Lakulish Antani

RESound: interactive sound rendering for dynamic virtual environments

We present an interactive algorithm and system (RESound) for sound propagation and rendering in virtual environments and media applications. RESound uses geometric propagation techniques for fast computation of propagation paths from a source to a listener and takes into account specular reflections, diffuse reflections, and edge diffraction. In order to perform fast path computation, we use a unified ray-based representation to efficiently trace discrete rays as well as volumetric ray-frusta. RESound further improves sound quality by using statistical reverberation estimation techniques. We also present an interactive audio rendering algorithm to generate spatialized audio signals. The overall approach can render sound in dynamic scenes allowing source, listener, and obstacle motion. Moreover, our algorithm is relatively easy to parallelize on multi-core systems. We demonstrate its performance on complex game-like and architectural environments.

Wave-based sound propagation in large open scenes using an equivalent source formulation

We present a novel approach for wave-based sound propagation suitable for large, open spaces spanning hundreds of meters, with a small memory footprint. The scene is decomposed into disjoint rigid objects. The free-field acoustic behavior of each object is captured by a compact per-object transfer function relating the amplitudes of a set of incoming equivalent sources to outgoing equivalent sources. Pairwise acoustic interactions between objects are computed analytically to yield compact inter-object transfer functions. The global sound field accounting for all orders of interaction is computed using these transfer functions. The runtime system uses fast summation over the outgoing equivalent source amplitudes for all objects to auralize the sound field for a moving listener in real time. We demonstrate realistic acoustic effects such as diffraction, low-passed sound behind obstructions, focusing, scattering, high-order reflections, and echoes on a variety of scenes.

FastV: from-point visibility culling on complex models

We present an efficient technique to compute the potentially visible set (PVS) of triangles in a complex 3D scene from a viewpoint. The algorithm computes a conservative PVS at object space accuracy. Our approach traces a high number of small, volumetric frusta and computes blockers for each frustum using simple intersection tests. In practice, the algorithm can compute the PVS of CAD and scanned models composed of millions of triangles at interactive rates on a multi‐core PC. We also use the visibility algorithm to accurately compute the reflection paths from a point sound source. The resulting sound propagation algorithm is 10–20X faster than prior accurate geometric acoustic methods.

Wave-ray coupling for interactive sound propagation in large complex scenes

We present a novel hybrid approach that couples geometric and numerical acoustic techniques for interactive sound propagation in complex environments. Our formulation is based on a combination of spatial and frequency decomposition of the sound field. We use numerical wave-based techniques to precompute the pressure field in the near-object regions and geometric propagation techniques in the far-field regions to model sound propagation. We present a novel two-way pressure coupling technique at the interface of near-object and far-field regions. At runtime, the impulse response at the listener position is computed at interactive rates based on the stored pressure field and interpolation techniques. Our system is able to simulate high-fidelity acoustic effects such as diffraction, scattering, low-pass filtering behind obstruction, reverberation, and high-order reflections in large, complex indoor and outdoor environments and Half-Life 2 game engine. The pressure computation requires orders of magnitude lower memory than standard wave-based numerical techniques.

Interactive sound propagation using compact acoustic transfer operators

We present an interactive sound propagation algorithm that can compute high orders of specular and diffuse reflections as well as edge diffractions in response to moving sound sources and a moving listener. Our formulation is based on a precomputed acoustic transfer operator, which we compactly represent using the Karhunen-Loeve transform. At runtime, we use a two-pass approach that combines acoustic radiance transfer with interactive ray tracing to compute early reflections as well as higher-order reflections and late reverberation. The overall approach allows accuracy to be traded off for improved performance at runtime, and has a low memory overhead. We demonstrate the performance of our algorithm on different scenarios, including an integration of our algorithm with Valves Source game engine.

Direct-to-Indirect Acoustic Radiance Transfer

We present an efficient algorithm for simulating diffuse reflections of sound in a static scene. Our approach is built on recent advances in precomputed light transport techniques for visual rendering and uses them to develop an improved acoustic radiance transfer technique. We precompute a direct-to-indirect acoustic transfer operator for a scene, and use it to map direct sound incident on the surfaces of the scene to multibounce diffuse indirect sound, which is gathered at the listener to compute the final impulse response. Our algorithm decouples the transfer operator from the source position so we can efficiently update the acoustic response at the listener when the source moves. We highlight its performance on various benchmarks and observe significant speedups over prior methods based on acoustic radiance transfer.

Source and Listener Directivity for Interactive Wave-Based Sound Propagation

We present an approach to model dynamic, data-driven source and listener directivity for interactive wave-based sound propagation in virtual environments and computer games. Our directional source representation is expressed as a linear combination of elementary spherical harmonic (SH) sources. In the preprocessing stage, we precompute and encode the propagated sound fields due to each SH source. At runtime, we perform the SH decomposition of the varying source directivity interactively and compute the total sound field at the listener position as a weighted sum of precomputed SH sound fields. We propose a novel plane-wave decomposition approach based on higher-order derivatives of the sound field that enables dynamic HRTF-based listener directivity at runtime. We provide a generic framework to incorporate our source and listener directivity in any offline or online frequency-domain wave-based sound propagation algorithm. We have integrated our sound propagation system in Valves Source game engine and use it to demonstrate realistic acoustic effects such as sound amplification, diffraction low-passing, scattering, localization, externalization, and spatial sound, generated by wave-based propagation of directional sources and listener in complex scenarios. We also present results from our preliminary user study.

Aural Proxies and Directionally-Varying Reverberation for Interactive Sound Propagation in Virtual Environments

We present an efficient algorithm to compute spatially-varying, direction-dependent artificial reverberation and reflection filters in large dynamic scenes for interactive sound propagation in virtual environments and video games. Our approach performs Monte Carlo integration of local visibility and depth functions to compute directionally-varying reverberation effects. The algorithm also uses a dynamically-generated rectangular aural proxy to efficiently model 2-4 orders of early reflections. These two techniques are combined to generate reflection and reverberation filters which vary with the direction of incidence at the listener. This combination leads to better sound source localization and immersion. The overall algorithm is efficient, easy to implement, and can handle moving sound sources, listeners, and dynamic scenes, with minimal storage overhead. We have integrated our approach with the audio rendering pipeline in Valves Source game engine, and use it to generate realistic directional sound propagation effects in indoor and outdoor scenes in real-time. We demonstrate, through quantitative comparisons as well as evaluations, that our approach leads to enhanced, immersive multi-modal interaction.

Fast and Accurate Geometric Sound Propagation Using Visibility Computations

Geometric Acoustics (GA) techniques based on the image-source method, ray tracing, beam tracing, and ray-frustum tracing, are widely used to compute sound propagation paths. In this paper, we highlight the connection between these propagation techniques with the research on visibility computation in computer graphics and computational geometry. We give a brief overview of visibility algorithms and apply some of these methods to accelerate GA, specifically early specular reflections and finite-edge diffraction. Moreover, we survey our recent work on fast and accurate GA methods that use accurate and conservative visibility techniques. This includes: a) an algorithm for fast computation of early specular reflections using conservative from-point visibility computation; and b) a fast method for finite-edge diffraction using conservative from-region visibility computation. Our approach for computing specular reflections is based on the image-source method and we reduce the number of image sources by using conservative visibility computations. The edge diffraction computation is based on the well known Biot-Tolstoy-Medwin (BTM) diffraction model and we combine it with efficient algorithms for region-based visibility to significantly reduce the number of edge pairs that need to be processed for higher-order diffraction computation. We highlight the performance of these methods on many complex models. Our initial results indicate that we obtain considerable speedups over prior methods for accurate geometric sound propagation.

Validation of adaptive rectangular decomposition for three-dimensional wave-based acoustic simulation in architectural models

Computer-based simulation is an increasingly popular way to predict the acoustics of real-world architectural designs. Most commercial acoustic simulation tools are based on geometric techniques and cannot accurately model low-frequency diffraction and other wave phenomena. Numerical wave simulation techniques can model these effects, but are less commonly used, since they are compute- and memory-intensive, and cannot scale to large spaces. Moreover, it is challenging to ensure that numerical methods do not suffer from high dispersion errors. Recent techniques have begun to overcome these limitations. One such method is adaptive rectangular decomposition (ARD), which combines analytical solutions to the wave equation in rectangular subdomains with a finite difference stencil for interface handling between subdomains, resulting in high-performance wave simulation with low dispersion error. ARD, along with high-performance ray tracing, are available as part of Impulsonic’s IPL SDK, a software development ki...