function [vx, vy] = getFlow(I1, I2, sigma)
[M11, M12, M22, q1, q2] = getMq(I1, I2, sigma);
% TODO calc flow (w/o loop).
end
function [vx, vy] = getFlow(I1, I2, sigma)
[M11, M12, M22, q1, q2] = getMq(I1, I2, sigma);
% TODO calc flow (w/o loop).
end