# Synopsis

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

# Purpose

Evaluate a derivatives on an IGES curve entity

# Description

At a given parameter value between 0.0 and 1.0 inclusive, evaluate derivatives on the IGES curve entity. The IGES curve entity must be a valid IGES definition. A max_deriv > the degree the curve will return zero derivative values in the derivs array. The IGES spline, composite and NURBS curve entities can be evaluated from the left or right (default).

# Input

## option

### IGES_NOMATRIX

Do not apply the IGES entities matrix to the data

### IGEO_FROMLEFT

Evaluate the derivates from the left

## db_ptr

The IGES curve entity database pointer

## matrix

The matrix to apply to the derivatives

## tval

The parameter value to evaluate (0.0 - 1.0)

## max_deriv

The maximum derivative required

# Output

## derivs

The 3D evaluted derivates

# Return

          IGEO_NOERR
          IGEO_ENTITYNOTCURVE
          Low level error return
          .fi