A number of sound synthesis methods rely on computing samples of a waveform from a mathematical description of the continuous signal. Such methods would include, for example, waveshaping, frequency modulation (FM), an...
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A number of sound synthesis methods rely on computing samples of a waveform from a mathematical description of the continuous signal. Such methods would include, for example, waveshaping, frequency modulation (FM), and wavetable synthesis. All of these techniques presently suffer from aliasing defects if the continuous waveform being sampled has significant energy above half the Nyqnist rate. However, this defect is not inherent in the description of the signal, but only in the nature of the regular sampling process. In this paper, stochastic sampling techniques, in particular Poisson and jittered sampling, are developed 'and analyzed in the time and frequency domains. Such techniques have already been used to generate alias-free power spectrum estimates [14] and to antialias computergraphics images [10, 11]. In sound synthesis, it is shown that these techniques allow the construction of alias-free approximations to signals at any sampling rate, regardless of the bandwidth or frequency content of the continuous signal. Stochastic sampling scatters high frequency components into broadband noise rather than folding them down into the audio range as in regular sampling. Broadband noise is more benign than narrowband aliases with similar energy. The probabilistic structure of the random sampling process controls the general spectral shape of the added noise. The spectrum of the noise for the sampling techniques mentioned above is described explicitly. Also, an explicit relationship is developed between the total signal to noise ratio and various parameters of the process, such as the the average sampling rate and the bandwidth of the continuous signal being sampled. Since the nature of the noise is known, noise reduction techniques can be used to increase the efficacy of a given average sampling rate. The stochastic sampling technique can be applied adaptively so that a greater number of samples are taken where the function varies most. An error estimate is used to det
Stochastic sampling techniques, in particular Poisson and fittered sampling, are developed and analyzed. These approaches allow the construction of alias-free approximations to continuous functions using discrete calc...
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ISBN:
(纸本)9780897911665
Stochastic sampling techniques, in particular Poisson and fittered sampling, are developed and analyzed. These approaches allow the construction of alias-free approximations to continuous functions using discrete calculations. Stochastic sampling scatters high frequency information into broadband noise rather than generating the false patterne produced by regular sampling. The type of randomness used in the sampling process controls the spectral character of the noise. The average sampling rate and the function being sampled determine the amount of noise that is produced. Stochastic sampling is applied adaptively so that a greater number of samples are taken where the function varies most. An estimate is used to determine how many samples to take over a given region. Noise reducing filters are used to increase the efficacy of a given sampling rate. The filter width is adaptively controlled to further improve performance. Stochastic sampling can be applied spatiotemporally as well as to other aspects of scene simulation. Ray tracing is one example of an image synthesis approach that can be antialiased by stochastic sampling.
An algorithm for computing ray traced pictures is presented, which adaptively subdivides scenes into S subregions, each with roughly uniform load. It can yield speedups of O(S2/3) over the standard *** algorithm can b...
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ISBN:
(纸本)9780897911382
An algorithm for computing ray traced pictures is presented, which adaptively subdivides scenes into S subregions, each with roughly uniform load. It can yield speedups of O(S2/3) over the standard *** algorithm can be mapped onto a parallel architecture consisting of a three dimensional array of computers which operate autonomously. The algorithm and architecture are well matched, so that communication overhead is small with respect to the computation, for sufficiently complex scenes. This allows close to linear improvements in performance, even with thousands of computers, in addition to the improvement due to *** algorithm and architecture provide mechanisms to gracefully degrade in response to excessive load. The architecture also tolerates failures of computers without errors in the computation.
Soft filling algorithms change the color of an anti-aliased region, maintaining the anti-aliasing of the region. The two published algorithms for soft filling work only if the foreground region is anti-aliased against...
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ISBN:
(纸本)9780897911382
Soft filling algorithms change the color of an anti-aliased region, maintaining the anti-aliasing of the region. The two published algorithms for soft filling work only if the foreground region is anti-aliased against a black background. This paper presents three new algorithms. The first fills against a region consisting of any two distinct colors, and is faster than the published algorithms on a pixel-by-pixel basis for an RGB frame buffer; the second fills against a region composed of three distinct colors; and the third fills against a region composed of four distinct colors. As the power of the algorithms increases, so do the number of assumptions they make, and the computational cost.
The Beta-spline introduced recently by Barsky is a generalization of the uniform cubic B-spline: parametric discontinuities are introduced in such a way as to preserve continuity of the unit tangent and curvature vect...
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The Beta-spline introduced recently by Barsky is a generalization of the uniform cubic B-spline: parametric discontinuities are introduced in such a way as to preserve continuity of the unit tangent and curvature vect...
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An interactive computergraphics package has been developed for computer aided design of linear multivariable control systems. The package employs an effective human/computer interface achieved through the use of menu...
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An interactive computergraphics package has been developed for computer aided design of linear multivariable control systems. The package employs an effective human/computer interface achieved through the use of menus orchestrated in an hierarchial tree structure. Numerous state-of-the art design algorithms and analysis methods are incorporated which communicate through the interactive and asynchronous function control interfaces of computergraphics system, creating an environment attractive to both industrial users and academics.
***, a mature, UNIX (FOOTNOTE: UNIX is a trademark of Bell Laboratories)-based computer-aided design tool is described. Its structure, performance, and limitations are discussed together with its applications to the d...
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ISBN:
(纸本)9780818600265
***, a mature, UNIX (FOOTNOTE: UNIX is a trademark of Bell Laboratories)-based computer-aided design tool is described. Its structure, performance, and limitations are discussed together with its applications to the design of multiple processor hardware/software systems and VLSI.
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