Seeing Tree Structure from Vibration
This addresses a specific challenge in computer vision for scenarios like analyzing trees or vessels where traditional cues fail, but it is incremental in combining existing methods.
The paper tackled the problem of recognizing hierarchical tree structure from videos when appearance and motion signals are ambiguous, by using spectral analysis of vibrations and nonparametric Bayesian inference, achieving good performance on real-world videos of trees and vessels.
Humans recognize object structure from both their appearance and motion; often, motion helps to resolve ambiguities in object structure that arise when we observe object appearance only. There are particular scenarios, however, where neither appearance nor spatial-temporal motion signals are informative: occluding twigs may look connected and have almost identical movements, though they belong to different, possibly disconnected branches. We propose to tackle this problem through spectrum analysis of motion signals, because vibrations of disconnected branches, though visually similar, often have distinctive natural frequencies. We propose a novel formulation of tree structure based on a physics-based link model, and validate its effectiveness by theoretical analysis, numerical simulation, and empirical experiments. With this formulation, we use nonparametric Bayesian inference to reconstruct tree structure from both spectral vibration signals and appearance cues. Our model performs well in recognizing hierarchical tree structure from real-world videos of trees and vessels.