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%%%% prbla_12.ldf
%%%% Created by Laurence D. Finston (LDF) Mon Nov 21 21:56:33 CET 2005
%% * (1) Copyright and License.
%%%% This file is part of GNU 3DLDF, a package for three-dimensional drawing.
%%%% Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 The Free Software Foundation
%%%% GNU 3DLDF 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 of the License, or
%%%% (at your option) any later version.
%%%% GNU 3DLDF 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 GNU 3DLDF; if not, write to the Free Software
%%%% Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
%%%% GNU 3DLDF is a GNU package.
%%%% It is part of the GNU Project of the
%%%% Free Software Foundation
%%%% and is published under the GNU General Public License.
%%%% See the website http://www.gnu.org
%%%% for more information.
%%%% GNU 3DLDF is available for downloading from
%%%% http://www.gnu.org/software/3dldf/LDF.html.
%%%% Please send bug reports to Laurence.Finston@gmx.de
%%%% The mailing list help-3dldf@gnu.org is available for people to
%%%% ask other users for help.
%%%% The mailing list info-3dldf@gnu.org is for the maintainer of
%%%% GNU 3DLDF to send announcements to users.
%%%% To subscribe to these mailing lists, send an
%%%% email with ``subscribe <email-address>'' as the subject.
%%%% The author can be contacted at:
%%%% Laurence D. Finston
%%%% c/o The Free Software Foundation, Inc.
%%%% 51 Franklin St, Fifth Floor
%%%% Boston, MA 02110-1301
%%%% USA
%%%% Laurence.Finston@gmx.de
%% Run these commands:
%% 3dldf prbla_12.ldf
%% mpost prbla_12
%% tex prbla_12.txt
%% dvips -o prbla_12.ps prbla_12.dvi
%% gv prbla_12.ps &
%% ** (2) The intersection of a `parabola' and linear `paths' that do
%% not lie in the same plane as the `parabola'.
%% LDF 2005.11.21.
picture axis_picture;
%% **** (4) axis_picture.
beginfig(0);
pickup pencircle scaled (1mm, 1mm);
axis_x_lft := 5;
axis_x_rt := 15;
axis_y_bot := 10;
axis_y_top := 10;
axis_z_front := 7;
axis_z_back := 10;
drawarrow origin -- (-axis_x_lft, 0);
drawarrow origin -- (axis_x_rt, 0);
label.bot("x", (axis_x_rt, 0, -.1));
drawarrow origin -- (0, -axis_y_bot);
drawarrow origin -- (0, axis_y_top);
label.lft("y", (0, axis_y_top));
drawarrow origin -- (0, 0, -axis_z_front);
drawarrow origin -- (0, 0, axis_z_back);
label.lft("z", (-.25, 0, axis_z_back));
axis_picture := current_picture;
clear current_picture;
endfig;
verbatim_metapost "verbatimtex \magnification=\magstep5 \font\large=cmr12 etex";
focus f;
set f with_position (-5, 10, -20) with_direction (-5, 10, 100) with_distance 15;
pickup pencircle scaled (.75mm, .75mm);
beginfig(1);
parabola prb[];
point p[];
set prb0 with_parameter 3 with_extent 12;
p0 := get_point 3 prb0;
p1 := p0 shifted (3, 5, 3);
p2 := mediate(p1, p0, 2);
path q[];
q0 := p2 -- p1;
q1 := q0 rotated (-15, 30) shifted (15, 0, -1);
draw q0;
draw q1;
draw prb0 with_color red;
output axis_picture with_focus f no_sort;
output current_picture with_focus f no_sort;
clear current_picture;
%% **** (4)
verbatim_metapost "pickup pencircle scaled .75mm";
bool_point_vector bpv;
bpv := prb0 intersection_points q0;
message "bpv:";
show bpv;
if size bpv > 0:
dotlabel.ulft("$i_0$", bpv0) with_dot_color blue;
fi;
clear bpv; %% This shouldn't be necessary! Fix it. LDF 2005.11.21.
bpv := prb0 intersection_points q1;
message "bpv:";
show bpv;
if size bpv > 0:
dotlabel.urt("$i_1$", bpv0) with_dot_color blue;
fi;
endfig with_focus f no_sort;
verbatim_metapost "end";
end;
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