David Kurlander

A history-based macro by example system

Many tasks performed using computer interfaces are very repetitive. While programmers can write macros or procedures to automate these repetitive tasks, this requires special skills. Demonstrational systems make macro building accessible to all users, but most provide either no visual representation of the macro or only a textual representation. We have developed a history-based visual representation of commands in a graphical user interface. This representation supports the definition of macros by example in several novel ways. At any time, a user can open a history window, review the commands executed in a session, select operations to encapsulate into a macro, and choose objects and their attributes as arguments. The system has facilities to generalize the macro automatically, save it for future use, and edit it.

Graphical search and replace

Graphical search is a technique for finding all instances of a graphical pattern in a synthetic picture in which objects are regions bounded by lines and curves. The pattern may descirbe shape, color and other properties. Matched objects may be allowed to differ from the pattern in rotation and scale or may differ in shape by a specified tolerance. Graphical replace is a technique for replacing the shape, color, or other properties of matched objects with new properties described in a replacement pattern. Combined, the two techniques are similar to textual search and replace in text editors. Graphical search and replace can be used to make global changes to illustrations with repetitive patterns, independent of the means used to make those patterns. It can also be used to create a class of iterative or recursive shapes that can be specified by replacement rules.

Ray tracing with polarization parameters

Incorporating polarization parameters into the lighting model can enhance the physical realism of images rendered with a ray tracer. Polarization effects can be important in certain scenes, and the difference in rendering even simple scenes with and without proper treatment of polarization can be striking. All light waves possess a state of polarization, which changes almost every time light reflects off a material surface. A single reflection partially polarizes and may even completely polarize previously unpolarized light. Polarization influences the rendering of a scene because the reflected radiant intensity depends largely on the incident light wavess polarization state. E. Wolfs (1959) coherence matrix formalism of polarization has been incorporated into the Torrance-Sparrow reflectance model. This combination allows elegant quantitative derivations of the altered polarization state of light upon reflection in a ray tracer. Comparisons of identical scenes rendered with a conventional ray tracer and the ray tracer presented incorporating a polarization model show that the present method renders specular interobject reflections more accurately with respect to reflected radiance and color.<<ETX>>

Graphical editing by example (abstract)

INTRODUCTION Graphical editing, like many applications facilitated by computers, often involves repetitive tasks. To reduce repetition, programmers can write procedures to automate these tasks, however most users do not know how to program, and the repetitive tasks that they perform are frequently too specialized for the application programmer to anticipate. End users would benefit from the ability to customize and extend their applications for the tasks they usually perform.

Editable graphical histories: the video

INTRODUCTION Command histories are an important component of good user interfaces [3]. They allow users to review sequences of previously executed commands, and can provide an interface to an undo facility. Furthermore, they can support either a simple redo mechanism, or a more sophisticated macro-by-demonstration capability. Providing a visual representation of command histories in a graphical user interface presents a number of difficulties. Editable graphical histories [1, 2], a history representation that we have developed based on a comic-strip metaphor, overcomes many of these. Here we describe editable graphical histories, and in the accompanying videotape we demonstrate our test-bed implementation in the graphical editing mode of Chimera, a multi-modal editor.