NAME
PDL::Graphics::TriD::Rout  Helper routines for Threedimensional graphics
DESCRIPTION
This module is for miscellaneous PPdefined utility routines for the PDL::Graphics::TriD module. Currently, there are
FUNCTIONS
combcoords
Signature: (x(); y(); z();
float [o]coords(tri=3);)
Combine three coordinates into a single piddle.
Combine x, y and z to a single piddle the first dimension of which is 3. This routine does dataflow automatically.
combcoords does not process bad values. It will set the badvalue flag of all output piddles if the flag is set for any of the input piddles.
repulse
Signature: (coords(nc,np);
[o]vecs(nc,np);
int [t]links(np);;
double boxsize;
int dmult;
double a;
double b;
double c;
double d;
)
Repulsive potential for moleculelike constructs.
repulse
uses a hash table of cubes to quickly calculate a repulsive force that vanishes at infinity for many objects. For use by the module PDL::Graphics::TriD::MathGraph. For definition of the potential, see the actual function.
repulse does not process bad values. It will set the badvalue flag of all output piddles if the flag is set for any of the input piddles.
attract
Signature: (coords(nc,np);
int from(nl);
int to(nl);
strength(nl);
[o]vecs(nc,np);;
double m;
double ms;
)
Attractive potential for moleculelike constructs.
attract
is used to calculate an attractive force for many objects, of which some attract each other (in a way like molecular bonds). For use by the module PDL::Graphics::TriD::MathGraph. For definition of the potential, see the actual function.
attract does not process bad values. It will set the badvalue flag of all output piddles if the flag is set for any of the input piddles.
vrmlcoordsvert
Signature: (vertices(n=3); char* space; char* fd)
info not available
vrmlcoordsvert does not process bad values. It will set the badvalue flag of all output piddles if the flag is set for any of the input piddles.
contour_segments
This is the interface for the pp routine contour_segments_internal  it takes 3 piddles as input
$c
is a contour value (or a list of contour values)
$data
is an [m,n] array of values at each point
$points
is a list of [3,m,n] points, it should be a grid monotonically increasing with m and n.
contour_segments returns a reference to a Perl array of line segments associated with each value of $c
. It does not (yet) handle missing data values.
 Algorithm

The data array represents samples of some field observed on the surface described by points. For each contour value we look for intersections on the line segments joining points of the data. When an intersection is found we look to the adjoining line segments for the other end(s) of the line segment(s). So suppose we find an intersection on an xsegment. We first look down to the left ysegment, then to the right ysegment and finally across to the next xsegment. Once we find one in a box (two on a point) we can quit because there can only be one. After we are done with a given xsegment, we look to the leftover possibilities for the adjoining ysegment. Thus the contours are built as a collection of line segments rather than a set of closed polygons.
AUTHOR
Copyright (C) 2000 James P. Edwards Copyright (C) 1997 Tuomas J. Lukka. All rights reserved. There is no warranty. You are allowed to redistribute this software / documentation under certain conditions. For details, see the file COPYING in the PDL distribution. If this file is separated from the PDL distribution, the copyright notice should be included in the file.