1VELVCT(3NCARG) NCAR GRAPHICS VELVCT(3NCARG)
2
6 VELVCT - Plots a vector field, given two 2-dimensional vector component
7 arrays, U and V. You may control certain characteristics of the plot by
8 adjusting the values given to the input arguments. Other less
9 frequently changed characteristics may be affected by modifying VELDAT,
10 the BLOCK DATA routine that initializes members of the common blocks
11 VEC1 and VEC2. In addition, depending on the value given to the
12 compatibility parameter, CPM, you may set other options by calling
13 VVSETC, VVSETI, or VVSETR to modify internal parameters.
14
16 CALL VELVCT (U,LU,V,LV,M,N,FLO,HI,NSET,LENGTH,ISPV,SPV)
17
19 VELVCT is obsolete, and is supported only to provide compatibility with
20 old NCAR Graphics codes. However, the compatibility mode parameter,
21 CPM, offers a number of options to help ease the the transition to the
22 new version of the utility. When writing new code you are encouraged
23 not to use this entry point, since it provides less capability than the
24 standard Vectors interface, and may eventually be phased out.
25
27 #include <ncarg/ncargC.h>
28 void c_velvct(float *u, int lu, float *v, int lv, int m,
30 int n, float flo, float hi, int nset,
31 int length, int ispv, float *spv)
32
34 U (REAL 2-dimensional array, dimensioned LU x n: n >= N,
35 input): By default, assumed to contain the first
36 dimensional Cartesian components of the vector field.
37 However, if PLR is non-zero, it is treated as containing
38 the vector magnitudes.
39 LU (INTEGER, input): Actual value of the first dimension of
41 array U.
42 V (REAL 2-dimensional array, dimensioned LV x n: n >= N,
44 input): By default, assumed to contain the second
45 dimensional Cartesian components of the vector field.
46 However, if PLR is non-zero, it is treated as containing
47 the vector angles.
48 LV LV (INTEGER, input): Actual value of the first dimension of
50 array V.
51 M (INTEGER, input): Number of contiguous elements along the
53 first dimensional axis containing data to be processed in
54 each of the arrays, U and V.
55 N (INTEGER, input): Number of contiguous elements along the
57 second dimensional axis containing data to be processed in
58 each of the arrays, U and V.
59 FLO (REAL, input): Minimum vector magnitude allowed to be
61 displayed in the plot.
62 HI (REAL, input): Maximum vector magnitude allowed to be
64 displayed in the plot. If set to 0.0 there is no upper
65 limit imposed.
66 NSET (INTEGER, input): Flag that controls how and when the SET
68 call is invoked. If NSET is 0, VELVCT makes a SET call to
69 establish a standard viewport and window boundaries
70 coincident with the array coordinate boundaries. PERIM is
71 called to draw a border. If NSET is greater than zero,
72 VELVCT does not call SET or PERIM. If NSET is less than
73 zero, VELVCT calls SET to establish window boundaries
74 coincident with the array grid coordinate boundaries but
75 does not modify the viewport or call PERIM. Unlike the
76 VVINIT/VVECTR interface, when VELVCT does a SET call, it
77 always restores the original coordinate system state before
78 returning.
79 LENGTH (INTEGER, input): The length in plotter address units
81 (PAUs) used to render the vector with the greatest
82 magnitude that is eligible for plotting. A vector is
83 eligible for plotting if it is less than or equal to the
84 value of HI, unless HI is 0.0 in which case all vectors are
85 eligible. If LENGTH is set to 0.0, the length selected is
86 one half the diagonal length of a grid cell assuming a
87 linear mapping of the grid coordinate space into the
88 viewport.
89 ISPV (INTEGER, input): Flag to control the special value
91 feature. 0 means that the feature is not in use. 1 means
92 that if the value of U(I,J)=SPV(1) the vector will not be
93 plotted. 2 means that if the value of V(I,J)=SPV(2) the
94 vector will not be plotted. 3 means that if either
95 U(I,J)=SPV(1) or V(I,J)=SPV(2) then the vector will not be
96 plotted. 4 means that if U(I,J)=SPV(1) and V(I,J)=SPV(2),
97 the vector will not be plotted.
98 SPV (REAL array, dimensioned 2, input): An array of length 2
100 which gives the value in the U array and the value in the V
101 array which denote special values. This argument is ignored
102 if ISPV=0. The default values are 1.0E12.
103
105 The C-binding argument descriptions are the same as the FORTRAN
106 argument descriptions with the following exceptions:
107 lu The second dimension of u in the calling program.
110 lv The second dimension of v in the calling program.
112 m Number of contiguous elements along the second dimensional
114 axis containing data to be processed in each of the arrays,
115 u and v.
116 n Number of contiguous elements along the first dimensional
118 axis containing data to be processed in each of the arrays,
119 u and v.
120
122 Beginning with version 3.2 of NCAR Graphics, the VELVCT entry point has
123 been recoded as a front end to the VVINIT/VVECTR interface to Vectors.
124 The compatibility mode parameter, CPM, controls the degree to which a
125 call to the Version 3.2 VELVCT emulates the older call. Appropriate
126 settings of CPM can separately address each of the following three
127 questions regarding the level of emulation:
128 · Should FX, FY, MXF, and MYF rather than the Version 3.2 mapping
130 routines perform the mapping to user coordinates?
131 · Should the input arguments FLO, HI, NSET, LENGTH, ISPV, SPV
133 override the current values of the corresponding Vectors'
134 internal parameters?
135 · Should the values contained in the common blocks VEC1 and VEC2
137 override the current values of corresponding Vectors' internal
138 parameters?
139 Given the default value of CPM, all these questions are answered in the
141 affirmative, and a call to VELVCT gives a reasonably faithful emulation
142 of the older version's behavior.
143 However, even in this case, it is possible to use the parameter setting
145 routines to control the behavior of features that have no counterpart
146 in the older version of VELVCT, as long as the feature is accessible
147 without calling the new interface. For instance, you could control the
148 vector linewidth by setting the LWD parameter, although you could not
149 draw vectors masked to an area map because doing so requires direct
150 invocation of VVECTR
151 The following two tables show how the VELVCT input arguments and
153 VEC1/VEC2 common block members map into internal parameters currently
154 supported by Vectors. (Consult the vectors_params man page for
155 descriptions of the internal parameters.)
156 Input Argument Internal Parameter
158 FLO VLC (VLC is set to -FLO if FLO is
160 positive, 0.0 otherwise)
161 HI VHC (VHC is set to -HI if HI is positive,
163 0.0 otherwise)
164 NSET SET (NSET = 0 is approximately equivalent
166 to SET = 1)
167 LENGTH VRL (LENGTH in Plotter Address Units is
169 converted to VRL as a fraction of the
170 viewport width)
171 ISPV SVF
173 SPV(1) USV
175 SPV(2) VSV
177 Common Block Member Internal Parameter
180 EXT VPS
182 ICTRFG VPO
184 ILAB LBL
186 IOFFD DPF
188 RMN AMN (RMN in metacode coordinates is
190 converted to AMN as a fraction of the
191 viewport width)
192 RMX AMX (RMX in metacode coordinates is
194 converted to AMX as a fraction of the
195 viewport width)
196 SIZE LBS (Character size in metacode
198 coordinates is converted to LBS as a
199 fraction of viewport width)
200 INCX XIN
202 INCY YIN
204 - MNT (When common blocks VEC1 and VEC2
206 override parameter settings, MNT is always
207 set to " ", indicating that the minimum
208 vector text block is not to be displayed.)
209 IOFFM MXT (If IOFFM is non-zero, MXT is set to "
211 ", indicating that the maximum text block
212 is not to be displayed. Otherwise MXT is
213 set to the string "MAXIMUM VECTOR")
214 IOFFM MXX (If IOFFM is 0, MXX is set to a
216 computed value that, as a fraction of the
217 viewport width, specifies a point 0.05 in
218 NDC left of the right hand edge of the
219 plotter frame.)
220 IOFFM MXY (If IOFFM is 0, MXY is set to a
222 computed value that, as a fraction of the
223 viewport height, specifies a point 0.005
224 in NDC up from the bottom edge of the
225 plotter frame.)
226 IOFFM MXP (If IOFFM is 0, MXP is set to -2,
228 indicating that the text block should be
229 lower-right justified.
230
232 the older implementation in that it now uses high-quality text.
233
235 Use the ncargex command to see the following relevant example: stex02,
236 tvelvc.
237
239 To use VELVCT or c_velvct, load the NCAR Graphics libraries ncarg,
240 ncarg_gks, and ncarg_c, preferably in that order.
241
243 Online: vectors, vectors_params, fx, vvectr, vvgetc, vvgeti, vvgetr,
244 vvinit, vvrset, vvsetc, vvseti, vvsetr, vvudmv, vvumxy, ncarg_cbind.
245
247 Copyright (C) 1987-2009
248 University Corporation for Atmospheric Research
249 The use of this Software is governed by a License Agreement.
251UNIX April 1993 VELVCT(3NCARG)