2dbsplinecurve result 4 2 0 5 1 5 -0.5 -0.5 1 -0.25 0.5 1 0. -0.5 1  0.25 -0.5 1 0.5 -0.5  1
insertknot result 0.5 1
remknot result 2 0 0.01
set length 1.4087044221396998