Synopsis

PDX_MSGT gdx_EvalRuledSurfDerivs(long option, T_GDX_RULED_SURF *gdx_ruled_surf, int max_derivs, double uval, double vval, double derivs[][GDX_MAX_DEG + 1][3])

Purpose

Evaluate derivatives on a GDX ruled surface

Description

At a given U and V parameter value, evaluate derivatives on the GDX ruled surface entity. A max_derivs of 0 is equivalent to evaluating a point on the GDX ruled surface entity. The resulting derivatives are mixed partial derivatives in U and V. The GDX ruled surface entity must be a valid GDX definition. The derivatives can be evaluated from the left or right. A max_derivs > 3 returns zero derivative values. The first derivs index are the V derivatives with respect to U (ie derivs[1][0] is the V tangent derivative).

Input

option

GDX_FROMLEFT

Evaluate derivatives from the left

gdx_ruled_surf

The GDX ruled surface entity structure pointer

max_derivs

The maximium derivative required

uval

The surface U parameter value to evaluate

vval

The surface V parameter value to evaluate

Output

derivs

The 3D mixed partial derivatives

Return

      GDX_NOERR
      GDX_PARMOUTOFRANGE
      GDX_NOMEMORY
      Low level error return
      .fi