12dbsplinecurve 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 2insertknot result 0.5 1 3remknot result 2 0 0.01 4checklength result -l 1.4087044221396998 5