This is [sketch], an abstraction which lets you draw custom polygons and Bezier curves, useful for designing envelopes and custom waveforms. Unlike other similar objects, [sketch] draws directly into a PD array, so playback is cheap and easy.
This object is very easy to use and very powerful! I hope you enjoy it. Available now in the Context library: https://github.com/LGoodacre/context-sequencer. It needs a few externals, listed in the readme file. Unfortunately, I think it only works in Vanilla for now...