The outline's corners in order; the last joins back to the first.
OptionalradiusThe radius every corner is rounded with; 0 leaves corners sharp.
OptionalradiusA radius per corner, in the order of points, used instead of radius when given.
OptionalsegmentsHow many straight pieces draw a quarter turn of arc; a smaller turn takes fewer.
A flat outline and the arcs
polyline.roundCorners2drounds its corners with.