/usr/share/octave/packages/geometry-1.7.0/geom2d/clipRay.m is in octave-geometry 1.7.0-1build1.
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## Copyright (C) 2004-2011 INRA - CEPIA Nantes - MIAJ (Jouy-en-Josas)
## Copyright (C) 2012 Adapted to Octave by Juan Pablo Carbajal <carbajal@ifi.uzh.ch>
## All rights reserved.
##
## Redistribution and use in source and binary forms, with or without
## modification, are permitted provided that the following conditions are met:
##
## 1 Redistributions of source code must retain the above copyright notice,
## this list of conditions and the following disclaimer.
## 2 Redistributions in binary form must reproduce the above copyright
## notice, this list of conditions and the following disclaimer in the
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##
## THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ''AS IS''
## AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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## ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
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## -*- texinfo -*-
## @deftypefn {Function File} {[@var{edge} @var{inside}] =} clipRay (@var{ray}, @var{box})
## Clip a ray with a box.
##
## @var{ray} is a straight ray given as a 4 element row vector: [x0 y0 dx dy],
## with (x0 y0) being the origin of the ray and (dx dy) its direction
## vector, @var{box} is the clipping box, given by its extreme coordinates:
## [xmin xmax ymin ymax].
## The result is given as an edge, defined by the coordinates of its 2
## extreme points: [x1 y1 x2 y2].
## If the ray does not intersect the box, [NaN NaN NaN NaN] is returned.
##
## Function works also if @var{ray} is a Nx4 array, if @var{box} is a Nx4 array, or
## if both @var{ray} and @var{box} are Nx4 arrays. In these cases, @var{edge} is a Nx4
## array.
##
## @seealso{rays2d, boxes2d, edges2d, clipLine, drawRay}
## @end deftypefn
function [edge isInside] = clipRay(ray, bb)
# adjust size of two input arguments
if size(ray, 1)==1
ray = repmat(ray, size(bb, 1), 1);
elseif size(bb, 1)==1
bb = repmat(bb, size(ray, 1), 1);
elseif size(ray, 1) != size(bb, 1)
error('bad sizes for input');
end
# first compute clipping of supporting line
edge = clipLine(ray, bb);
# detectes valid edges (edges outside box are all NaN)
inds = find(isfinite(edge(:, 1)));
# compute position of edge extremities relative to the ray
pos1 = linePosition(edge(inds,1:2), ray(inds,:));
pos2 = linePosition(edge(inds,3:4), ray(inds,:));
# if first point is before ray origin, replace by origin
edge(inds(pos1<0), 1:2) = ray(inds(pos1<0), 1:2);
# if last point of edge is before origin, set all edge to NaN
edge(inds(pos2<0), :) = NaN;
# eventually returns result about inside or outside
if nargout>1
isInside = isfinite(edge(:,1));
end
endfunction
%!shared bb
%! bb = [0 100 0 100];
%!test # inside
%! origin = [30 40];
%! direction = [10 0];
%! ray = [origin direction];
%! expected = [30 40 100 40];
%! assert (expected, clipRay(ray, bb), 1e-6);
%!test # outside
%! origin = [30 140];
%! direction = [10 0];
%! ray = [origin direction];
%! assert (sum(isnan(clipRay(ray, bb)))==4);
%!test # line inside, but ray outside
%! origin = [130 40];
%! direction = [10 0];
%! ray = [origin direction];
%! assert (sum(isnan(clipRay(ray, bb)))==4);
%!test # inside
%! origin = [30 40];
%! direction = [-10 0];
%! ray = [origin direction];
%! expected = [30 40 0 40];
%! assert (expected, clipRay(ray, bb), 1e-6);
%!test # outside
%! origin = [30 140];
%! direction = [-10 0];
%! ray = [origin direction];
%! assert (sum(isnan(clipRay(ray, bb)))==4);
%!test # line inside, but ray outside
%! origin = [-30 40];
%! direction = [-10 0];
%! ray = [origin direction];
%! assert (sum(isnan(clipRay(ray, bb)))==4);
%!test # inside
%! origin = [30 40];
%! direction = [0 10];
%! ray = [origin direction];
%! expected = [30 40 30 100];
%! assert (expected, clipRay(ray, bb), 1e-6);
%!test # outside
%! origin = [130 40];
%! direction = [0 10];
%! ray = [origin direction];
%! assert (sum(isnan(clipRay(ray, bb)))==4);
%!test # line inside, but ray outside
%! origin = [30 140];
%! direction = [0 10];
%! ray = [origin direction];
%! assert (sum(isnan(clipRay(ray, bb)))==4);
%!test # inside
%! origin = [30 40];
%! direction = [0 -10];
%! ray = [origin direction];
%! expected = [30 40 30 0];
%! assert (expected, clipRay(ray, bb), 1e-6);
%!test # outside
%! origin = [130 40];
%! direction = [0 -10];
%! ray = [origin direction];
%! assert (sum(isnan(clipRay(ray, bb)))==4);
%!test # line inside, but ray outside
%! origin = [30 -40];
%! direction = [0 -10];
%! ray = [origin direction];
%! assert (sum(isnan(clipRay(ray, bb)))==4);
%!test
%! origins = [30 40;30 40;30 140;130 40];
%! directions = [10 0;0 10;10 0;0 10];
%! rays = [origins directions];
%! expected = [30 40 100 40;30 40 30 100;NaN NaN NaN NaN;NaN NaN NaN NaN];
%! clipped = clipRay(rays, bb);
%! assert (expected, clipped, 1e-6);
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