Virtual Light Transport Matrices for Non-Line-Of-Sight Imaging
This work addresses the challenge of extending light transport techniques to NLOS scenarios, which is incremental as it adapts existing line-of-sight methods to a new domain.
The paper tackles the problem of estimating light transport matrices for non-line-of-sight (NLOS) imaging, enabling applications like relighting and illumination separation in hidden scenes, with results demonstrating the ability to separate direct, first-order indirect, and higher-order indirect illumination in complex cluttered scenes.
The light transport matrix (LTM) is an instrumental tool in line-of-sight (LOS) imaging, describing how light interacts with the scene and enabling applications such as relighting or separation of illumination components. We introduce a framework to estimate the LTM of non-line-of-sight (NLOS) scenarios, coupling recent virtual forward light propagation models for NLOS imaging with the LOS light transport equation. We design computational projector-camera setups, and use these virtual imaging systems to estimate the transport matrix of hidden scenes. We introduce the specific illumination functions to compute the different elements of the matrix, overcoming the challenging wide-aperture conditions of NLOS setups. Our NLOS light transport matrix allows us to (re)illuminate specific locations of a hidden scene, and separate direct, first-order indirect, and higher-order indirect illumination of complex cluttered hidden scenes, similar to existing LOS techniques.