Provided by: libmath-planepath-perl_125-1_all 
NAME
Math::PlanePath::GreekKeySpiral -- square spiral with Greek key motif
SYNOPSIS
use Math::PlanePath::GreekKeySpiral;
my $path = Math::PlanePath::GreekKeySpiral->new;
my ($x, $y) = $path->n_to_xy (123);
DESCRIPTION
This path makes a spiral with a Greek key scroll motif,
39--38--37--36 29--28--27 24--23 5
| | | | | |
40 43--44 35 30--31 26--25 22 4
| | | | | |
41--42 45 34--33--32 19--20--21 ... 3
| | |
48--47--46 5---6---7 18 15--14 99 96--95 2
| | | | | | | | |
49 52--53 4---3 8 17--16 13 98--97 94 1
| | | | | | |
50--51 54 1---2 9--10--11--12 91--92--93 <- Y=0
| |
57--56--55 68--69--70 77--78--79 90 87--86 -1
| | | | | | | |
58 61--62 67--66 71 76--75 80 89--88 85 -2
| | | | | | | |
59--60 63--64--65 72--73--74 81--82--83--84 -3
^
-3 -2 -1 X=0 1 2 3 4 5 6 7 8 ...
The repeating figure is a 3x3 pattern
|
* *---*
| | | right vertical
*---* * going upwards
|
*---*---*
|
The turn excursion is to the outside of the 3-wide channel and forward in the direction of
the spiral. The overall spiraling is the same as the "SquareSpiral", but composed of 3x3
sub-parts.
Sub-Part Joining
The verticals have the "entry" to each figure on the inside edge, as for example N=90 to
N=91 above. The horizontals instead have it on the outside edge, such as N=63 to N=64
along the bottom. The innermost N=1 to N=9 is a bottom horizontal going right.
*---*---*
| | bottom horizontal
*---* * going rightwards
| |
--*---* *-->
On the horizontals the excursion part is still "forward on the outside", as for example
N=73 through N=76, but the shape is offset. The way the entry is alternately on the
inside and outside for the vertical and horizontal is necessary to make the corners join.
Turn
An optional "turns => $integer" parameter controls the turns within the repeating figure.
The default is "turns=>2". Or for example "turns=>4" begins
turns => 4
105-104-103-102-101-100 79--78--77--76--75 62--61--60--59
| | | | | |
106 119-120-121-122 99 80 87--88--89 74 63 66--67 58
| | | | | | | | | | | |
107 118 115-114 123 98 81 86--85 90 73 64--65 68 57
| | | | | | | | | | | |
108 117-116 113 124 97 82--83--84 91 72--71--70--69 56
| | | | | |
109-110-111-112 125 96--95--94--93--92 51--52--53--54--55
| |
130-129-128-127-126 17--18--19--20--21 50 37--36--35--34
| | | | | |
131 144-145-146-147 16 9-- 8-- 7 22 49 38 41--42 33
| | | | | | | | | | | |
132 143 140-139 148 15 10--11 6 23 48 39--40 43 32
| | | | | | | | | | | |
133 142-141 138 149 14--13--12 5 24 47--46--45--44 31
| | | | | |
134-135-136-137 150 1-- 2-- 3-- 4 25--26--27--28--29--30
|
..-152-151
The count of turns is chosen to make "turns=>0" a straight line, the same as the
"SquareSpiral". "turns=>1" is a single wiggle,
turns => 1
66--65--64 61--60 57--56 53--52--51
| | | | | | | |
67--68 63--62 59--58 55--54 49--50
| |
70--69 18--17--16 13--12--11 48--47
| | | | | |
71--72 19--20 15--14 9--10 45--46
| | | |
... 22--21 2-- 3 8-- 7 44--43
| | | | |
23--24 1 4-- 5-- 6 41--42
| |
26--25 30--31 34--35 40--39
| | | | | |
27--28--29 32--33 36--37--38
In general the repeating figure is a square of turns+1 points on each side, spiralling in
and then out again.
FUNCTIONS
See "FUNCTIONS" in Math::PlanePath for behaviour common to all path classes.
"$path = Math::PlanePath::GreekKeySpiral->new ()"
"$path = Math::PlanePath::GreekKeySpiral->new (turns => $integer)"
Create and return a new Greek key spiral object. The default "turns" is 2.
"($x,$y) = $path->n_to_xy ($n)"
Return the X,Y coordinates of point number $n on the path.
For "$n < 1" the return is an empty list, it being considered the path starts at 1.
"$n = $path->xy_to_n ($x,$y)"
Return the point number for coordinates "$x,$y". $x and $y are each rounded to the
nearest integer, which has the effect of treating each N in the path as centred in a
square of side 1, so the entire plane is covered.
SEE ALSO
Math::PlanePath, Math::PlanePath::SquareSpiral
Jo Edkins Greek Key pages "http://gwydir.demon.co.uk/jo/greekkey/index.htm"
HOME PAGE
<http://user42.tuxfamily.org/math-planepath/index.html>
LICENSE
Copyright 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017 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/>.