Stochastic Sampling in Computer Graphics Pixar（随机抽样在计算机图形学中皮克斯）.pdfVIP

Stochastic Sampling in Computer Graphics ROBERT L. COOK Pixar Ray tracing, ray casting, and other forms of point sampling are important techniques in computer graphics, but their usefulness has been undermined by aliasing artifacts. In this paper it is shown that these artifacts are not an inherent part of point sampling, but a consequence of using regularly spaced samples. If the samples occur at appropriate nonuniformly spaced locations, frequencies above the Nyquist limit do not alias, but instead appear as noise of the correct average intensity. This noise is much less objectionable to our visual system than aliasing. In ray tracing, the rays can be stochastically distributed to perform a Monte Carlo evaluation of integrals in the rendering equation. This is called distributed ray tracing and can be used to simulate motion blur, depth of field, penumbrae, gloss, and translucency. Categories and Subject Descriptors: 1.3.3 [Computer Graphics]: Picture/Image Generation; 1.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism General Terms: Algorithms Additional Key Words and Phrases: Antialiasing, filtering, image synthesis, Monte Carlo integration, motion blur, raster graphics, ray tracing, sampling, stochastic sampling 1. INTRODUCTION Because pixels are discrete, computer graphics is inherently a sampling process. The pixel size determines an upper limit to the frequencies that can be displayed. This limit, one cycle every two pixels, is called the Nyquist limit. An attempt to disp