# Synopsis

PDX_MSGT gdx_EvalConeDerivs(long option, T_GDX_CONE *gdx_cone, int max_derivs, double uval, double vval, double derivs[][GDX_MAX_DEG+1][3])

# Purpose

Evaluate point and derivatives on a GDX cone.

# Description

At a given (u,v) parameter value, evaluate point and derivatives on the GDX cone entity. A max_derivs of 0 results in only the point on the cone being evaluated. The resulting derivatives are mixed partial derivatives in u and v. The GDX cone entity must be a valid GDX definition. Up to at most third derivatives will be computed. That is, if max_derivs > 3, zeros will be returned for all partial derivatives greater than third. The first derivs index represents derivatives with respect to v, and the second index, derivatives with respect to u. For example, derivs[1][0] is the first partial derivative with respect to v.

# Input

## option

### GDX_UNNORM

Unnormalize the parameter values

## gdx_cone

The GDX cone entity structure pointer

## max_derivs

The maximum derivative required

## uval

The surface u parameter value

## vval

The surface v parameter value

# Output

## derivs

The 3D mixed partial derivatives

# Return

          GDX_NOERR
          GDX_PARMOUTOFRANGE
          Low level error return
          .fi