Synopsis

PDX_MSGT gdx_EvalTorusDerivs(long option, T_GDX_TORUS *gdx_torus, int max_derivs, double uval, double vval, double derivs[][GDX_MAX_DEG+1][3])

Purpose

Evaluate point and derivatives on a GDX torus.

Description

At a given (u,v) parameter value, evaluate point and derivatives on the GDX torus entity. A max_derivs of 0 results in only the point on the torus being evaluated. The resulting derivatives are mixed partial derivatives in u and v. The GDX torus 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_torus

The GDX torus 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