NAME¶
gactm - Accumulate (GKS) transformation matrix
DESCRIPTION¶
GACTM (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¶
CALL GACTM(MINP,X0,Y0,DX,DY,PHI,FX,FY,SW,MOUT)
C-BINDING 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¶
- MINP
- (Real, Input) - A 2x3 GKS transformation matrix.
- X0
- (Real, Input) - An X coordinate value for a fixed point to be used for the
scaling and rotation parts of the output transformation. X is either in
world coordinates or normalized device coordinates depending on the
setting of the argument SW described below.
- Y0
- (Real, Input) - A Y coordinate value for a fixed point to be used for the
scaling and rotation parts of the output transformation. Y is either in
world coordinates or normalized device coordinates depending on the
setting of the argument SW described below.
- DX
- (Real, Input) - The X component of a shift vector to be used for the
scaling part of the output transformation. DX is either in world
coordinates or normalized device coordinates depending on the setting of
the argument SW described below.
- DY
- (Real, Input) - The Y component of a shift vector to be used for the
scaling part of the output transformation. DY is either in world
coordinates or normalized device coordinates depending on the setting of
the argument SW described below.
- PHI
- (Real, Input) - The rotation angle, in radians, to be used for the
rotation part of the output transformation.
- FX
- (Real, Input) - An X coordinate scale factor to be used in the scaling
part of the output transformation.
- FY
- (Real, Input) - A Y coordinate scale factor to be used in the scaling part
of the output transformation.
- SW
- (Integer, Input) - A coordinate switch to indicate whether the values for
the arguments X0, Y0, DX, and DY (described above) are in world
coordinates or normalized device coordinates. SW=0 indicates world
coordinates and SW=1 indicates normalized device coordinates.
- MOUT
- (Real, 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 GSSGT.
This matrix is constructed by composing the scale, rotate, and shift
input, described above, with the original input matrix MINP.
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 MOUT(1,3) and MOUT(2,3) are in normalized device coordinates and the
other elements of MOUT are unitless.
GACTM can be used to construct more general transformation matrices than GEVTM.
The most common usage of GACTM is to change the order in which the operations
of scale, rotate, and shift are applied (which is fixed in GEVTM). The example
below shows how to construct a transformation matrix that shifts first and
then rotates.
EXAMPLE¶
Assuming that the input matrix TIN is initially the identity, the following code
PI = 3.1415926
CALL GACTM(TIN,.5,.5,.25,0.,0.,1.,1.,0,TOUT)
DO 20 I=1,2
DO 30 J=1,3
TIN(I,J) = TOUT(I,J)
30 CONTINUE
20 CONTINUE
CALL GACTM(TIN,.5,.5,0.,0.,45.*PI/180.,1.,1.,0,TOUT)
would produce a transformation matrix in TOUT that would shift by (.25,0.)
first, and then rotate by 45 degrees.
ACCESS¶
To use GKS routines, load the NCAR GKS-0A library ncarg_gks.
SEE ALSO¶
Online: gevtm, gclsg, gcrsg, gcsgwk, gdsg, gqopsg, gqsgus, gssgt.,
gaccum_tran_matrix
Hardcopy: "User's Guide for NCAR GKS-0A Graphics"
COPYRIGHT¶
Copyright (C) 1987-2009
University Corporation for Atmospheric Research
The use of this Software is governed by a License Agreement.