Motion and Structure from Event-based Normal Flow

Kavli Affiliate: Yi Zhou

| First 5 Authors: Zhongyang Ren, Bangyan Liao, Delei Kong, Jinghang Li, Peidong Liu

| Summary:

Recovering the camera motion and scene geometry from visual data is a
fundamental problem in the field of computer vision. Its success in standard
vision is attributed to the maturity of feature extraction, data association
and multi-view geometry. The recent emergence of neuromorphic event-based
cameras places great demands on approaches that use raw event data as input to
solve this fundamental problem. Existing state-of-the-art solutions typically
infer implicitly data association by iteratively reversing the event data
generation process. However, the nonlinear nature of these methods limits their
applicability in real-time tasks, and the constant-motion assumption leads to
unstable results under agile motion. To this end, we rethink the problem
formulation in a way that aligns better with the differential working principle
of event cameras. We show that the event-based normal flow can be used, via the
proposed geometric error term, as an alternative to the full flow in solving a
family of geometric problems that involve instantaneous first-order kinematics
and scene geometry. Furthermore, we develop a fast linear solver and a
continuous-time nonlinear solver on top of the proposed geometric error term.
Experiments on both synthetic and real data show the superiority of our linear
solver in terms of accuracy and efficiency, and indicate its complementary
feature as an initialization method for existing nonlinear solvers. Besides,
our continuous-time non-linear solver exhibits exceptional capability in
accommodating sudden variations in motion since it does not rely on the
constant-motion assumption.

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