# Synopsis

PDX_MSGT gdx_EvalOffsetCurveDerivs(long option, T_GDX_OFFSET_CURVE *gdx_oc, double tval, int max_derivs, double (*derivs)[3])

# Purpose

Evaluate derivatives on a GDX offset curve

# Description

At a given parameter value and the GDX offset curve definition, evaluate derivatives on the GDX offset curve entity. A max_derivs of 0 is equivalent to evaluating a point on the GDX offset curve entity. The GDX offset curve entity must be a valid GDX definition. A max_derivs > 3 returns zero derivative values.

# Input

## option

### GDX_FROMLEFT

Evaluate the derivatives from the left

## gdx_oc

The GDX offset curve entity data structure

## tval

The parameter value to evaluate

## max_derivs

The maximium derivative required

# Output

## derivs

The max_derivs 3D derivatives

# Return

          GDX_NOERR
          Low level error return
          .fi