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

6       Tdpack_params - This document briefly describes all internal parameters
7       of Tdpack.
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DESCRIPTION

10       Tdpack currently supports some fifteen parameters.  The current values
11       may be retrieved using one of the routines TDGETI, TDGETR, or TDGTRS.
12       Parameter values may be reset using one of the routines TDSETI, TDSETR,
13       or TDSTRS.
14
15       The Tdpack parameter descriptions appear below in alphabetical order.
16       Each description begins with a line giving the parameter name and the
17       intrinsic FORTRAN type of the parameter.
18
19       'CS1' - Real
20              Character Size 1.  This is a multiplier for the sizes of all
21              characters drawn by the routine TDLBLS.
22
23              The default value of 'CS1' is 1.
24
25       'CS2' - Real
26              Character Size 2.  This is a multiplier for the sizes of all
27              characters drawn by the routine TDLBLA.  Exactly how it is set
28              depends on how the current reference parallelogram has been
29              defined.  If the current reference parallelogram has sides of
30              length 1, then it is appropriate to set
31
32                'CS2'='CS1'*MIN(UMAX-UMIN,VMAX-VMIN,WMAX-WMIN)
33
34              where UMIN, UMAX, VMIN, VMAX, WMIN, and WMAX are defined like
35              the arguments of TDLBLS. Note that, if you call TDLBLS, it
36              resets 'CS2' in this fashion, and it does not restore the
37              original value before return.
38
39              The default value of 'CS2' is 1.
40
41       'FOV' - Real
42              When 'SET' has a non-zero value, specifying that TDINIT is to
43              call the SPPS routine SET, then 'FOV' specifies the desired
44              field of view, in degrees, to be seen in the projection plane;
45              its value is used to compute appropriate values for the
46              arguments in the call to SET.
47
48              The default value of 'FOV' is 20.
49
50       'HND' - Integer
51              A zero value specifies that the UVW coordinate system is to be
52              right-handed (the default), while a non-zero value says that it
53              is to be left-handed.  Changing the value of 'HND' mostly
54              affects the behavior of TDINIT - it changes the values of the
55              projection coefficients precomputed and stored in TDPACK common
56              blocks - but it also affects the behavior of the routines TDDTRI
57              and TDLBLS; for this reason, you should not change the value of
58              'HND' between a call to TDINIT and an ensuing call to one of the
59              other two routines, as this would lead to inconsistent behavior.
60              (Most likely, you will decide what the handedness of your
61              coordinate system is, change the value of 'HND' accordingly, and
62              leave that value unchanged thereafter.)
63
64              The default value of 'HND' is 0, specifying a right-handed
65              coordinate system.
66
67       'LSU', 'LSV', and 'LSW' - Real
68              If one or more of these three values is non-zero, then the
69              3-space point ('LSU','LSV','LSW') is the position of the light
70              source assumed by TDDTRI in rendering the triangles in the
71              triangle list.
72
73              The default values are all 0., which, by convention, specifies a
74              light source at the position (UMID,VMID,WMID), where UMID, VMID,
75              and WMID are as specified in the last call to TDINIT.
76
77       'SET' - Integer
78              If this flag is equal to 1 (the default), calling TDINIT will
79              result in a call to the SPPS routine SET to define the mapping
80              from the "user coordinate system" (the X/Y projection plane) to
81              the "fractional coordinate system" (the same as the GKS NDC
82              space); that call will be done in such a way as to give a field
83              of view of 'FOV' degrees and to use the portion of the plotter
84              frame defined by the internal parameters 'VPL', 'VPR', 'VPB',
85              and 'VPT'.  If 'SET' is given the value 0, no such call to SET
86              will be done and the user will be expected to have called it.
87              In the future, other non-zero values of 'SET' may be implemented
88              which will result in TDINIT's doing a call to SET according to
89              some other criterion.
90
91              The default value of 'SET' is 1, specifying that a SET call
92              should be done by TDINIT.
93
94       'SHD' - Integer
95              The value of 'SHD' affects the behavior of TDDTRI when it is
96              picking the fill color to be used for a triangle and the
97              rendering style for the triangle implies that the color index is
98              to be chosen by computing the angle between two vectors - the
99              normal to the triangle and the vector from its center to the
100              light source - and then mapping that angle into a specified
101              range of color indices (thus shading the surface).
102
103              If the value of 'SHD' is zero, angles between 0 and 90 are
104              mapped linearly into the specified range of color indices, from
105              lowest to highest, while angles between 90 and 180 are mapped
106              linearly into that same range, from highest to lowest. The
107              effect of this is essentially to use two light sources, one at
108              the position ('LSU','LSV','LSW') and the other at an exactly
109              opposite position relative to the center of the triangle.
110
111              If the value of 'SHD' is non-zero, angles between 0 and 180 are
112              mapped linearly into the specified range of color indices, from
113              lowest to highest. The effect of this is essentially to use a
114              single light source, at the position ('LSU','LSV','LSW').
115
116              Note that, in both cases, it is the user's responsibility to
117              define the colors associated with the color indices in the
118              specified range to achieve the desired effect. (Normally, the
119              colors associated with the beginning of the range of color
120              indices should be the lightest and the colors associated with
121              the end of that range should be the darkest.) For help in
122              defining colors, see the code of the examples.
123
124              The default value of 'SHD' is zero.
125
126       'STE' - Integer
127              When 'STE' is zero (the default), then stereo pairs are drawn
128              using a single image plane which is perpendicular to the line
129              joining a point midway between the eyes to the point looked at.
130              If 'STE' is set non-zero, then the view from each eye is drawn
131              using an image plane which is perpendicular to the line joining
132              that eye to the point looked at.  (In practice, this probably
133              makes little difference.)
134
135              Changing this parameter changes the values of the projection
136              coefficients precomputed by TDINIT and stored in TDPACK common
137              blocks.
138
139              The default value of 'STE' is 0, specifying that stereo pairs
140              should be drawn using a single image plane perpendicular to the
141              line from the midpoint of the eyes to the point looked at.
142
143       'VPB', 'VPL', 'VPR', and 'VPT' - Real
144              The values of these parameters specify the positions of the
145              bottom, left, right, and top edges, respectively, of a desired
146              viewport within the plotter frame. Each is given a value between
147              0 and 1, inclusive, specifying the position as a fraction of the
148              distance across the plotter frame from left to right or from
149              bottom to top.
150
151              These values are used when the SPPS routine SET is called by
152              TDINIT (which happens when the internal parameter 'SET' has a
153              non-zero value).
154
155              The default values of 'VPB', 'VPL', 'VPR', and 'VPT' are .05,
156              .05, .95, and .95, respectively, specifying the use of most of
157              the plotter frame.
158
159       'Rendering-Style arrays' - Integer
160              The internal parameter arrays that define rendering styles are
161              accessed using the routines TDGTRS (to get the complete
162              definition of a specific rendering style) and TDSTRS (to
163              redefine a specific rendering style). Sixty-four different
164              rendering styles may be defined, indexed 1 through 64; each is
165              defined by an array of ten quantities, seven of which are of
166              type INTEGER (named IFC1, IFC2, IFC3, IFC4, ILC1, ILC2, and
167              ILTD) and three of which are of type REAL (named USTP, VSTP, and
168              WSTP). These quantities may be described as follows:
169
170                     IFC1 and IFC2 are color indices specifying a range of
171                     colors to be used for the "bottom" side of a surface
172                     (where function values are less than the value on the
173                     surface). If IFC1 is negative, filling of triangles seen
174                     from the "bottom" is turned off. If IFC1 is zero or
175                     greater, but IFC2 is less than or equal to it, the color
176                     with index IFC1 is used. If IFC1 is zero or greater and
177                     IFC2 is greater than IFC1, then a range of color indices
178                     is specified; colors near the beginning of that range are
179                     used for triangles that are nearly perpendicular to the
180                     line of sight, while colors near the end of that range
181                     are used for triangles more nearly parallel to the line
182                     of sight. (Normally, one should make triangles
183                     perpendicular to the line of sight lighter than those
184                     parallel to the line of sight.)
185
186                     IFC3 and IFC4 are color indices specifying a range of
187                     colors to be used for the "top" side of a surface (where
188                     function values are greater than the value on the
189                     surface). If IFC3 is negative, filling of triangles seen
190                     from the "top" is turned off. If IFC3 is zero or greater,
191                     but IFC4 is less than or equal to it, the color with
192                     index IFC3 is used. If IFC3 is zero or greater and IFC4
193                     is greater than IFC3, then a range of color indices is
194                     specified; colors near the beginning of that range are
195                     used for triangles that are nearly perpendicular to the
196                     line of sight, while colors near the end of that range
197                     are used for triangles more nearly parallel to the line
198                     of sight. (Normally, one should make triangles
199                     perpendicular to the line of sight lighter than those
200                     parallel to the line of sight.)
201
202                     ILC1 is the color index specifying a color to be used for
203                     lines drawn on the "bottom" side of a surface. If ILC1 is
204                     negative, the drawing of these lines is turned off.
205
206                     ILC2 is the color index specifying a color to be used for
207                     lines drawn on the "top" side of a surface. If ILC2 is
208                     negative, the drawing of these lines is turned off.
209
210                     ILTD is a flag, which, if set non-zero, turns on the
211                     drawing of the edges of the individual triangles into
212                     which surfaces have been decomposed.
213
214                     USTP, VSTP, and WSTP are the distances between slices in
215                     the U, V, and W directions, respectively. If a given
216                     value is zero, the associated slice lines are not drawn.
217
218                     Note: It is the responsibility of the user to call the
219                     GKS routine GSCR to define all of the colors to be used.
220

SEE ALSO

222       Online: tdclrs, tdctri, tddtri, tdgeti, tdgetr, tdgrds, tdgrid, tdgtrs,
223       tdinit, tditri, tdlbla, tdlbls, tdline, tdlnpa, tdmtri, tdotri, tdpack,
224       tdpara, tdplch, tdprpa, tdprpi, tdprpt, tdseti, tdsetr, tdsort, tdstri,
225       tdstrs
226
228       Copyright (C) 1987-2009
229       University Corporation for Atmospheric Research
230       The use of this Software is governed by a License Agreement.
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234UNIX                               July 1997             Tdpack_params(3NCARG)
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