%%
%% A DANTE-Edition example
%%
%% Example 14-05-1 on page 164.
%%
%% Copyright (C) 2011 Herbert Voss
%%
%% It may be distributed and/or modified under the conditions
%% of the LaTeX Project Public License, either version 1.3
%% of this license or (at your option) any later version.
%%
%% See
http://www.latex-project.org/lppl.txt for details.
%%
%%
%% ====
% Show page(s) 1
%%
\documentclass[]{article}
\pagestyle{empty}
\setlength\textwidth{415.41023pt}
\setlength\parindent{0pt}
\usepackage{pst-node,multido,pst-xkey}
\SpecialCoor
\makeatletter
\define@boolkey[psset]{}[Pst@]{showFP}[true]{}% mark focal point?
\psset{showFP=true} % default
\def\focalPoint{\pst@object{focalPoint}}
\def\focalPoint@i(#1)(#2)(#3)#4{{ % keep everything local
\use@par% % set parameters
\pst@getcoor{#1}\pst@tempA% point A % get coordinates as x y
\pst@getcoor{#2}\pst@tempB% point B %
\pst@getcoor{#3}\pst@tempC% point C %
\pnode(! % set nodes
\pst@tempA /YA exch \pst@number\psyunit div def
/XA exch \pst@number\psxunit div def % x y in user coordinates
\pst@tempB /YB exch \pst@number\psyunit div def
/XB exch \pst@number\psxunit div def
\pst@tempC /YC exch \pst@number\psyunit div def
/XC exch \pst@number\psxunit div def
XA XB XC add add 3.0 div % xSP
YA YB YC add add 3.0 div % ySP
){#4}% % #5 = node name
\ifPst@showFP\qdisk(#4){2pt}\fi}%
\ignorespaces} % mark?
\makeatother
\begin{document}
\psset{unit=0.7}
\begin{pspicture}(-5,-5)(5,5)
\multido{\rA=-5+0.5,\rB=0+0.5,\rC=5+-0.5}{10}{%
\pnode(-5,\rA){A}\pnode(\rB,5){B}\pnode(\rC,-5){C}%
\pspolygon[linecolor=blue](A)(B)(C)%
\focalPoint(A)(B)(C){SP}%
}
\multido{\rA=0+0.5,\rB=5+-0.5,\rC=0+-0.5}{10}{%
\pnode(-5,\rA){A}\pnode(5,\rB){B}\pnode(\rC,-5){C}%
\pspolygon[linecolor=red](A)(B)(C)%
\focalPoint(A)(B)(C){SP}%
}
\multido{\rA=-5+0.5,\rB=0+-0.5,\rC=-5+0.5}{10}{%
\pnode(\rA,5){A}\pnode(5,\rB){B}\pnode(-5,\rC){C}%
\pspolygon[linecolor=cyan](A)(B)(C)%
\focalPoint(A)(B)(C){SP}%
}
\multido{\rA=0+0.5,\rB=5+-0.5,\rC=0+0.5}{10}{%
\pnode(\rA,5){A}\pnode(\rB,-5){B}\pnode(-5,\rC){C}%
\pspolygon[linecolor=magenta](A)(B)(C)%
\focalPoint(A)(B)(C){SP}%
}
\multido{\rA=5+-0.5,\rB=0+-0.5,\rC=-5+0.5}{10}{%
\pnode(5,\rA){A}\pnode(\rB,-5){B}\pnode(\rC,5){C}%
\pspolygon[linecolor=blue](A)(B)(C)%
\focalPoint(A)(B)(C){SP}%
}
\multido{\rA=0+-0.5,\rB=-5+0.5,\rC=0+0.5}{10}{%
\pnode(5,\rA){A}\pnode(-5,\rB){B}\pnode(\rC,5){C}%
\pspolygon[linecolor=red](A)(B)(C)%
\focalPoint(A)(B)(C){SP}%
}
\multido{\rA=5+-0.5,\rB=0+0.5,\rC=5+-0.5}{10}{%
\pnode(\rA,-5){A}\pnode(-5,\rB){B}\pnode(5,\rC){C}%
\pspolygon[linecolor=cyan](A)(B)(C)%
\focalPoint(A)(B)(C){SP}%
}
\multido{\rA=0+-0.5,\rB=-5+0.5,\rC=0+-0.5}{10}{%
\pnode(\rA,-5){A}\pnode(\rB,5){B}\pnode(5,\rC){C}%
\pspolygon[linecolor=magenta](A)(B)(C)%
\focalPoint(A)(B)(C){SP}%
}
\end{pspicture}
\end{document}
