1INIT3D(3NCARG)                   NCAR GRAPHICS                  INIT3D(3NCARG)
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NAME

6       INIT3D - Draws an isosurface when used in conjunction with entry DANDR.
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SYNOPSIS

9       CALL INIT3D (EYE,NU,NV,NW,ST1,LX,NY,IS2,IU,S)
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STATUS

12       This routine is part of the obsolete Isosrfhr utility.  Isosrfhr has
13       been replaced by the Isosurface utility.  To see the Isosurface utility
14       overview man page, type "man isosurface".
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DESCRIPTION

17       EYE         (an input array of type REAL, dimensioned 3) is the
18                   position of the eye in the UVW coordinate system.  Objects
19                   are considered to be in a box with 2 extreme corners at
20                   (1,1,1) and (NU,NV,NW).  The eye position must have
21                   positive coordinates away from the coordinate planes U = 0,
22                   V = 0, and W = 0.  While gaining experience with the
23                   package, use EYE(1) = 5.*NU, EYE(2) = 4.*NV, and EYE(3) =
24                   3.*NW.
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26       NU          (an input expression of type INTEGER) defines the range to
27                   be used for the U dimension of the 3-D UVW grid.
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29       NV          (an input expression of type INTEGER) defines the range to
30                   be used for the V dimension of the 3-D UVW grid.
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32       NW          (an input expression of type INTEGER) defines the range to
33                   be used for the W dimension of the 3-D UVW grid.
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35       ST1         (an input array of type REAL) used as scratch work space.
36                   It must be dimensioned at least of size NV*NW*2 words.
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38       LX          (an input array of type INTEGER) which is the first
39                   dimension of array IS2.  It must be of a length to hold NX
40                   bits.  On a 64 bit machine it would be LX=(NX-1)/64+1.
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42       NY          (an input expression of type INTEGER) defines the range of
43                   cells in the Y-direction of the XY pixel model of the image
44                   plane.  NY is also the second dimension of array IS2.
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46       IS2         (an input array of type INTEGER) which holds the XY pixel
47                   model of the image plane.  It is dimensioned LX by NY.  The
48                   pixel model contains NX by NY elements.  The sizes of NX
49                   and NY vary with the choice of options.  For example, if
50                   hidden lines are drawn, NX and NY (and LX) can be smaller
51                   than when hidden lines are not drawn.  If some visible
52                   lines are not drawn, NX and NY (and LX) must be made
53                   larger.  As a guide, some examples which have been adequate
54                   are:
55                        GIVEN                 USE
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57                       NU  NV  NW            NX  NY
58                   --------------------------------
59                      100 100  60           200 200
60                       60  60  60           110 110
61                       40  40  40            75  75
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64       IU          (an input expression of type INTEGER) defines the unit
65                   number of a scratch file for the package.  ST1 will be
66                   written NU times on this file.
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68       S           (an input array of type REAL, dimensioned 4) contains the
69                   world coordinates of the area where the picture is to be
70                   drawn.  That is, all plotting coordinates generated will be
71                   bounded as follows:  X coordinates will be between S(1) and
72                   S(2), Y coordinates will be between S(3) and S(4).  To
73                   prevent distortion, have S(2)-S(1) = S(4)-S(3).
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75                   All coordinates should be in a range between 10.  and 1010.
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USAGE

78       Entries INIT3D and DANDR must be used in tandem to create a plot.
79       First call entry INIT3D to create a set of 2-D perspective planes which
80       are output to a scratch file.  Then, in the calling program you must
81       loop over the U dimension of UVW space starting at the last slab, NU,
82       and moving forward to slab 1.  Initially set all elements of IOBJS to
83       zeros.  Then, at all locations (J,K) where the surface of an object
84       would appear, set IOBJS(J,K) = 1.  When IOBJS(J,K) has been defined for
85       that VW slab (U = NU - I + 1), call the entry DANDR, which draws any
86       object contours based on the 2-D perspective defined for that slab.
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88       An Isosrfhr example of the logical structure of a program follows:
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90        C  Entry INIT3D writes NU 2-D perspective planes, ST1(NV,NW,2),
91        C   of the UVW grid, viewed from the position EYE, to a scratch file.
92        C
93             CALL INIT3D(EYE,NU,NV,NW,ST1,LX,NY,IS2,IU,S)
94        C
95        C NU is the extent of the U dimension.
96        C
97             DO 1 IBKWDS = 1,NU
98             I = NU+1-IBKWDS
99        C
100        C You must define the presence of the objects at each VW grid point for
101        C all slabs in the U direction. Ones are used to indicate the presence
102        C of an object.  Zeros indicate no object.
103        C
104        C      IF (OBJ.EQ.YES) IOBJS(J,K) = 1
105        C      IF (OBJ.EQ.NO)  IOBJS(J,K) = 0
106        C
107        C  DANDR reads ST1(NV,NW,2) for slab I.
108        C
109           1 CALL DANDR(NV,NW,ST1,LX,NX,NY,IS2,IU,S,IOBJS,MV)
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EXAMPLES

113       Use the ncargex command to see the following relevant examples:  tisohr
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ACCESS

116       To use INIT3D load the NCAR Graphics libraries ncarg, ncarg_gks, and
117       ncarg_c, preferably in that order.
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SEE ALSO

120       Online: isosrfhr, dandr, isosurface, isosurface_params, ezisos, isgeti,
121       isgetr, isseti, issetr, pwrzi, ncarg_cbind
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124       Copyright (C) 1987-2009
125       University Corporation for Atmospheric Research
126       The use of this Software is governed by a License Agreement.
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130UNIX                              March 1993                    INIT3D(3NCARG)
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