visibility

	Fast and Accurate Geometric Sound Propagation using Visibility Computations Anish Chandak, Lakulish Antani, Micah Taylor, Dinesh Manocha International Symposium on Room Acoustics 2010 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. Paper
	Efficient Finite-Edge Diffraction using Conservative From-Region Visibility Lakulish Antani, Anish Chandak, Micah Taylor, Dinesh Manocha Applied Acoustics (Volume 73, Issue 3, March 2012) We present a fast algorithm to perform sound propagation in complex 3D scenes. Our approach computes propagation paths from each source to the listener by taking into account specular reflections and higher-order edge diffractions around finite edges in the scene. We use the well known Biot-Tolstoy-Medwin diffraction model along with efficient algorithms for region-based visibility to cull away primitives and significantly reduce the number of edge pairs that need to be processed. The performance of region-based visibility computation is improved by using a fast occluder selection algorithm that can combine small, connected triangles to form large occluders and perform conservative computations at objectspace precision. We show that our approach is able to reduce the number of visible primitives considered for sound propagation by a factor of 2 to 4 for second order edge diffraction as compared to prior propagation algorithms. We demonstrate and analyze its performance on multiple benchmarks. Paper Video Website
	FastV: From-Point Visibility Culling for Complex Models Anish Chandak, Lakulish Antani, Micah Taylor, Dinesh Manocha Eurographics Symposium on Rendering 2009 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. Paper Video Website