function [col,row,pln] = find_chunk(xq,x,ibeg,iend,a,b,periodic)
  
  if periodic 
    xq = mod(xq-a,b-a)+a;  
  elseif any(xq<a || xq>b)
    error('Query points must be located inside domain.');
  end
  
  x  = reshape(x,[],1);
  xq = reshape(xq,1,[]);
  [~,ii] = min(abs(bsxfun(@minus,x,xq)));
  
  nxq  = numel(xq);
  col = zeros(1,nxq);
  for iq=1:nxq
    col(iq) = find(ii(iq)>=ibeg & ii(iq)<=iend,1,'first');
  end
end