1GACCUM_TRAN_MATRIX(3NCARG)       NCAR GRAPHICS      GACCUM_TRAN_MATRIX(3NCARG)
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NAME

6       gaccum_tran_matrix  (Accumulate  transformation  matrix) - Constructs a
7       GKS segment transformation matrix by starting with an  existing  matrix
8       and  composing  it  with  a shift vector, a rotation angle, and X and Y
9       scale factors to create a new transformation matrix.  The rotation  and
10       scaling are done with respect to a user-defined fixed point.
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SYNOPSIS

13       #include <ncarg/gks.h>
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15       void   gaccum_tran_matrix(const  Gtran_matrix  t_matrix,  const  Gpoint
16       *point, const Gvec *shift,  Gdouble  angle,  const  Gvec  *scale,  Gco‐
17       ord_switch coord_switch, Gtran_matrix tran_matrix);
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DESCRIPTION

20       t_matrix    (Gfloat, Input) - A 2x3 GKS transformation matrix.
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22       point.x     (Gfloat,  Input)  - X coordinate value for a fixed point to
23                   be used for the scaling and rotation parts  of  the  output
24                   transformation.   point.x is either in world coordinates or
25                   normalized device coordinates depending on the  setting  of
26                   the argument coord_switch described below.
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28       point.y     (Gfloat,  Input)  - Y coordinate value for a fixed point to
29                   be used for the scaling and rotation parts  of  the  output
30                   transformation.   point.y is either in world coordinates or
31                   normalized device coordinates depending on the  setting  of
32                   the argument coord_switch described below.
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34       shift.delta_x
35                   (Gfloat,  Input)  - The X component of a shift vector to be
36                   used for the scaling part  of  the  output  transformation.
37                   shift.delta_x  is either in world coordinates or normalized
38                   device coordinates depending on the setting of the argument
39                   coord_switch described below.
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41       shift.delta_y
42                   (Gfloat,  Input)  - The Y component of a shift vector to be
43                   used for the scaling part  of  the  output  transformation.
44                   shift.delta_y  is either in world coordinates or normalized
45                   device coordinates depending on the setting of the argument
46                   coord_switch described below.
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48       angle       (Input)  -  The  rotation angle, in radians, to be used for
49                   the rotation part of the output transformation.
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51       scale.delta_x
52                   (Gfloat, Input) - X coordinate scale factor to be  used  in
53                   the scaling part of the output transformation.
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55       scale.delta_y
56                   (Gfloat,  Input)  - Y coordinate scale factor to be used in
57                   the scaling part of the output transformation.
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59       coord_switch
60                   (Input) - A coordinate switch to indicate whether the  val‐
61                   ues for the arguments point and shift (described above) are
62                   in world  coordinates  or  normalized  device  coordinates.
63                   Possible values include:
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65                   GCOORD_WC
66                          World coordinates
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68                   GCOORD_NDC
69                          Normalized device coordinates
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71                   tran_matrix (Gfloat,  Output)  -  A 2x3 array that contains
72                               the GKS transformation matrix in  a  form  that
73                               can  be  used  as  input to other GKS functions
74                               such as gset_seg_tran.   This  matrix  is  con‐
75                               structed  by  composing  the scale, rotate, and
76                               shift input, described above, with the original
77                               input matrix t_matrix.
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USAGE

80       If world coordinates are used, the shift vector and the fixed point are
81       transformed by the current normalization transformation.
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83       The order in which the transformations are applied  is:  input  matrix,
84       scale, rotate, and shift.
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86       Elements  tran_matrix[0][2]  and  tran_matrix[1][2]  are  in normalized
87       device coordinates and the other elements of tran_matrix are unitless.
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89       gaccum_tran_matrix can be used to construct more general transformation
90       matrices  than  geval_tran_matrix.   The  most  common  usage  of  gac‐
91       cum_tran_matrix is to change the  order  in  which  the  operations  of
92       scale,   rotate,   and   shift   are   applied   (which   is  fixed  in
93       geval_tran_matrix).  The example below shows how to construct a  trans‐
94       formation matrix that shifts first and then rotates.
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EXAMPLE

97       Assuming  that the input matrix t_matrix is initially the identity, the
98       following code
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100             pi = 3.1415926;
101             point.x = point.y = 0.5;
102             shift.delta_x = 0.25;
103             shift.delta_y = 0.;
104             scale.delta_x = 1.0;
105             scale.delta_y = 1.0;
106             gaccum_tran_matrix(t_matrix,&point,&shift,0.,&scale,GCOORD_WC,tout);
107             for( i = 0; i < 2; i++ ) {
108                 for( j = 0; j < 3; j++ ) {
109                     t_matrix[i][j] = tout[i][j];
110                 }
111             }
112             shift.delta_x = 0.;
113             shift.delta_y = 0.;
114             gaccum_tran_matrix(t_matrix,&point,&shift,45.*pi/180.,&scale,GCOORD_WC,tout);
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116       would produce a transformation matrix  in  tout  that  would  shift  by
117       (.25,0.) first, and then rotate by 45 degrees.
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ACCESS

120       To  use  the  GKS  C-binding  routines,  load the ncarg_gks and ncarg_c
121       libraries.
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SEE ALSO

124       Online:    geval_tran_matrix(3NCARG),     gclose_seg(3NCARG),     gcre‐
125       ate_seg(3NCARG),         gcopy_seg_ws(3NCARG),        gdel_seg(3NCARG),
126       ginq_name_open_seg(3NCARG),                 ginq_set_seg_names(3NCARG),
127       gset_seg_tran(3NCARG), gks(3NCARG), ncarg_gks_cbind(3NCARG)
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129       Hardcopy:  User's  Guide for NCAR GKS-0A Graphics; NCAR Graphics Funda‐
130       mentals, UNIX Version
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133       Copyright (C) 1987-2009
134       University Corporation for Atmospheric Research
135       The use of this Software is governed by a License Agreement.
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139UNIX                              March 1993        GACCUM_TRAN_MATRIX(3NCARG)
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