function [edge, isInside] = clipRay(ray, bb)
%CLIPRAY Clip a ray with a box.
%
%   EDGE = clipRay(RAY, BOX);
%   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, 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 RAY is a N-by-4 array, if BOX is a Nx4 array, or
%   if both RAY and BOX are N-by-4 arrays. In these cases, EDGE is a N-by-4
%   array.
%      
%   See also 
%     rays2d, boxes2d, edges2d, clipLine, drawRay
%

% ------
% Author: David Legland
% E-mail: david.legland@inrae.fr
% Created: 2010-05-13, using Matlab 7.4.0.287 (R2007a)
% Copyright 2010-2022 INRA - Cepia Software Platform

% 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);

% detects 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,:), 'diag');
pos2 = linePosition(edge(inds,3:4), ray(inds,:), 'diag');

% 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
