After completing the basic design and software for the whiteboard drawing bot, I decided to make an interactive simulator and shape editor to allow people to generate their own commands. I thought it would be cool to share it as well, in case other people wanted to play with the stroking/filling algorithms or use it to run their own drawing robots or do something else with it entirely.
For the simulator, I wrote a parser to parse the command sequence, and then animated it drawing the command out onto the screen. The parser is written with PEG.js, which I'll be discussing a bit later. The parameters for the generation and rendering are controlled using DAT.gui, and the drawing itself is done using two layered canvases: the bottom one to hold the actual drawing that persists from frame to frame, and the top one to render the arms, which are cleared and redrawn each frame. I separated them because I did not want to have to re-render the entire drawing each time the simulator drew anything new.