In progress · monocular camera

Rigid and non-rigid motion

Detecting and 3-D-tracking rigid and non-rigid objects from a single moving camera.

Status

Active work at the University of Waterloo VIP Lab. No manuscript submitted, and no benchmark numbers are quoted on this page. What follows is the problem and the approach, not a results claim.

The problem

A camera on a moving platform sees a scene in which everything moves at once: the camera, the target, and the background. Recovering what the target is doing means separating three motions that arrive superimposed in a single 2-D image stream, with no stereo baseline and no active depth sensor to fall back on.

Rigid targets and non-rigid ones fail differently. A rigid body’s motion can be explained by one transform; a deforming body cannot, and a pipeline that assumes rigidity will quietly mis-attribute deformation to translation.

The approach

A multi-cue pipeline, each cue covering a different failure mode of the others:

Cues fused in the pipeline
CueWhat it contributes
Dense optical flow (RAFT)2-D correspondence between consecutive frames
Optical expansionChange in apparent size, the depth-rate signal flow alone cannot give
Monocular metric depth (Metric3D)Absolute scale, so velocities come out in metres per second

Fusing these yields, per target, an estimate of depth, velocity, time-to-collision, and a 3-D intercept solution, from one camera.

Why it matters

The same constraint drives the counter-UAV work: when the platform moves, the motion cue that makes a small target visible is exactly the cue that camera ego-motion destroys. That paper solved a narrow version of the problem: detection, in thermal, with flow channels. This is the general version, in 3-D.