerance, int max_iters, void *gdx_nurb_surf)

# Purpose

Convert a GDX extruded surface to a GDX NURB Surface

# Description

Converts a GDX extruded surface entity to a GDX NURB Surface entity.

The base GDX directrix curve is converted to the cooresponding NURBS definition and the resultant NURBS curve is used to define the NURBS surface.

The tolerance and max_iters values apply to the subordinate directrix curve that are converted to a NURBS curve. In addition the tolerance applies for closure test.

If a conversion error occurs any data created during the conversion is deleted and no GDX NURB Surface is created. The NURBS curve entity used to create the NURBS surface is deleted.

The GDX extruded surface entity and the subordinate directrix entity must be valid GDX definitions.

The conversion is geometrically exact if the conversion of the directrix curve is exact to the precision of the input data and to machine precision. If the conversion of the directrix curve is approximate, then the conversion of the GDX extruded surface is approximate.

# Input

## option

### GDX_COMMIT

Commit the GDX NURB Surface to the database

## db_ptr

The valid GDX extruded surface entity database pointer

## model

The model to create the GDX NURB Surface in

## tolerance

The tolerance for the directrix curve to NURBS conversion

## max_iters

The maximium iterations for convergence test for directrix curve to NURBS conversion

# Output

## gdx_nurb_surf

The GDX NURB Surface entity database pointer or the structure pointer

# Tolerances

          PNT_PROJ_TOL
          ANGLE_TOL
          ZERO_TOL
          .fi

# Return

          GDX_NOERR
          GDX_INVALIDMODEL
          GDX_INVALIDENTITYTYPE
          Low level error return
          .fi