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Make bundle adjustment deterministic and robust to outliers#5

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deterministic-robust-bundle-adjustment
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Make bundle adjustment deterministic and robust to outliers#5
jasper-tms wants to merge 1 commit into
mainfrom
deterministic-robust-bundle-adjustment

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Bundle adjustment used to be stochastic - each time it runs, it would pull 500 random images out of the dataset and do bundle adjustment on those. If some of the images in the dataset had poor 2D keypoint estimation, the results of bundle adjustment could be wildly different depending on whether the outlier keypoint frames were in or not in the selected 500 images. We make two fixes:

  • Deterministic: Frame subsampling is now seeded. (We also use np.random.choice(replace=False) instead of np.random.randint, which allowed the same frame to be selected multiple times, and silently excluded the last frame).
  • Robust: least_squares now uses loss='soft_l1' with f_scale=8 px so bad 2D detections don't dominate the fit. max_nfev raised from 100 to 500 since the gentler robust gradient needs more iterations to converge.

I need to test this a bit more before confirming that it constitutes a real improvement, but I think it is.

Frame subsampling is now seeded (np.random.default_rng) and uses
np.random.choice(replace=False) instead of np.random.randint, which had
duplicates and silently excluded the last frame. least_squares now uses
loss='soft_l1' with f_scale=8 px so bad 2D detections don't dominate the
fit. max_nfev raised from 100 to 500 since the gentler robust gradient
needs more iterations to converge.
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