Efficient Subsurface Scattering Simulation for Time-of-Flight Sensors

Abstract

Today, amplitude modulated continuouswave (AMCW) Time-of-Flight (ToF) range cameras are ubiquitous devices that are employed in many fields of application, such as robotics, automotive industry, and home entertainment. Compared to standard RGB cameras, ToF cameras suffer from various error sources related to their fundamental functional principle, such as multipath interference, motion artifacts, or subsurface scattering. Simulating ToF cameras is essential in order to improve future ToF devices or to predict their operability in specific application scenarios. In this paper we present a first simulation approach for ToF cameras that incorporates subsurface scattering effects in semi-transparent media. Subsurface scattering significantly alters the optical path length measured by the ToF camera, leading to erronous phase calculations and, eventually, to wrong range values. We address the challenge to efficiently simulate the superimposed light paths regarding intensity and phase. We address a restricted constellation, i.e., a single semi-transparent layer located on top of an opaque object. Our interactive screen-space AMCW ToF simulation technique incorporates a two-pass light scattering propagation, involving the forward and backward scattering at the interface between air and the semi-transparent object, taking amplitude and phase variations into account. We evaluate our approach by comparing our simulation results to real-world measurements.