Category : EmTeX is a TeX/LaTeX document editor
Archive   : LATEX.ZIP
Filename : BEZIER.DOC

% BEZIER DOCUMENT-STYLE OPTION - released 17 December 1985
% for LaTeX version 2.09
% Copyright (C) 1985 by Leslie Lamport

% In a picture environment, writing
%
% \bezier{N}(AX,AY)(BX,BY)(CX,CY)
%
% plots a quadratic Bezier curve from (AX,AY) to (CX,CY), with (BX,BY)
% as the third Bezier point, using N+1 equally spaced points.
%
% \bezier{N}(AX,AY)(BX,BY)(CX,CY) ==
% BEGIN
% @sc := N
% @scp := @sc+1
% \@xb := 2 * (BX - AX) * \unitlength
% \@xa := ((CX-AX)*\unitlength - \@xb)/@sc
% \@yb := 2 * (BY - AY) * \unitlength
% \@ya := ((CY-AY)*\unitlength - \@yb)/@sc
% \@pt := square rule of width \@wholewidth
% @t := 0
% WHILE @t < @scp
% DO \@x := ((@t*\@xa + @xb) / @sc) * t
% \@y := ((@t*\@ya + @yb) / @sc) * t
% plot pt with relative coords (\@x,\@y)
% @t := @t+1
% OD

\newcounter{@sc}
\newcounter{@scp}
\newcounter{@t}
\newlength{\@x}
\newlength{\@xa}
\newlength{\@xb}
\newlength{\@y}
\newlength{\@ya}
\newlength{\@yb}
\newsavebox{\@pt}

\def\bezier#1(#2,#3)(#4,#5)(#6,#7){\c@@sc#1\relax
\c@@scp\c@@sc \advance\c@@scp\@ne
\@xb #4\unitlength \advance\@xb -#2\unitlength \multiply\@xb \tw@
\@xa #6\unitlength \advance\@xa -#2\unitlength
\advance\@xa -\@xb \divide\@xa\c@@sc
\@yb #5\unitlength \advance\@yb -#3\unitlength \multiply\@yb \tw@
\@ya #7\unitlength \advance\@ya -#3\unitlength
\advance\@ya -\@yb \divide\@ya\c@@sc
\setbox\@pt\hbox{\vrule height\@halfwidth depth\@halfwidth
width\@wholewidth}\c@@t\z@
\put(#2,#3){\@whilenum{\c@@t<\c@@scp}\do
{\@x\c@@t\@xa \advance\@x\@xb \divide\@x\c@@sc \multiply\@x\c@@t
\@y\c@@t\@ya \advance\@y\@yb \divide\@y\c@@sc \multiply\@y\c@@t
\raise \@y \hbox to \z@{\hskip \@x\unhcopy\@pt\hss}%
\advance\c@@t\@ne}}}


% of commands of the type specified below, does the following,
% where t, dt, dx, and dy are counters,
%
% t := 0
% dt := DT
% dx := 0
% dy := 0
% WHILE t < MAX
% DO plot the point (X + (dx/SCALE)), Y + (dy/SCALE))
% t := t + dt
% execute COMMANDS
% OD
%
% COMMANDS may include only the commands \set, \add, \mul, or \div,
% defined as follows, where
% CTR == counter name,
% VAL == either an integer (like 2145 or -7), or
% \value{CTR'}, where CTR' a counter name, or
% -\value{CTR'}
%
% \set{CTR}{VAL}
% This command performs the operation CTR := VAL
%
% \add{CTR}{VAL}
% Performs the operation CTR := CTR + VAL
%
% \mul{CTR}{VAL}
% Performs the operation CTR := CTR * VAL
%
% \div{CTR}{VAL}
% Performs the operation CTR := CTR / VAL
% (this is integer division, with 5/3 = 1 and
% -5/3 = 5/(-3) = -1)
%
% There should be no spaces in COMMANDS. However, the command \ can
% be used for readabiilty--e.g.,
% \set{foo}{dt}\ \mul{foo}{3}
%
%
% HINTS:
% \plot'ing takes a long time, so start with DT large, and make it
% small only for the final draft.
%

%\newcounter{t}
%\newcounter{dt}
%\newcounter{dx}
%\newcounter{dy}
%
%\def\set#1#2{\csname c@#1\endcsname#2}
%\def\@div#1#2{\divide\csname c@#1\endcsname#2}
%\def\mul#1#2{\multiply\csname c@#1\endcsname#2}
%\def\add#1#2{\advance\csname c@#1\endcsname#2}
%



%\def\plot#1#2#3#4{\let\div\@div \def\ {}\c@t\z@ \c@t\z@
% \c@dt#1\c@dx\z@ \c@dy\z@\edef\@tempa{#4}\@tempdima\unitlength
% \divide\@tempdima #3\relax
% \setbox\@pt\hbox{\vrule height\@halfwidth depth\@halfwidth
% width\@wholewidth}\@whilenum{\c@t<#2}\do
% {\raise \c@dy\@tempdima \hbox to \z@{\hskip \c@dx\@tempdima
% \unhcopy\@pt\hss
% }\advance\c@t\c@dt\@tempa}}
%

\endinput