kernel density is important

Hmm, interesting thought. My original surf algorithm was to check every point along the second wave (in the days of bins and no precise intersection), but just checking forward/stop/reverse somehow always outperformed it. It's true that a lot has changed since then, including bullet shadows, so maybe you're right. But my most recent experiments with changing my surf algorithm were even more significant and came out with almost no change in score, so now I'm a little skeptical about tweaking my surf algorithm. =)