Approximate diffraction modeling for real-time sound propagation simulation

Abstract

Convincing simulation of diffraction around obstacles is critical in modeling sound propagation in virtual environments. Due to the computational complexity of large-scale wavefield simulations, ray-based models of diffraction are used in real-time interactive multimedia applications. Among popular diffraction models, the Biot-Tolstoy-Medwin (BTM) edge diffraction model is the most accurate, but it suffers from high computational complexity and hence is difficult to apply in real time. This paper introduces an alternative ray-based approach to approximating diffraction, called Volumetric Diffraction and Transmission (VDaT). VDaT is a volumetric diffraction model, meaning it performs spatial sampling of paths along which sound can traverse the scene around obstacles. VDaT uses the spatial sampling results to estimate the BTM edge-diffraction amplitude response and path length, with a much lower computational cost than computing BTM directly. On average, VDaT matches BTM results within 1–3 dB over a wide range of size scales and frequencies in basic cases, and VDaT can handle small objects and gaps better than comparable state-of-the-art real-time diffraction implementations. A GPU-parallelized implementation of VDaT is shown to be capable of simulating diffraction on thousands of direct and specular reflection path segments in small-to-medium-size scenes, within strict real-time constraints and without any precomputed scene information.

Fast diffraction pathfinding for dynamic sound propagation

“…The recent diffraction approach of Pisha et al [2020] reports performance that is comparable to ours. However, their approach was tested on low complexity scenes (≤ 1024 triangles), and uses a powerful GPU for ray tracing.…”

“…Since we use the UTD diffraction model to calculate diffraction path intensities, our approach has all of the limitations of UTD such as inaccuracy with small edges. However, other more-accurate diffraction models like BTM or [Pisha et al 2020] could be used in place of UTD to ameliorate some of these issues. Another limitation is that the diffraction graph traversal algorithm only finds a single path per edge, though this nevertheless produces plausible results.…”

“…In contrast, our technique is applicable to scenes that are more than 1000× larger, and runs on a single thread of a modest CPU. Despite this, its good agreement with BTM makes [Pisha et al 2020] an attractive replacement for UTD evaluation of the diffracted sound pressure in our approach.…”

“…Cowan et al [2015] proposed an ad-hoc 2D rasterization-based method for approximating occlusion that compares the diffracted path length to the straight-line distance between the source and listener. Recently, Pisha et al [2020] described a diffraction model that uses a dense volumetric sampling of rays around existing direct and reflected propagation path segments to approximate the BTM magnitude response.…”

A Universal Filter Approximation of Edge Diffraction for Geometrical Acoustics

“…For acoustics simulation of in indoor and urban outdoor environments, geometrical acoustics (GA), assuming ray-like sound propagation, offer advantages with regard computational complexity [12]- [14] and have become a de-facto standard. Effects of diffraction can be included in GA by constructing sound ray propagation paths involving "bending" at edges [15] like building or room corners, or at the boundaries of smaller objects, like boards or plates [16]- [19].…”