Inferring "Dark Matter" and "Dark Energy" from Videos

Dan Xie, Sinisa Todorovic, Song-Chun Zhu; Proceedings of the IEEE International Conference on Computer Vision (ICCV), 2013, pp. 2224-2231

This paper presents an approach to localizing functional objects in surveillance videos without domain knowledge about semantic object classes that may appear in the scene. Functional objects do not have discriminative appearance and shape, but they affect behavior of people in the scene. For example, they "attract" people to approach them for satisfying certain needs (e.g., vending machines could quench thirst), or "repel" people to avoid them (e.g., grass lawns). Therefore, functional objects can be viewed as "dark matter", emanating "dark energy" that affects people's trajectories in the video. To detect "dark matter" and infer their "dark energy" field, we extend the Lagrangian mechanics. People are treated as particle-agents with latent intents to approach "dark matter" and thus satisfy their needs, where their motions are subject to a composite "dark energy" field of all functional objects in the scene. We make the assumption that people take globally optimal paths toward the intended "dark matter" while avoiding latent obstacles. A Bayesian framework is used to probabilistically model: people's trajectories and intents, constraint map of the scene, and locations of functional objects. A data-driven Markov Chain Monte Carlo (MCMC) process is used for inference. Our evaluation on videos of public squares and courtyards demonstrates our effectiveness in localizing functional objects and predicting people's trajectories in unobserved parts of the video footage.