Coincidentally, I recently put up a profile coffee roasting planner built on cubic splines. The constraints of the cubic spline match up nicely with the behavior of coffee in a roasting machine so doing it this way gets you plans that are easy to follow and fast to put together or edit. This one is just done as a web site, but prior to that I'd been using a prototype in C++ (unreleased because no UI) for several years. Try not to look at the code too closely, not a web dev. https://crucs.net.