2dbeziercurve b1  8  0 0 0 1 -2 1 -2 -3 4 -3 4 5 -6 5 -6 -4
trim b2 b1 0 0.2
trim b3 b1 0.3 0.5
trim result b1 0.6 0.8
checklength result -l 3.3427826104791247