A beam tracing approach to acoustic modeling for interactive virtual environments

Abstract

Virtual environment research has focused on interactive image generation and has largely ignored acoustic modeling for spatialization of sound. Yet, realistic auditory cues can complement and enhance visual cues to aid navigation, comprehension, and sense of presence in virtual environments. A primary challenge in acoustic modeling is computation of reverberation paths from sound sources fast enough for real-time auralization. We have developed a system that uses precomputed spatial subdivision and "beam tree" data structures to enable real-time acoustic modeling and auralization in interactive virtual environments. The spatial subdivision is a partition of 3D space into convex polyhedral regions (cells) represented as a cell adjacency graph. A beam tracing algorithm recursively traces pyramidal beams through the spatial subdivision to construct a beam tree data structure representing the regions of space reachable by each potential sequence of transmission and specular reflection events at cell boundaries. From these precomputed data structures, we can generate high-order specular reflection and transmission paths at interactive rates to spatialize fixed sound sources in real-time as the user moves through a virtual environment. Unlike previous acoustic modeling work, our beam tracing method: 1) supports evaluation of reverberation paths at interactive rates, 2) scales to compute highorder reflections and large environments, and 3) extends naturally to compute paths of diffraction and diffuse reflection efficiently. We are using this system to develop interactive applications in which a user experiences a virtual environment immersively via simultaneous auralization and visualization.

Beam Tracing with Refraction

“…Diffuse reflection and diffraction of sound are not currently incorporated in the BTR. These phenomena are already solved with the beam tracing method, and published by several authors (Farina, 2000;Drumm, 2000;Funkhouser et al, 1998;Tsingos, Funkhouser, 2001). The BTR has been specialized to include the refraction.…”

“…Funkhouser et al (1998) presented an implementation of the beam tracing method for interactive auralization of architectural environments. Using spatial data structures, they achieved the performance required for interactive simulation of a moving listener and a stationary source.…”

“…The ending triangle of the beam is the place where the beam leaves the entity, if it is refracted, or the place where the beam is returned back to the entity, if it is reflected. In classical beam tracing, such as the method developed by Drumm (2000) and Funkhouser et al (1998), beams have polygonal cross sections. The advantage of such an approach is that fewer beams are needed to trace a scene than are necessary with triangular beams.…”

Generating Spark Discharge Sound for Interactive Animation using WM-wave

“…Many CG-related studies address such implementations in real time. Procedures have been described for applying the beam tracing method [20][21][22][23][24] and managing acoustic sources by employing clustering [25].…”

The influence of traffic flow dynamics on urban soundscapes

“…The technique used is object precise polygonal beam tracing [35,36]. A beam consists of a group of rays, coherent in space (following about the same path) and bounded by the objects in the simulation area.…”