MntractA solution to the hidden rmrface elimination problem called Beam W&g is described. B&n tracing ia related to ray tracing but usea spatial coherence within the scene, and area coherence within the image to batch computationa. Beam tracing is an object space solution to the hidden surface problem.Beam tracing is formulated in terms of its principal subprocesses: intersection, sorting, and clipping. A Hierarchicd Scene Representation ia proposed. This incorporates the space decomposition idea of the BSP tree [h&s, Kedem and Naylor, SO] dong with the convex polytope intersection detection technique of [Dobkii snd Kirkpatrick, 831 to interleave and efficiently solve the intelsection and sorting subproblems of beam tracing.

The design of Godot, a computer system for computer-aided room acoustics modeling and simulation, was described in an earlier paper [J. Acoust. Soc. Am. Suppl. 1 69, S36 (1981)]. In this paper, issues affecting its use in the production environment are discussed and current research issues are examined briefly. The system has been moved from a mainframe computer to a minicomputer having graphics facilities suitable for interactive design; we will review the way room acoustics modeling and simulation are treated in the larger context of computer-aided architectural design. Taped examples of simple simulations will be presented, and compared with examples recorded in the actual rooms. Godot currently traces sound beams incrementally; in this way it avoids exhaustive intersection testing with all faces in the room representation. Current work aims at generalizing the orientation-dependent “bounding boxes” used in coarse “hit” detection to yield an intrinsic bounding volume for each wall element. As a side benefit this method will allow us to model moving portions of a room. [Work supported by the Science Council of British Columbia, grant ♯41 (RC-4).]

No abstract

Godot is a software system for computer-aided room acoustics design and simulation. It is able to generate an audible simulation of arbitrarily directional sound sources in arbitrarily shaped rooms, incorporating diffraction effects. This paper reviews the design of the system. A polyhedral representation is used to model the room under consideration. Sound beams, defined by their axis directions and directivity factors, are traced as they traverse the room, and their “hits” upon a receiver position are noted. A perspective projection from the image of the source onto a “window” perpendicular to the beam axis is used to determine which edges of the room fall within a beam and hence can generate diffracted waves. The power transfer function of each path from source to receiver is used to derive the autocorrelation coefficients associated with the path, and linear least-squares prediction is used to determine the coefficients of an autoregressive digital filter which will match the frequency response of the path. When driven by arbitrary digitized program material, the parallel channels of the system, representing the paths to the receiver, will give an audible simulation of the conditions being considered.