Volume 0 (1981), Number 0 pp. 1–8 COMPUTER GRAPHICS forum Sound Tracing: Rendering Listener Specific Acoustic Room Properties Jens Bellmann 1 , Frank Michel 2 , Eduard Deines 2 , Martin Hering-Bertram 3 , Jan Mohring 3 , and Hans Hagen 1 1 Computer Science Department, University of Kaiserslautern, Germany 2 International Research Training Group (IRTG), Kaiserslautern, Germany 3 Fraunhofer Institut Techno- und Wirtschaftsmathematik (ITWM) Abstract We present an acoustic rendering approach visualizing the listener-specific contribution of frequency-dependent pressure fields on a scene geometry with acoustic reflection and scattering properties. Our method facilitates the evaluation of simulated acoustics showing the effect of simulation parameters like absorption and scatter- ing. The image-based spatial localization of acoustic properties is complementary to the auditive evaluation by means of auralization. Our core contribution is a pressure-based acoustic rendering equation and a corresponding raytracing method applying techniques from photorealistic rendering to the field of simulated room acoustics. Ap- plications are directed at the visualization of interference patterns and analyzing the impact of acoustic reflection parameters. Categories and Subject Descriptors (according to ACM CCS): I.3.7 [Computer Graphics]: Three-Dimensional Graphics and RealismRaytracing; I.6.8 [Simulation and Modeling]: Types of Simulation Monte Carlo; J.2 [Com- puter Applications]: Physical Sciences and EngineeringPhysics 1. Motivation Understanding the results of numerical simulation is a pri- mary goal of scientific visualization. In the scope of simu- lated acoustics, the most general concept is a virtual-reality (VR) based combination of visualization and auralization methods [FCE + 98, BDM + 05, LSVA07]. This means that stereoscopic viewing of three-dimensional geometry and si- multaneous display of acoustic signals within an immersive VR-environment is feasible. Auralization systems provide a realistic auditive environment, either using a great number of speakers for sound field synthesis or based on head-related transfer functions providing stereo signals perceived by a hu- man. The core contribution of the present work to this process is the adaption of photo-realistic rendering techniques to the visualization of acoustic simulation results. Therefore, we establish a pressure based acoustic rendering equation which is applied to an array of frequencies. Since the auditive en- vironment of a scene is by far more complex than its visual environment regarding the number of base frequencies that can be distinguished, our method produces a set of images in each rendering pass. For each frequency, the corresponding image conveys the pressure amplitude (mapped to bright- ness) and its phase shift (mapped to color). From this vi- sual representation, local details of the directional impulse response are conveyed spatially much sharper than possible with auditive methods, complementing the valuable analysis by means of auralization. While methods inspired by photo-realistic rendering [JC98] have already been used for acoustic simulation [KJM04, BDM + 05], to our knowledge there exists no ap- proach of this kind for visualization purposes. Instead, pre- vious work on acoustic visualization is mostly based on graphical primitives like spheres, arrows and (iso-)surfaces, whereas rendering plays an inferior role. Theoretical ap- proaches well known from photo-realistic image synthesis, e.g. approaches based on a rendering equation [Kaj86], have not yet been used for the visual evaluation of acoustic sim- ulation results. The present work is meant to close this gap, showing that acoustic environments provide a “nice and col- orful view” when seen with the eyes. This enables us to un- derstand the contribution of reflected and direct sound to the audible result at a special position in an intuitive way, be- c  2008 The Author(s) Journal compilation c 2008 The Eurographics Association and Blackwell Publishing Ltd. Published by Blackwell Publishing, 9600 Garsington Road, Oxford OX4 2DQ, UK and 350 Main Street, Malden, MA 02148, USA.