linear - piecewise linear segments, as in a polyline.


linear-closed - close the linear segments to form a polygon.


step - alternate between horizontal and vertical segments, as in a step function.


step-before - alternate between vertical and horizontal segments, as in a step function.


step-after - alternate between horizontal and vertical segments, as in a step function.


basis - a B-spline, with control point duplication on the ends.


basis-open - an open B-spline; may not intersect the start or end.


basis-closed - a closed B-spline, as in a loop.


bundle - equivalent to basis, except the tension parameter is used to straighten the spline.


cardinal - a Cardinal spline, with control point duplication on the ends.


cardinal-open - an open Cardinal spline; may not intersect the start or end, but will intersect other control points.


cardinal-closed - a closed Cardinal spline, as in a loop.


monotone - cubic interpolation that preserves monotonicity in y.