An artificial chemistry with composition devices borrowed from object-oriented and functional programming languages was introduced in prior work. Actors in object-oriented combinator chemistry are embedded in space and subject to diffusion; since they are neither created nor destroyed, mass is conserved. This paper further develops these ideas and applies them in significant ways. First, it introduces the concept of a self-replicating systems normalized complexity. Normalized complexity permits comparisons between artificial organisms defined in different virtual worlds by explicitly accounting for the relative complexities of both organism and world. Second, object-oriented combinator chemistry is used to define a parallel, asynchronous, spatially distributed self-replicating system modeled in part on the living cell. This system is strongly constructive since interactions among its parts results in the construction of more of these same parts; constructed parts are assembled from elements of a few primitive types. The systems high normalized complexity is contrasted with that of a simple composome, which is also defined.

Joint Polar Satellite System (JPSS) data product improvement requires a substantial record of on-orbit data extending over years. Such a data record now exists for the JPSS instruments developed for the Suomi National Polar Orbiting Partnership (SNPP) risk reduction mission. SNPP has now provided well over three years of on-orbit data from four JPSS instruments and derived data products. It is now feasible to apply a system engineering approach to data product improvement. In this approach on-orbit performance characteristics are traced back to instrument and algorithm design characteristics and pre-launch test data. During the instrument development phase system engineering was applied in the reverse direction, to trade off and optimize designs to meet requirements based on predicted performance. The key to data product improvement is comparison of on-orbit performance with performance predicted pre-launch and feedback of comparison findings into the design and development process for future JPSS instruments and algorithms.

Recent work showed how an expression in a functional programming language can be compiled into a massively redundant asynchronous spatial computation called a distributed virtual machine. A DVM is comprised of bytecodes reified as actors undergoing diffusion and communicating via messages containing encapsulated virtual machine states. Significantly, it was shown that both the efficiency and the robustness of expression evaluation by DVM increase with redundancy. In the present work, spatial computations that become more efficient and robust over time are described. They accomplish this by self-replication, which increases the redundancy of the elements of which they are comprised. The first and simplest of these self-replicating DVMs copies itself by reflection; it reads itself from a contiguous range of memory. The remainder are quines. As such, they reproduce by translating and transcribing self-descriptions. The nature of the self-descriptions and of the translation and transcription processes differ in each case. The most complex selfreplicating DVM described represents a fundamentally new kind of artificial organism–a machine language program reified as a spatial computation that reproduces by compiling its own source-code.

Although it is in general difficult to track articulated hand motion, exemplar-based approaches provide a robust solution for hand gesture recognition. Presumably, a rich set of dynamic hand gestures are needed for a meaningful recognition system. How to build the visual representation for the motion patterns is the key for scalable recognition. We propose a novel representation based on the divergence map of the gestural motion field, which transforms motion patterns into spatial patterns. Given the motion divergence maps, we leverage modern image feature detectors to extract salient spatial patterns, such as Maximum Stable Extremal Regions (MSER). A local descriptor is extracted from each region to capture the local motion pattern. The descriptors from gesture exemplars are subsequently indexed using a pre-trained vocabulary tree. New gestures are then matched efficiently with the database gestures with a TF-IDF scheme. Our extensive experiments on a large hand gesture database with 10 categories and 1050 video samples validate the efficacy of the extracted motion patterns for gesture recognition. The proposed approach achieves an overall recognition rate of 97.62%, while the average recognition time is only 34.53 ms.

Despite decades of study, robust shadow detection remains difficult, especially within a single color image. We describe a new approach to detect shadow boundaries in images of outdoor scenes lit only by the sun and sky. The method first extracts visual features of candidate edges that are motivated by physical models of illumination and occluders. We feed these features into a Support Vector Machine (SVM) that was trained to discriminate between most-likely shadow-edge candidates and less-likely ones. Finally, we connect edges to help reject non-shadow edge candidates, and to encourage closed, connected shadow boundaries. On benchmark shadow-edge data sets from Lalonde et al. and Zhu et al., our method showed substantial improvements when compared to other recent shadow-detection methods based on statistical learning.

We present a semi-automatic method for creating shadow mattes in cel animation. In conventional cel animation, shadows are drawn by hand, in order to provide visual cues about the spatial relationships and forms of characters in the scene. Our system creates shadow mattes based on hand-drawn characters, given high-level guidance from the user about depths of various objects. The method employs a scheme for "inflating" a 3D figure based on hand-drawn art. It provides simple tools for adjusting object depths, coupled with an intuitive interface by which the user specifies object shapes and relative positions in a scene. Our system obviates the tedium of drawing shadow mattes by hand, and provides control over complex shadows falling over interesting shapes. Keywords: Shadows, cel animation, inflation, sketching, NPR. URL: http://www.cs.princeton.edu/gfx/proj/cel shadows 1 Introduction Shadows provide important visual cues for depth, shape, contact, movement, and lighting in our perce...

Techniques from the image and signal processing domain can be successfully applied to designing, modifying, and adapting animated motion. For this purpose, we introduce multiresolution motion filtering, multitarget motion interpolation with dynamic timewarping, waveshaping and motion displacement mapping. The techniques are well-suited for reuse and adaptation of existing motion data such as joint angles, joint coordinates or higher level motion parameters of articulated figures with many degrees of freedom. Existing motions can be modified and combined interactively and at a higher level of abstraction than conventional systems support. This general approach is thus complementary to keyframing, motion capture, and procedural animation.

The work described here extends the power of 2D animation with a form of texture mapping conveniently controlled by line drawings. By tracing points, line segments, spline curves, or filled regions on an image, the animator defines features which can be used to animate the image. Animations of the control features deform the image smoothly. This development is in the tradition of “skeleton”-based animation, and “feature”-based image metamorphosis. By employing numerics developed in the computer vision community for rapid visual surface estimation, several important advantages are realized. Skeletons are generalized to include curved “bones,” the interpolating surface is better behaved, the expense of computing the animation is decoupled from the number of features in the drawing, and arbitrary holes or cuts in the interpolated surface can be accommodated. The same general scattered data interpolation technique is applied to the problem of mapping animation from one image and set of features to another, generalizing the prescriptive power of animated sequences and encouraging reuse of animated motion.

Image-space simplifications have been used to accelerate the calculation of computer graphic images since the dawn of visual simulation.Texture mapping has been used to provide a means by which images may themselves be used as display primitives.The work reported by this paper endeavors to carry this concept to its logical extreme by using interpolated images to portray three-dimensional scenes.The special-effects technique of morphing, which combines interpolation of texture maps and their shape, is applied to computing arbitrary intermediate frames from an array of prestored images.If the images are a structured set of views of a 3D object or scene, intermediate frames derived by morphing can be used to approximate intermediate 3D transformations of the object or scene.Using the view interpolation approach to synthesize 3D scenes has two main advantages.First, the 3D representation of the scene may be replaced with images.Second, the image synthesis time is independent of the scene complexity.The correspondence between images, required for the morphing method, can be predetermined automatically using the range data associated with the images.The method is further accelerated by a quadtree decomposition and a view-independent visible priority.Our experiments have shown that the morphing can be performed at interactive rates on today's high-end personal computers.Potential applications of the method include virtual holograms, a walkthrough in a virtual environment, image-based primitives and incremental rendering.The method also can be used to greatly accelerate the computation of motion blur and soft shadows cast by area light sources.

This paper advances a means by which the conventions and methods of digital "painting" and image manipulation programs can be extended into the third dimension, providing sculpting tools that are natural and appropriate for a restricted but very useful class of models. Attempts to approximate "drawing" in 3D do not necessarily involve computer graphics [Gregory71]. Efforts in this area are a subject of continuing graphics research [Schmandt82], [Sachs89]. The key to the approach undertaken in the work described here is the use of an unusual hardware technique for displaying video rasters as surfaces. With such a display, existing software for 2D graphics and image processing can be used, without modification, for creating and modifying three-dimensional surfaces. The resulting raster data can then be converted into conventional 3D databases for further processing and display. The aim of this research is to create consistent, unified methods for computer-assisted drawing, painting, modeling, and animation.

As computer graphics technique rises to the challenge of rendering lifelike performers, more lifelike performance is required. The techniques used to animate robots, arthropods, and suits of armor, have been extended to flexible surfaces of fur and flesh. Physical models of muscle and skin have been devised. But more complex databases and sophisticated physical modeling do not directly address the performance problem. The gestures and expressions of a human actor are not the solution to a dynamic system. This paper describes a means of acquiring the expressions of real faces, and applying them to computer-generated faces. Such an "electronic mask" offers a means for the traditional talents of actors to be flexibly incorporated in digital animations. Efforts in a similar spirit have resulted in servo-controlled "animatrons," high-technology puppets, and CG puppetry [1]. The manner in which the skills of actors and puppetteers as well as animators are accommodated in such systems may point the way for a more general incorporation of human nuance into our emerging computer media.The ensuing description is divided into two major subjects: the construction of a highly-resoved human head model with photographic texture mapping, and the concept demonstration of a system to animate this model by tracking and applying the expressions of a human performer.

The mapping of images onto surfaces may substantially increase the realism and information content of computer-generated imagery. The projection of a flat source image onto a curved surface may involve sampling difficulties, however, which are compounded as the view of the surface changes. As the projected scale of the surface increases, interpolation between the original samples of the source image is necessary; as the scale is reduced, approximation of multiple samples in the source is required. Thus a constantly changing sampling window of view-dependent shape must traverse the source image.

Shadowing has historically been used to increase the intelligibility of scenes in electron microscopy and aerial survey. Various methods have been published for the determination of shadows in computer synthesized scenes. The display of shadows may make the shape and relative position of objects in such scenes more comprehensible; it is a technique lending vividness and realism to computer animation.To date, algorithms for the determination of shadows have been restricted to scenes constructed of planar polygons. A simple algorithm is described which utilizes Z-buffer visible surface computation to display shadows cast by objects modelled of smooth surface patches. The method can be applied to all environments, in fact, for which visible surfaces can be computed. The cost of determining the shadows associated with each light source is roughly twice the cost of rendering the scene without shadows, plus a fixed transformation overhead which depends on the image resolution. No extra entities are added to the scene description in the shadowing process. This comprehensive algorithm, which permits curved shadows to be cast on curved surfaces, is contrasted with a less costly method for casting the shadows of the environment on a single ground plane.In order to attain good results, the discrete nature of the visible-surface computations must be treated with care. The effects of dither, interpolation, and geometric quantization at different stages of the shadowing algorithm are examined. The special problems posed by self-shadowing surfaces are described.