What does an unmodelled principal-point offset cost a self-calibrating bundle adjustment, and does a wide field of view help or hurt?
research/sensing-bapp
A 10 px principal-point offset held at the image centre raises the surface error from 0.0019 to 0.0043 object radii on the wide rig (focal 3.5% off) against 0.0019 to 0.0015 fitted on the narrow one; fitting the point recovers it and removes the cost. Synthetic only
What it found
Takes the next step of sensing-bak2wide. Images are rendered with a true principal-point offset of 0–20 px; one adjustment holds the point at the image centre, the other fits it, both with focal length, k1, k2, poses and points free. On the wide rig (distance 2, f = 400 px) a 10 px offset raises the surface error from 0.0019 to 0.0043 object radii when held (0.0079 at 20 px) and leaves the focal length 3.5% off (10% at 20 px); fitting the point holds 0.0019 throughout and recovers dx to within 0.1 px. The narrow rig is far less sensitive (0.0019 against 0.0015 at 10 px), so a wider view makes the offset matter more. At 2 px of pixel noise the benefit of fitting disappears (0.0083 against 0.0079). dy is pulled toward zero (−7.1 for a true −8). Limits: synthetic, offsets swept not measured, one object, one camera, no tangential distortion, correct matches, 6 seeds.
Paper, code and results
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Produced with AI assistance (Claude). Results are from the code in this repository and are simulated or stylised unless the abstract says otherwise; nothing here implies affiliation with or endorsement by any lab, researcher or company cited. MIT licensed.