# Synopsis

PDX_MSGT gdx_EvalCurveDerivs(long option, MDA_PTR db_ptr, double tval, int max_deriv, double (*derivs)[3])

# Purpose

Evaluate derivatives on a GDX curve entity

# Description

At a given parameter value in the domain of the GDX curve by default, evaluate derivatives on the GDX curve entity. A @max_deriv > the maximum derivative supported for the GDX curve will return zero derivative values in the derivs array. The GDX curve can be evaluated parametrically from the low U or high U parameter values (high U is the default). supported for evaluation are:

.RS 4 GDX_ARC .RE .RS 4 GDX_COMP_CURVE .RE .RS 4 GDX_CONIC .RE .RS 4 GDX_NURB_CURVE .RE .RS 4 GDX_OFFSET_CURVE .RE .RS 4 GDX_POLYLINE .RE .RS 4 GDX_SPLINE_CURVE .RE .RS 4 GDX_TRIM_CURVE .RE

# Input

## option

### GDX_UNNORM

Unnormalize the parameter value

### GDX_FROM_LOW_U

Evaluate the derivatives from the low U parameter values.

## db_ptr

The GDX curve entity database derivser

## tval

The parameter value to evaluate in the parametric domain of the GDX curve

## max_deriv

The maximum derivative required

# Output

## derivs

The 3D evaluated derivatives

# Return

          GDX_NOERR
          GDX_ENTITYNOTCURVE
          Low level error return
          .fi