Simple from-scratch implementation of splines via-nodes w/ incoming- and outgoing- handles.
It forms a series of pairs of line-segments, where the first segment is from Node1 to OutgoingHandle1, and the second segment is IncomingHandle2 to Node2. It then draws a curve between these two segments interpolating between them. Cosine is used as the interpolation function so that the curves are tangent to the handles at the nodes, but I'm not crazy about how it looks. Possible sqrt(cosine) might look better.