function [y q] = fval2(v,p) m = rotation_matrix(v); %q(1) = -v(4)*m(1,1)/m(3,1)-p(1); %q(2) = -v(4)*m(2,1)/m(3,1)-p(2); %q(3) = -v(4)*m(1,2)/m(3,2)-p(3); %q(4) = -v(4)*m(2,2)/m(3,2)-p(4); % x-vanishing point if isinf(p(1)) q(1:2) = [m(1,1)-1 m(2,1)]; else q(1) = v(4)*m(1,1)-p(1,1)*m(3,1); q(2) = v(4)*m(2,1)-p(1,2)*m(3,1); end % y-vanishing point if isinf(p(4)) q(3:4) = [m(1,2) m(2,2)-1]; else q(3) = v(4)*m(1,2)-p(2,1)*m(3,2); q(4) = v(4)*m(2,2)-p(2,2)*m(3,2); end y = dot(q,q);