(* COPYRIGHT 1993 DCC-IMECC, Universidade Estadual de Campinas *)
INTERFACE VTGR1Extra;

FROM VTGR1 IMPORT LocalState;

TYPE
  Derivatives = RECORD f, fx, fy, fz, fxy, fxz, fyz, fxx, fyy, fzz: REAL END;
  (*
    Value and spatial derivatives of a trivariate function at a point. *)
  
PROCEDURE ComputeDerivatives(READONLY ts: LocalState; VAR ds: Derivatives);
  (*
    Computes the spatial derivatives of a texture at a grid point,
    given the values in the point's neighborhood. *)

END VTGR1Extra.