%%%% elpsd_13.ldf %%%% Created by Laurence D. Finston (LDF) Fri Dec 9 21:41:57 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, 2014, 2015, 2016, 2017, 2018, 2019, 2020, 2021, 2022, 2023 The Free Software Foundation, Inc. %%%% 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 '' 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 %% *** (3) The intersection points of a linear `path' and an `ellipsoid'. %% LDF 2005.12.09. verbatim_metapost "verbatimtex \magnification=\magstep5 etex"; pickup pencircle scaled (.75mm, .75mm); focus f; set f with_position (-10, 15, -30) with_direction (-10, 15, 100) with_distance 20; picture save_picture; beginfig(1); transform t; %t := identity rotated (15, 15) shifted (1, 1, 1); t := identity; ellipsoid e; set e with_center origin with_axis_x 20 with_axis_y 16 with_axis_z 10 with_divisions_x 6 with_divisions_y 6 with_divisions_z 2 with_point_count 64; e *= t; draw e; % cuboid c; % c := out_cuboid e; % draw c with_color red; path q[]; q0 := ((-10, -10) -- (10, 10)) rotated -90 shifted (0, 1); %q0 := (0, -10) -- (0, 10); q0 *= t; draw q0 with_color blue; bool_point_vector bpv; bpv := e intersection_points q0; message "bpv:"; show bpv; point p[]; p0 := bpv0; p1 := bpv1; message "p0 location e:"; show p0 location e; drawdot bpv0 with_color green with_pen pencircle scaled (1.5mm, 1.5mm); label.top("$i_0$", p0 shifted (0, .2)); drawdot bpv1 with_color green with_pen pencircle scaled (1.5mm, 1.5mm); label.lrt("$i_1$", p1 shifted (0, .2)); save_picture := current_picture; label("Perspective Projection", (0, -11)); endfig with_focus f no_sort; %end; point label_pt; label_pt := (0, -10); beginfig(2); output save_picture with_projection parallel_x_z; label("Parallel Projection, X-Z Plane", label_pt); endfig with_projection parallel_x_y; beginfig(3); output save_picture with_projection parallel_x_y; label("Parallel Projection, X-Y Plane", label_pt); endfig with_projection parallel_x_y; beginfig(4); output save_picture with_projection parallel_z_y; label("Parallel Projection, Z-Y Plane", label_pt); endfig with_projection parallel_x_y; verbatim_metapost "end"; end;