Ronald N. Perry

Adaptively sampled distance fields: a general representation of shape for computer graphics

Adaptively Sampled Distance Fields (ADFs) are a unifying representation of shape that integrate numerous concepts in computer graphics including the representation of geometry and volume data and a broad range of processing operations such as rendering, sculpting, level-of-detail management, surface offsetting, collision detection, and color gamut correction. Its structure is uncomplicated and direct, but is especially effective for quality reconstruction of complex shapes, e.g., artistic and organic forms, precision parts, volumes, high order functions, and fractals. We characterize one implementation of ADFs, illustrating its utility on two diverse applications: 1) artistic carving of fine detail, and 2) representing and rendering volume data and volumetric effects. Other applications are briefly presented.

Antialiasing with Line Samples

A method, using a filter function, generates an anti-aliased discrete image from a continuous image including an edge. The method defines a line sample. A progressive convolution is derived from the filter function and the line sample. A pixel at a predetermined location in the discrete image is selected, and the line sample is oriented with respect to the selected pixel. A distance is measured from a point in the continuous image corresponding to the selected pixel to the edge along the oriented the line sample. The progressive convolution is evaluated at the measured distance to produce a weighted coverage value, and the weighted coverage value is associated with the pixel to anti-alias the pixel in the discrete image.

Designing with distance fields

Creating 3D computer models is a difficult, time consuming task. Existing systems capable of providing detailed, expressive models of sufficient quality for Hollywood or CAD can be labor intensive and complex, thus limiting creativity and the availability of good 3D models. During the past few years, several systems have been presented that address some of these limitations by using distance fields to represent and create models. The author presents the latest advancements to the Kizamu system and several new design paradigms that can make use of distance fields for creating and editing 3D geometry.

An improved representation for stroke-based fonts

Because a typical Asian typeface can consist of more than 12,000 glyphs, traditional scalable outline-based fonts require 5-10 MBs of memory. This requirement is particularly problematic in mobile devices (e.g. cell phones and PDAs) and embedded systems (e.g. car navigation systems)where memory is at a premium. Existing commercial solutions (e.g. by Bitstream and Monotype Imaging) represent glyphs using simplified uniform-width strokes. However, these light-weigh ( 250 KBs) stroke-based fonts lack the detail, expressiveness, and variety needed for optimal legibility and true cultural acceptance (Figure 1). Although METAFONT [Knuth 1986] is stroke-based and provides sufficient detail and expressiveness, it requires the type designer to be proficient in mathematics, rasterization and programming.