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.