%% Copyright (c) 2011, INRA
%% 2010-2011, David Legland <david.legland@grignon.inra.fr>
%% 2011 Adapted to Octave by Juan Pablo Carbajal <carbajal@ifi.uzh.ch>
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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);
