% name of textfile: P9 curvetraceing (DL/Synergetics Feb 91 v1.0)
% ....

% =========

% This file requires the previous download of gonzo.psl
% available from https://www.tinaja.com/pssamp1.shtml

% Make sure the following line agrees with your own gonzo.psl location

(C:/Users/don/Desktop/gonzo/gonzo.psl) run  % use internal gonzo

% ==========


% Shows you several fundamental excercises in curvetracing that you
% can use to draw smooth continuous lines and curves

gutility begin             % turn on the gonzo utilities
nuisance begin             % turn on the nuisance commands
printerror                 % turn on the printing error trapper  

gonzo begin                % turn on the gonzo justification 

/showfullgrid false def    % show entire page grid?

20 20 10 setgrid           % get on a grid

showfullgrid {57 76 showgrid} if               % and maybe show it
 
/cstretch 0.04 def                             % slight character stretch
/sstretch 0.02 def                             % slight space stretch                           
/font2 /Helvetica-Narrow-Bold 0.8 gonzofont    % pick a font

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% curvetrace rules: The curvetrace operator expects an array of form
%  [ x0 y0 ang0  x1 y1 ang1 .... xn yn angn ] curvetrace, where
%
%           x0 is the horizontal position of your first point
%           y0 is the vertical position of your first point
%         ang0 is the direction you wish to LEAVE your first point
%              with  0 = east  90 = north  180 = west  -90 = south
%
%           xn is the horizontal position of your last point
%           yn is the vertical position of your last point
%         angn is the direction you wish to ENTER your last point
%              with  0 = east  90 = north  180 = west  -90 = south
%
%  if you want to see where you are, use /showtick true def. To remove
%  all ticks, use /showtick false def.
%
%  special rule: if x0 and y0 are both exactly zero, then your curve APPENDS
%  an existing path; if not, a new path is begun.
% 

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% EXAMPLE #1
% a plain old curvetrace

gsave 14 55 translate 
10 10 showgrid
[1 1 90   3 7 0   5 4.5 -75  9 2.5 0] curvetrace
0.1 setlinewidth stroke
5 -1 (|2plain stroked curvetrace) cc
grestore


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% EXAMPLE #2
% a plain old curvetrace showing your points for debugging



gsave 14 40 translate 
10 10 showgrid

/showtick true def                   % turn on the ticks   
/ticklen 1 def /tickhead 0.25 def    % set tick size

[1 1 90   3 7 0   5 4.5 -75  9 2.5 0] curvetrace
0.1 setlinewidth stroke
/showtick false def                  % turn ticks back off
5 -1 (|2showing points) cc
grestore


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% EXAMPLE #3
% a curvetrace with a cusp

% a cusp is done by repeating two x and y points having a different entry
% and exit angle. Note how 4,2 repeats here.

gsave 14 25 translate 
10 10 showgrid
[1 6 0 4 2 -90  4 2 90 9 8 0] curvetrace 
0.1 setlinewidth stroke
5 -1 (|2curvetrace with a cusp) cc
grestore



%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% EXAMPLE #4
% variable linewidth curvetracing.

% for variable linewidths, use an "up" path and a "down" path and then fill
% between them. WATCH THE PATH SEQUENCE, OR STRANGE THINGS WILL HAPPEN!

% Your second path should continue from where the first one leaves you and
% end you up back at the beginning.

gsave 14 10 translate 
10 10 showgrid
[1 3 0  4 5 45  9 7 0 
9 7 180  6 5 -135 1 3 180] curvetrace fill
5 -1 (|2double filled curvetrace) cc
grestore


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% EXAMPLE #5
% a filled curvetrace

% All the previous examples have stroked the path. This one fills it instead

gsave 34 55 translate 
10 10 showgrid
[3 7 45 6 6 -45  7 3 -135  4 4 135 3 7 45 ] curvetrace
fill
 5 -1 (|2plain filled curvetrace) cc
grestore



%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% EXAMPLE #6
% curvetraceing inside a path

% The rule: If x0 and y0 are both exactly zero, then the curvetrace APPENDS
% itself to an existing path. If not, a new path is begun

gsave 34 40 translate 
10 10 showgrid 
1 5 mt                                      % start the path
3 pr [0 0 0 5 9 180 6 5 0] curvetrace       % add a curved portion
3 pr                                        % add another straight part
0.3 setlinewidth 1 setlinecap stroke
5 -1 (|2curvetrace inside a path) cc
grestore



%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% EXAMPLE #7
% pipes, braids or wire are done with multiple stroking.

% just use superstroke or superinsidestroke for fancy drawing.

% with superstroke, an array of [ fattestthick fattestgray ....
% thinnestthick thinnestgray] is expected


gsave 34 25 translate 
10 10 showgrid
[2 3 0 8 7 0] curvetrace
1 setlinecap
bestgray 

[0.6 0 0.45 0.9] superstroke      % black 0.6 wide and gray 0.45 wide

 5 -1 (|2pipe or wire) cc 
grestore


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% EXAMPLE #8
% changing the tension.

% an internal parameter called /tension decides how "gung ho" the curve 
% leaves and enters the points. The "best" tension value is usually
% 2.8. Higher tension values make the curvetracing more "rigid" or
% straight-line-like. Negative tension values make the curvetracing
% "looser" or more loopey. Negative tensions go round the other way.

gsave 34 10 translate 
10 10 showgrid
0 setlinewidth
/ctproc {[3 3 90 7 7 0] curvetrace stroke} def  % define a simple curvetrace

/tension 0.48 def ctproc        % so loopey it overshoots
/tension 0.55 def ctproc
/tension 0.7 def ctproc         % really gung ho
/tension 1.0 def ctproc
/tension 1.4 def ctproc
/tension 2.0 def ctproc
/tension 2.8 def ctproc         % normal curve
/tension 6.0 def ctproc         % fairly rigid
/tension 100 def ctproc         % almost straight 
/tension -0.8 def ctproc        % round the other way.

5 -1 (|2changing tension) cc 
grestore


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