function [visible, rho, singular] = h3d_scan_whats_your_view(scan, p)
	% function [visible, rho, singular] = h3d_scan_whats_your_view(scan1, direction)
	%
	% p is a point in the scan's frame of reference
	% We want to know what the scan is seeing in that direction.
	%
	% visible is 1 if it is inside the field of view
	% singular is 1 if more than one point might corrispond to more than one point
	
	
	[tilt, theta, singular]  = h3d_scan_dir2tt(p);
	
	
	thetas = deg2rad(scan.thetas_deg);
	tilts  = deg2rad(scan.tilt_deg);


	% adjust for numerical errors, otherwise unit-tests do not pass
	epsilon = 1e-4;
	thetas(1) = thetas(1)-epsilon;
	thetas(end) = thetas(end)+epsilon;
	tilts(1) = tilts(1)-epsilon;
	tilts(end) = tilts(end)+epsilon;
	

	if (theta < thetas(1)) || (theta > thetas(end)) || (tilt<tilts(1)) || (tilt>tilts(end))
%		fprintf(' %f, %f  not in  [%f,%f] [%f,%f]\n\n', tilt,theta, tilts(1),tilts(end),thetas(1),thetas(end));
		visible = 0;
		rho = NaN;
        return
	end
		
	index_theta = 1 + round( (numel(thetas)-1) * (theta-thetas(1)) / (thetas(end)-thetas(1)));
	index_tilt  = 1 + round( (numel(tilts)-1) * (tilt-tilts(1)) / (tilts(end)-tilts(1)));
	
	
	assert( (index_theta >= 1) && (index_theta <= numel(thetas)));
	assert( (index_tilt >= 1) && (index_tilt <= numel(tilts)));
	
	rho = scan.readings(index_tilt, index_theta);
	visible = 1;