# Synopsis

PDX_MSGT gdx_ExtractIsoCurve(long option, MDA_PTR gdx_db_ptr, int model, double uv, double tolerance, int max_iters, void *gdx_cur)

# Purpose

Extract an iso-parametric curve from a GDX surface.

# Description

This routine extracts an iso-parametric curve from a GDX surface. The GDX iso-parametric curve is the type of curve that represents the surface in the particular iso-parametric direction. The exception is for the interior of a ruled surface and the offset surface iso-parametric curves which are approximated as GDX NURB curves. The iso-parametric curve space the complete surface in the specified iso-parametric direction.

# Input

## option

### GDX_COMMIT

The entity creation option. If set, the GDX entity will be commited to the data base. Default is do not commit.

### GDX_UVALUE

If set, then uv is a u-value (isocurve is varying in v); otherwise, uv is a v-value (isocurve is varying in u).

## gdx_db_ptr

The input surface database pointer from which a curve is to be extracted.

## model

The GDX model to create the GDX iso curve in

## uv

A u- or v-value (see option). This defines which curve is to be extracted.

## tolerance

The tolerance used to approximate the offset surface iso-parametric curve.

## max_iters

The maximium iteration count to test for convergence for approximation

# Output

## gdx_cur

The extracted isocurve.

# Tolerances

          MODEL_SPACE_PNT_TOL
          COPLANAR_TOL
          ZERO_TOL
          KNOT_TOL
          PNT_PROJ_TOL
          ANGLE_TOL
          .fi

# Return

          GDX_NOERR
          Low level error return
          .fi