/ 
Math-PlanePath-129
River stage one • 3 direct dependents • 4 total dependents
/ Math::PlanePath::FilledRings

NAME

Math::PlanePath::FilledRings -- concentric filled lattice rings

SYNOPSIS

use Math::PlanePath::FilledRings;
my $path = Math::PlanePath::FilledRings->new;
my ($x, $y) = $path->n_to_xy (123);

DESCRIPTION

This path puts points on integer X,Y pixels of filled rings with radius 1 unit each ring.

                110-109-108-107-106                        6
               /                   \
        112-111  79--78--77--76--75 105-104                5
          |    /                   \      |
    114-113  80  48--47--46--45--44  74 103-102            4
      |    /      |               |    \      |
    115  81  50--49  27--26--25  43--42  73 101            3
   /   /      |    /           \      |    \   \
116  82  52--51  28  14--13--12  24  41--40  72 100        2
  |   |   |    /   /           \   \      |   |   |
117  83  53  29  15   5-- 4-- 3  11  23  39  71  99        1
  |   |   |   |   |   |       |   |   |   |   |   |
118  84  54  30  16   6   1-- 2  10  22  38  70  98   <- Y=0
  |   |   |   |   |   |        /   /   /   /   /   /
119  85  55  31  17   7-- 8-- 9  21  37  69  97 137       -1
  |   |   |    \   \           /   /      |   |   |
120  86  56--57  32  18--19--20  36  67--68  96 136       -2
   \   \      |    \           /      |    /   /
    121  87  58--59  33--34--35  65--66  95 135           -3
      |    \      |               |    /      |
    122-123  88  60--61--62--63--64  94 133-134           -4
          |    \                   /      |
        124-125  89--90--91--92--93 131-132               -5
               \                   /
                126-127-128-129-130

                          ^
 -6  -5  -4  -3  -2  -1  X=0  1   2   3   4   5   6

For example the ring N=22 to N=37 is all the points

2.5 < hypot(X,Y) < 3.5
where hypot(X,Y) = sqrt(X^2+Y^2)

N Start

The default is to number points starting N=1 as shown above. An optional n_start can give a different start with the same shape. For example to start at 0,

      26-25-24          n_start => 0
     /        \
   27 13-12-11 23
  /  /        \  \
28 14  4--3--2 10 22
 |  |  |     |  |  |
29 15  5  0--1  9 21
 |  |  |      /  /  /
30 16  6--7--8 20 36
  \  \        /  /
   31 17-18-19 35
     \        /
    8 32-33-34

The only effect is to push the N values by a constant amount but can help match N on the axes to counts of X,Y points < R or similar.

FUNCTIONS

See "FUNCTIONS" in Math::PlanePath for the behaviour common to all path classes.

$path = Math::PlanePath::FilledRings->new ()
$path = Math::PlanePath::FilledRings->new (n_start => $n)

Create and return a new path object.

OEIS

Entries in Sloane's Online Encyclopedia of Integer Sequences related to this path include,

A036705  first diffs of N on X axis,
           being count of X,Y points n-1/2 < norm <= n+1/2
A036706  1/4 of those diffs

n_start=1 (the default)
  A036707  N/2+X-1 along X axis,
             being count norm <= n+1/2 in half plane
  A036708  (N(X,0)-N(X-1,0))/2+1,
             first diffs of the half plane count

n_start=0
  A036704  N on X axis, from X=1 onwards
             count of X,Y points norm <= n+1/2

SEE ALSO

Math::PlanePath, Math::PlanePath::PixelRings, Math::PlanePath::Hypot, Math::PlanePath::MultipleRings

HOME PAGE

http://user42.tuxfamily.org/math-planepath/index.html

LICENSE

Copyright 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020 Kevin Ryde

This file is part of Math-PlanePath.

Math-PlanePath is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version.

Math-PlanePath is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with Math-PlanePath. If not, see <http://www.gnu.org/licenses/>.