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SUBROUTINE FITVPT (XD, YD, ZD, NT, IPT, NL, IPL, PDD, ITI,
X XII, YII, ZII)
C$ (ALG526 - Internal Point Interpolation)
C$ This subroutine performs punctual interpolation or
C$ extrapolation, i.e., determines the Z value at a point.
C$ The input parameters are:
C$
C$ XD(*),
C$ YD(*),
C$ ZD(*)..........Arrays of dimension NDP containing the X, Y,
C$ and Z coordinates of the data points, where
C$ NDP is the number of the data points,
C$ NT.............Number of triangles,
C$ IPT............INTEGER array of dimension 3*NT containing
C$ the point numbers of the vertexes of the
C$ triangles,
C$ NL ............Number of border line segments,
C$ IPL............INTEGER array of dimension 3*NL containing
C$ the point numbers of the end points of the
C$ border line segments and their respective
C$ triangle numbers,
C$ PDD............Array of dimension 5*NDP containing the
C$ partial derivatives at the data points,
C$ ITI............Triangle number of the triangle in which
C$ lies the point for which interpolation is to
C$ be performed,
C$ XII,YII........X and Y coordinates of the point for which
C$ interpolation is to be performed.
C$
C$ The output parameter is
C$
C$ ZII............Interpolated Z value.
C$
C$ This routine incorporates the corrections published in
C$ Hiroshi Akima, "Remark on Algorithm 526", ACM Trans. Math.
C$ Software 5, No. 2, 242-243 (June 1979), and in Albrecht
C$ Preusser, "Remark on Algorithm 526", ACM Trans. Math.
C$ Software 11, No. 2, 186-187 (1985).
C$
C$ (02-AUG-85)