NAME

       geval_tran_matrix - Connstruct GKS segment by evaluating a transform matrix

DESCRIPTION

       geval_tran_matrix  (Evaluate  transformation  matrix)  -  Constructs  a GKS segment transformation matrix
       starting from a given point, a shift vector, a rotation angle, and X and Y scale factors.

SYNOPSIS

       #include <ncarg/gks.h>

       void geval_tran_matrix(const Gpoint  *point,  const  Gvec  *shift,  Gdouble  angle,  const  Gvec  *scale,
       Gcoord_switch coord_switch, Gtran_matrix tran_matrix);

DESCRIPTION

       point.x     (Gfloat,  Input)  -  An  X  coordinate value for a fixed point to be used for the scaling and
                   rotation parts of the output transformation.  point.x  is  either  in  world  coordinates  or
                   normalized device coordinates depending on the setting of the argument coord_switch described
                   below.

       point.y     (Gfloat, Input) - A Y coordinate value for a fixed point to  be  used  for  the  scaling  and
                   rotation  parts  of  the  output  transformation.   point.y is either in world coordinates or
                   normalized device coordinates depending on the setting of the argument coord_switch described
                   below.

       shift.delta_x
                   (Gfloat,  Input)  -  The X component of a shift vector to be used for the scaling part of the
                   output transformation.  shift.delta_x is either in world  coordinates  or  normalized  device
                   coordinates depending on the setting of the argument coord_switch described below.

       shift.delta_y
                   (Gfloat,  Input)  -  The Y component of a shift vector to be used for the scaling part of the
                   output transformation.  shift.delta_y is either in world  coordinates  or  normalized  device
                   coordinates depending on the setting of the argument coord_switch described below.

       angle       (Input)  -  The  rotation  angle,  in radians, to be used for the rotation part of the output
                   transformation.

       scale.delta_x
                   (Gfloat Input) - An X coordinate scale factor to be used in the scaling part  of  the  output
                   transformation.

       scale.delta_y
                   (Gfloat  Input)  -  A  Y coordinate scale factor to be used in the scaling part of the output
                   transformation.

       coord_switch
                   (Input) - A coordinate switch to indicate whether the values  for  the  arguments  shift  and
                   scale  (described above) are in world coordinates or normalized device coordinates.  Possible
                   values include:

                   GCOORD_WC
                          World coordinates

                   GCOORD_NDC
                          Normalized device coordinates

                   tran_matrix (Gfloat, Output) - A 2x3 array that contains the GKS transformation matrix  in  a
                               form that can be used as input to other GKS functions such as gset_seg_tran.

USAGE

       If  world  coordinates  are  used,  the  shift  vector and the fixed point are transformed by the current
       normalization transformation.

       The order of the transformation operations as built into the output matrix is:  scale  (relative  to  the
       fixed point); rotate (relative to the fixed point; shift.

       Elements  tran_matrix[0][2]  and  tran_matrix[1][2]  are  in  normalized device coordinates and the other
       elements of tran_matrix are unitless.

EXAMPLE

       The following code

             pi = 3.1415926;
             point.x = point.y = 0.5;
             shift.delta_x = 0.25;
             shift.delta_y = 0.;
             scale.delta_x = 0.5;
             scale.delta_y = 1.5;
             geval_tran_matrix(&point,&shift,45.*pi/180.,&scale,GCOORD_WC,tm);

       would produce a transformation matrix in tm that would: scale the  X  coordinates  by  .5,  scale  the  Y
       coordinates by 1.5 (relative to the fixed point of (.5,.5) ); rotate by 45 degrees (relative to the fixed
       point (.5,.5) ); and shift by .25 in X and 0. in Y.  The input values  for  the  fixed  point  and  shift
       vector are in world coordintes.

ACCESS

       To use the GKS C-binding routines, load the ncarg_gks and ncarg_c libraries.

SEE ALSO

       Online:   gaccum_tran_matrix(3NCARG),   gclose_seg(3NCARG),   gcreate_seg(3NCARG),  gcopy_seg_ws(3NCARG),
       gdel_seg(3NCARG),    ginq_name_open_seg(3NCARG),    ginq_set_seg_names(3NCARG),    gset_seg_tran(3NCARG),
       gks(3NCARG), ncarg_gks_cbind(3NCARG)

       Hardcopy: User's Guide for NCAR GKS-0A Graphics; NCAR Graphics Fundamentals, UNIX Version

COPYRIGHT

       Copyright (C) 1987-2009
       University Corporation for Atmospheric Research
       The use of this Software is governed by a License Agreement.