Ubuntu Manpage: Tdpack_params - This document briefly describes all internal parameters of Tdpack.

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NAME

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

DESCRIPTION

Tdpack currently supports some fifteen parameters. The current values may be retrieved using one of the
routines TDGETI, TDGETR, or TDGTRS. Parameter values may be reset using one of the routines TDSETI,
TDSETR, or TDSTRS.

The Tdpack parameter descriptions appear below in alphabetical order. Each description begins with a line
giving the parameter name and the intrinsic FORTRAN type of the parameter.

'CS1' - Real
Character Size 1. This is a multiplier for the sizes of all characters drawn by the routine
TDLBLS.

The default value of 'CS1' is 1.

'CS2' - Real
Character Size 2. This is a multiplier for the sizes of all characters drawn by the routine
TDLBLA. Exactly how it is set depends on how the current reference parallelogram has been
defined. If the current reference parallelogram has sides of length 1, then it is appropriate to
set

'CS2'='CS1'*MIN(UMAX-UMIN,VMAX-VMIN,WMAX-WMIN)

where UMIN, UMAX, VMIN, VMAX, WMIN, and WMAX are defined like the arguments of TDLBLS. Note that,
if you call TDLBLS, it resets 'CS2' in this fashion, and it does not restore the original value
before return.

The default value of 'CS2' is 1.

'FOV' - Real
When 'SET' has a non-zero value, specifying that TDINIT is to call the SPPS routine SET, then
'FOV' specifies the desired field of view, in degrees, to be seen in the projection plane; its
value is used to compute appropriate values for the arguments in the call to SET.

The default value of 'FOV' is 20.

'HND' - Integer
A zero value specifies that the UVW coordinate system is to be right-handed (the default), while a
non-zero value says that it is to be left-handed. Changing the value of 'HND' mostly affects the
behavior of TDINIT - it changes the values of the projection coefficients precomputed and stored
in TDPACK common blocks - but it also affects the behavior of the routines TDDTRI and TDLBLS; for
this reason, you should not change the value of 'HND' between a call to TDINIT and an ensuing call
to one of the other two routines, as this would lead to inconsistent behavior. (Most likely, you
will decide what the handedness of your coordinate system is, change the value of 'HND'
accordingly, and leave that value unchanged thereafter.)

The default value of 'HND' is 0, specifying a right-handed coordinate system.

'LSU', 'LSV', and 'LSW' - Real
If one or more of these three values is non-zero, then the 3-space point ('LSU','LSV','LSW') is
the position of the light source assumed by TDDTRI in rendering the triangles in the triangle
list.

The default values are all 0., which, by convention, specifies a light source at the position
(UMID,VMID,WMID), where UMID, VMID, and WMID are as specified in the last call to TDINIT.

'SET' - Integer
If this flag is equal to 1 (the default), calling TDINIT will result in a call to the SPPS routine
SET to define the mapping from the "user coordinate system" (the X/Y projection plane) to the
"fractional coordinate system" (the same as the GKS NDC space); that call will be done in such a
way as to give a field of view of 'FOV' degrees and to use the portion of the plotter frame
defined by the internal parameters 'VPL', 'VPR', 'VPB', and 'VPT'. If 'SET' is given the value 0,
no such call to SET will be done and the user will be expected to have called it. In the future,
other non-zero values of 'SET' may be implemented which will result in TDINIT's doing a call to
SET according to some other criterion.

The default value of 'SET' is 1, specifying that a SET call should be done by TDINIT.

'SHD' - Integer
The value of 'SHD' affects the behavior of TDDTRI when it is picking the fill color to be used for
a triangle and the rendering style for the triangle implies that the color index is to be chosen
by computing the angle between two vectors - the normal to the triangle and the vector from its
center to the light source - and then mapping that angle into a specified range of color indices
(thus shading the surface).

If the value of 'SHD' is zero, angles between 0 and 90 are mapped linearly into the specified
range of color indices, from lowest to highest, while angles between 90 and 180 are mapped
linearly into that same range, from highest to lowest. The effect of this is essentially to use
two light sources, one at the position ('LSU','LSV','LSW') and the other at an exactly opposite
position relative to the center of the triangle.

If the value of 'SHD' is non-zero, angles between 0 and 180 are mapped linearly into the specified
range of color indices, from lowest to highest. The effect of this is essentially to use a single
light source, at the position ('LSU','LSV','LSW').

Note that, in both cases, it is the user's responsibility to define the colors associated with the
color indices in the specified range to achieve the desired effect. (Normally, the colors
associated with the beginning of the range of color indices should be the lightest and the colors
associated with the end of that range should be the darkest.) For help in defining colors, see the
code of the examples.

The default value of 'SHD' is zero.

'STE' - Integer
When 'STE' is zero (the default), then stereo pairs are drawn using a single image plane which is
perpendicular to the line joining a point midway between the eyes to the point looked at. If 'STE'
is set non-zero, then the view from each eye is drawn using an image plane which is perpendicular
to the line joining that eye to the point looked at. (In practice, this probably makes little
difference.)

Changing this parameter changes the values of the projection coefficients precomputed by TDINIT
and stored in TDPACK common blocks.

The default value of 'STE' is 0, specifying that stereo pairs should be drawn using a single image
plane perpendicular to the line from the midpoint of the eyes to the point looked at.

'VPB', 'VPL', 'VPR', and 'VPT' - Real
The values of these parameters specify the positions of the bottom, left, right, and top edges,
respectively, of a desired viewport within the plotter frame. Each is given a value between 0 and
1, inclusive, specifying the position as a fraction of the distance across the plotter frame from
left to right or from bottom to top.

These values are used when the SPPS routine SET is called by TDINIT (which happens when the
internal parameter 'SET' has a non-zero value).

The default values of 'VPB', 'VPL', 'VPR', and 'VPT' are .05, .05, .95, and .95, respectively,
specifying the use of most of the plotter frame.

'Rendering-Style arrays' - Integer
The internal parameter arrays that define rendering styles are accessed using the routines TDGTRS
(to get the complete definition of a specific rendering style) and TDSTRS (to redefine a specific
rendering style). Sixty-four different rendering styles may be defined, indexed 1 through 64; each
is defined by an array of ten quantities, seven of which are of type INTEGER (named IFC1, IFC2,
IFC3, IFC4, ILC1, ILC2, and ILTD) and three of which are of type REAL (named USTP, VSTP, and
WSTP). These quantities may be described as follows:

IFC1 and IFC2 are color indices specifying a range of colors to be used for the "bottom"
side of a surface (where function values are less than the value on the surface). If IFC1
is negative, filling of triangles seen from the "bottom" is turned off. If IFC1 is zero or
greater, but IFC2 is less than or equal to it, the color with index IFC1 is used. If IFC1
is zero or greater and IFC2 is greater than IFC1, then a range of color indices is
specified; colors near the beginning of that range are used for triangles that are nearly
perpendicular to the line of sight, while colors near the end of that range are used for
triangles more nearly parallel to the line of sight. (Normally, one should make triangles
perpendicular to the line of sight lighter than those parallel to the line of sight.)

IFC3 and IFC4 are color indices specifying a range of colors to be used for the "top" side
of a surface (where function values are greater than the value on the surface). If IFC3 is
negative, filling of triangles seen from the "top" is turned off. If IFC3 is zero or
greater, but IFC4 is less than or equal to it, the color with index IFC3 is used. If IFC3
is zero or greater and IFC4 is greater than IFC3, then a range of color indices is
specified; colors near the beginning of that range are used for triangles that are nearly
perpendicular to the line of sight, while colors near the end of that range are used for
triangles more nearly parallel to the line of sight. (Normally, one should make triangles
perpendicular to the line of sight lighter than those parallel to the line of sight.)

ILC1 is the color index specifying a color to be used for lines drawn on the "bottom" side
of a surface. If ILC1 is negative, the drawing of these lines is turned off.

ILC2 is the color index specifying a color to be used for lines drawn on the "top" side of
a surface. If ILC2 is negative, the drawing of these lines is turned off.

ILTD is a flag, which, if set non-zero, turns on the drawing of the edges of the individual
triangles into which surfaces have been decomposed.

USTP, VSTP, and WSTP are the distances between slices in the U, V, and W directions,
respectively. If a given value is zero, the associated slice lines are not drawn.

Note: It is the responsibility of the user to call the GKS routine GSCR to define all of
the colors to be used.

COPYRIGHT

       Copyright (C) 1987-2009
       University Corporation for Atmospheric Research
       The use of this Software is governed by a License Agreement.

UNIX                                                July 1997                              Tdpack_params(3NCARG)

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