Since the filter bank approach is taking too long to run and the result is not impressive, I am playing with the old algorithm with a lot more samples. The sample size is 170 (instead of 30 originally) and blue stars are those negative samples. I think the histogram approach is good for determining "what is this" rather than "what is not". The older implementation just check if the distance is far enough for those negative samples. This time I check if the window and negative samples are close enough, and then reject the window if it is true.
However the red stars at the upper middle of the image is just a big block of mud. I have 3 negative samples to account for that region but it just does not work out.
UCSD CSE190a Haili Wang