I'm the author, no poo-poo-ing taken. You're completely right. The rendering code is shamelessly unoptimized indeed: doing frustum culling naively actually slows down the code because of the extra draw calls. I could probably get a boost in frame rate--by for instance memcpy-ing chunks into a dynamic buffer and keeping the single draw calls---although it already runs at 300 FPS on the integrated intel card of my laptop. So I'd rather add more features, testing and documentation than worry about perf just yet.