I’ve combed through enough of Wilba’s code to understand the fundamentals. I’ve done some cleanup and added comments and a bit of debugging functionality. I’ve uploaded the latest updates to github.
Searching the web for drawbot stuff I came across a post by Wilba on XKCD’s forum with some pictures and comments describing his drawbot geometry. This was a big help when trying to understand the code.
Wilba’s drawbot code supports using a larger spool and calculating the tangent point of the cord from the spool when calculating the pen position. The drawbot I’m making is much simpler. I’m using fishing line through an eyelet which fixes the cord origin regardless of the spool diameter or angle to the pen. Using a string around a spool does have the issue of the spool diameter changing due to wrap up of the string around the spool, but I’m using fishing line on a reasonably sized spool so the diameter change should be small.
At this point I’m going to fork the code from DrawbotWilba to DrawbotOne. DrawbotOne will be simpler to start with since it will only support the cord entering the drawing space from a fixed point at the eyelet.