# Synopsis

PDX_MSGT igeo_ExtractSurfaceIsoCurve(long option, MDA_PTR db_ptr_surf, double uv_parm, int model, double tolerance, int max_iters, MDA_PTR *db_ptr_curve)

# Purpose

Extract a surface iso-parametric curve from an IGES surface.

# Description

Given a valid IGES surface and a parameter value for an iso-parametric curve on the surface within the domain of the surface (0.0 <= uv_parm <= 1.0 normalized), returns the IGES curve extracted from the surface at the specified parametric location.

The IGES surface entity must be a valid IGES definition.

The extracted iso-parametric curve is exact for all basic surface types except the ruled surface and the offset surface. For the ruled surface, the interior surface curve in the U iso-parametric direction is a NURB curve which may be an approximation if one of the rail curves is an offset curve. For the offset surface, the iso-parametric curve is a NURB curve approximated to within tolerance tolerance of the true offset surface curve.

# Input

## option

### IGES_NOMATRIX

Do not apply entity matrix to data

### IGEO_VISOPARM

Get a V iso-parametric curve (uv_parm is a constant U parameter value).

### IGEO_UNNORM

Unnormalize the constant iso-parametric parameter value

## db_ptr_surf

The IGES surface entity database pointer

## uv_parm

The constant U or V parameter value

## model

The model to create the IGES extracted iso-parametric curve in

## tolerance

The tolerance for approximating an offset surface iso-parametric curve

## max_iters

The maximium number of iterations to test for convergence for approximation

# Output

## db_ptr_curve

The extract IGES curve entity database pointer

# Tolerances

          MODEL_SPACE_PNT_TOL
          ZERO_TOL
          COPLANAR_TOL
          PNT_PROJ_TOL
          ANGLE_TOL
          KNOT_TOL
          .fi

# Return

          IGEO_NOERR
          IGEO_INVALIDPARMVALUE
          Low level error return
          .fi