# Synopsis

PDX_MSGT gdx_EvalParmSplDerivs(long option, T_GDX_SPLINE_CURVE *gdx_parm_spline, int max_deriv, double tval, double (*derivs)[3])

# Purpose

Evaluate derivatives on a GDX parametric spline.

# Description

For a given S parameter value, evaluates the derivatives on a GDX parametric spline. The parameter values are the unnormalized spline parameter values by default.

# Input

## option

### GDX_UNNORM

Unnormalize the parameter value

### GDX_FROMLEFT

Evaluate derivatives from the left side

## gdx_parm_spline

The GDX parametric spline data structure.

## max_deriv

The maximium deriviative desired

## tval

The parameter value

# Output

## derivs

The 3D deriviatives

# Return

          GDX_NOERR
          GDX_PARMOUTOFRANGE
          .fi