Automation

It is possible to change values of some(but not all) controls according to the playback position. This can be achieved by creating automation clips and connecting controls to them.

An AutomationClip contains a series of automation nodes which defines the value of target controls right before/after a node and the time offset of the node from the beginning of the clip. At time points between two nodes, the value is determined by the values of surrounding nodes and interpolation methods(discrete, linear, cubic Hermitian or maybe Bezier curves in the future).

There are some special cases: before the first node, and after the last node. TODO