Provided by: libncarg-dev_6.1.2-7_amd64 
NAME
GACCUM_TRAN_MATRIX - Accumulate transformation matrix
DESCRIPTION
gaccum_tran_matrix (Accumulate transformation matrix) - Constructs a GKS segment
transformation matrix by starting with an existing matrix and composing it with a shift
vector, a rotation angle, and X and Y scale factors to create a new transformation matrix.
The rotation and scaling are done with respect to a user-defined fixed point.
SYNOPSIS
#include <ncarg/gks.h>
void gaccum_tran_matrix(const Gtran_matrix t_matrix, const Gpoint *point, const Gvec
*shift, Gdouble angle, const Gvec *scale, Gcoord_switch coord_switch, Gtran_matrix
tran_matrix);
DESCRIPTION
t_matrix (Gfloat, Input) - A 2x3 GKS transformation matrix.
point.x (Gfloat, Input) - 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) - 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) - X coordinate scale factor to be used in the scaling part of
the output transformation.
scale.delta_y
(Gfloat, Input) - 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
point and shift (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. This matrix is constructed
by composing the scale, rotate, and shift input, described above,
with the original input matrix t_matrix.
USAGE
If world coordinates are used, the shift vector and the fixed point are transformed by the
current normalization transformation.
The order in which the transformations are applied is: input matrix, scale, rotate, and
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.
gaccum_tran_matrix can be used to construct more general transformation matrices than
geval_tran_matrix. The most common usage of gaccum_tran_matrix is to change the order in
which the operations of scale, rotate, and shift are applied (which is fixed in
geval_tran_matrix). The example below shows how to construct a transformation matrix that
shifts first and then rotates.
EXAMPLE
Assuming that the input matrix t_matrix is initially the identity, the following code
pi = 3.1415926;
point.x = point.y = 0.5;
shift.delta_x = 0.25;
shift.delta_y = 0.;
scale.delta_x = 1.0;
scale.delta_y = 1.0;
gaccum_tran_matrix(t_matrix,&point,&shift,0.,&scale,GCOORD_WC,tout);
for( i = 0; i < 2; i++ ) {
for( j = 0; j < 3; j++ ) {
t_matrix[i][j] = tout[i][j];
}
}
shift.delta_x = 0.;
shift.delta_y = 0.;
gaccum_tran_matrix(t_matrix,&point,&shift,45.*pi/180.,&scale,GCOORD_WC,tout);
would produce a transformation matrix in tout that would shift by (.25,0.) first, and then
rotate by 45 degrees.
ACCESS
To use the GKS C-binding routines, load the ncarg_gks and ncarg_c libraries.
SEE ALSO
Online: geval_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.