function [value,isterminal,direction] = evntfcn(eta, F)
% [value,isterminal,direction] = evntfcn(eta, F) returns three
% variables used by ode45 to determine when to terminate integration
%
% written by Yuliy Sannikov
global qmax
value = [(qmax - F(3)) F(2) F(4)]; % difference between qmax and q,
% first derivative of theta, first derivative of q
isterminal = [1 1 1]; % terminate computation in all three cases
direction = [0 0 0]; % event occurs whether we get there from above or below