waashk/acm huggingface dataset:
inverse kinematics positioning using nonlinear programming for highly articulated figures  an articulated figure is often modeled as a set of rigid segments connected with joints. its configuration can be altered by varying the joint angles. although it is straight forward to compute figure configurations given joint angles (forward kinematics), it is more difficult to find the joint angles for a desired configuration (inverse kinematics). since the inverse kinematics problem is of special importance to an animator wishing to set a figure to a posture satisfying a set of positioning constraints, researchers have proposed several different approaches. however, when we try to follow these approaches in an interactive animation system where the object on which to operate is as highly articulated as a realistic human figure, they fail in either generality or performance. so, we approach this problem through nonlinear programming techniques. it has been successfully used since 1988 in the spatial constraint system within jack, a human figure simulation system developed at the university of pennsylvania, and proves to be satisfactorily efficient, controllable, and robust. a spatial constraint in our system involves two parts: one constraint on the figure, the end- effector, and one on the spatial environment, the goal. these two parts are dealt with separately, so that we can achieve a neat modular implementation. constraints can be added one at a time with appropriate weights designating the importance of this constraint relative to the others and are always solved as a group. if physical limits prevent satisfaction of all the constraints, the system stops with the (possibly local) optimal solution for the given weights. also, the rigidity of each joint angle can be controlled, which is useful for redundant degrees of freedom.  jianmin zhao norman i. badler
parallel processing image synthesis and anti-aliasing  the continuing evolution of microelectronics provides the tools for developing new methods of synthesizing digital images by utilizing parallel processing architectures which hold the promise of reliability, flexibility and low cost. beginning with the earliest real-time flight simulators, parallel processing architectures for image synthesis have been built, but "anti-aliasing" remains a problem. a parallel processing architecture is described and simulated which consists of a serial chain of processors which produces as output a depth sorted list of those objects which are at least potentially visible at each pixel. the lists are then filtered to provide the final shading at each pixel.  richard weinberg
the design of a multi-microprocessor based simulation computer - ii  this paper presents further results in development of a discrete event simulation computer based on a network of micro processors. the network is being designed by identifying simulation tasks which may be performed in parallel with other computation required by the simulation, and then assigning those subtasks to attached processing elements in the network. the tasks of priority queue processing and state accounting are considered in this paper. a three attached processor simulation computer has been designed, using two processors for the event set and the third for state statistics accumulation. in a simulation model of this system, a forty to fifty percent reduction in the execution of a benchmark simulation program is easily achieved. (the benchmark program itself uses an adaptive scheduling algorithm). further observations and suggestions for future research are presented.  john craig comfort
time-critical multiresolution scene rendering  we describe a framework for time-critical rendering of graphics scenes composed of a large number of objects having complex geometric descriptions. our technique relies upon a scene description in which objects are represented as multiresolution meshes. we perform a constrained optimization at each frame to choose the resolution of each potentially visible object that generates the best quality image while meeting timing constraints. the technique provides smooth level-of-detail control and aims at guaranteeing a uniform, bounded frame rate even for widely changing viewing conditions. the optimization algorithm is independent from the particular data structure used to represent multiresolution meshes. the only requirements are the ability to represent a mesh with an arbitrary number of triangles and to traverse a mesh structure at an arbitrary resolution in a short predictable time. a data structure satisfying these criteria is described and experimental results are discussed.  enrico gobbetti eric bouvier
a linear time exact hidden surface algorithm  this paper presents a new hidden surface algorithm. its output is the set of the visible pieces of edges and faces, and is as accurate as the arithmetic precision of the computer. thus calculating the hidden surfaces for a higher resolution device takes no more time. if the faces are independently and identically distributed, then the execution time is linear in the number of faces. in particular, the execution time does not increase with the depth complexity.  this algorithm overlays a grid on the screen whose fineness depends on the number and size of the faces. edges and faces are sorted into grid cells. only objects in the same cell can intersect or hide each other. also, if a face completely covers a cell then nothing behind it in the cell is relevant.  three programs have tested this algorithm. the first verified the variable grid concept on 50,000 intersecting edges. the second verified the linear time, fast speed, and irrelevance of depth complexity for hidden lines on 10,000 spheres. this also tested depth complexities up to 30, and showed that perspective scenes with the farther objects smaller are even faster to calculate. the third verified this for hidden surfaces on 3000 squares.  wm randolph franklin
a fast relighting engine for interactive cinematic lighting design  we present new techniques for interactive cinematic lighting design of complex scenes that use procedural shaders. deep-framebuffers are used to store the geometric and optical information of the visible surfaces of an image. the geometric information is represented as collections of oriented points, and the optical information is represented as bi-directional reflection distribution functions, or brdfs. the brdfs are generated by procedurally defined surface texturing functions that spatially vary the surfaces' appearances.  the deep-framebuffer information is rendered using a multi-pass algorithm built on the opengl graphics pipeline. in order to handle both physically- correct as well as non-realistic reflection models used in the film industry, we factor the brdf into independent components that map onto both the lighting and texturing units of the graphics hardware. a similar factorization is used to control the lighting distribution. using these techniques, lighting calculations can be evaluated 2500 times faster than previous methods. this allows lighting changes to be rendered at rates of 20hz in static environments that contain millions of objects of with dozens of unique procedurally defined surface properties and scores of lights.  reid gershbein pat hanrahan
the analyst - a workstation for analysis and design  this paper describes a system currently being developed called the "analyst". the analyst is a support system for analysis and design methods. the method support facilities are being implemented using expert system or knowledge based techniques. the user can add rules for additional analysis of the application facts. the explicit representation of rules and facts (i.e. the knowledge base) makes it relatively easy to add methods to cover different phases or aspects of the software life cycle.  mark stephens ken whitehead
automatic indexing  one of the first projects in computer analysis of natural language was to devise procedures for representing the subject content of a document by a few text-derived terms, a process called automatic indexing. although many developments have taken place over the years, the essential techniques of automatic indexing continue to focus on answering three basic questions:  1\\. how can automatic indexing be made to more adequately represent the subject content of a document?  2\\. how can automatic indexing improve recall by increasing the number of relevant documents retrieved?  3\\. how can automatic indexing improve precision by decreasing the number of non-relevant documents retrieved?  during this tutorial session, we will review the advances that have been made, and the procedures that have been devised, to improve the effectiveness of automatic indexing. we will then consider the question of whether online retrieval systems can rely entirely on automatic indexing to achieve adequate retrieval effectiveness or whether some manual pre-indexing is still necessary.  harold borko
prolog as a simulation language  prolog is a rather new language and is very different from traditional languages. prolog is favored by the japanese for their fifth generation computer systems. the acronym prolog is derived from programming in logic and emphasizes the derivation of the language from predicate logic. prolog can be considered as a general purpose very high level language, best suited for general symbol manipulation, intelligent and flexible database handling or problems, where some kind of search is required. examples of application areas are computer aided design, database and "knowledge-base" management, natural language processing and rapid prototyping.  it is the purpose of this paper to demonstrate, how prolog can be used as a tool in a simulation project.  the paper consists of two parts: a survey of the language prolog and a description of t-prolog, a prolog based simulation language, using a process interaction approach.  heimo h. adelsberger
computer rendering of fractal curves and surfaces  fractals are a class of highly irregular shapes that have myriad counterparts in the real world, such as islands, river networks, turbulence, and snowflakes. classic fractals include brownian paths, cantor sets, and plane- filling curves. nearly all fractal sets are of fractional dimension and all are nowhere differentiable.  previously published procedures for calculating fractal curves employ shear displacement processes, modified markov processes, and inverse fourier transforms. they are either very expensive or very complex and do not easily generalize to surfaces. this paper presents a family of simple methods for generating and displaying a wide class of fractal curves and surfaces. in so doing, it introduces the concept of statistical subdivision in which a geometric entity is split into smaller entities while preserving certain statistical properties.  loren c. carpenter
the "parallel vectors" operator: a vector field visualization primitive  in this paper we propose an elementary operation on a pair of vector fields as a building block for defining and computing global line-type features of vector or scalar fields. while usual feature definitions often are procedural and therefore implicit, our operator allows precise mathematical definitions. it can serve as a basis for comparing feature definitions and for reuse of algorithms and implementations. applications focus on vortex core methods.  ronald peikert martin roth
towards a legal analogical reasoning system: knowledge representation and reasoning methods  analogy has many important functions in the domain of law. since the number of legal rules is restricted and their content is often incomplete, it is necessary at times for a lawyer to opt for an analogical application of a legal rule to a given case in order to decide the case properly. he may apply the rule, though it may not have originally been deemed related to such an event, on the basis of some similarity between the event of the case and the requirement of the relevant legal rule. this type of reasoning is called legal analogy. this paper analyzes an actual case of legal analogy in the field of japanese civil law in order to clarify the reasoning methods used in analogy, as well as knowledge to justify the analogy. finally it will be shown how the knowledge is utilized in a symbolic reasoning system both in terms of inverse and standard resolution.  hajime yoshino makoto haraguchi seiichiro sakurai sigeru kagayama
it knows what you're going to do: adding anticipation to a quakebot  the complexity of ai characters in computer games is continually improving; however they still fall short of human players. in this paper we describe an ai bot for the game quake ii that tries to incorporate some of the missing capabilities. this bot is distinguished by its ability to build its own map as it explores a level, use a wide variety of tactics based on its internal map, and in some cases, anticipate its opponents actions. the bot was developed in the soar architecture and uses dynamical hierarchical task decomposition to organize it knowledge and actions. it also uses internal prediction based on its own tactics to anticipate its opponents actions. this paper describes the implementation, its strengths and weaknesses, and discusses future research.  john e. laird
haptic rendering: programming touch interaction with virtual objects  haptic rendering is the process of computing and generating forces in response to user interactions with virtual objects. recent efforts by our team at mit's ai laboratory have resulted in the development of haptic interface devices and algorithms for generating the forces of interaction with virtual objects. this paper focuses on the software techniques needed to generate sensations of contact interaction and material properties. in particular, the techniques we describe are appropriate for use with the phantom haptic interface, a force generating display device developed in our laboratory. we also briefly describe a technique for representing and rendering the feel of arbitrary polyhedral shapes and address issues related to rendering the feel of non- homogeneous materials. a number of demonstrations of simple haptic tasks which combine our rendering techniques are also described.  k. salisbury d. brock t. massie n. swarup c. zilles
a repository of knowledge about handling exceptions in multi-agent systems  a critical challenge to creating effective agent- based systems is allowing them to operate effectively in environments where failures (' exceptions') can occur. an important barrier to achieving this has been the lack of systematized dissemination of exception handling techniques. this paper describes a semi- formal web- accessible repository, built as an augmentation of the mit process handbook, that is designed to enable learning about, adding to, and exploiting multiagent system exception handling expertise.  mark klein
an efficient representation for irradiance environment maps  we consider the rendering of diffuse objects under distant illumination, as specified by an environment map. using an analytic expression for the irradiance in terms of spherical harmonic coefficients of the lighting, we show that one needs to compute and use only 9 coefficients, corresponding to the lowest-frequency modes of the illumination, in order to achieve average errors of only 1%. in other words, the irradiance is insensitive to high frequencies in the lighting, and is well approximated using only 9 parameters. in fact, we show that the irradiance can be procedurally represented simply as a quadratic polynomial in the cartesian components of the surface normal, and give explicit formulae. these observations lead to a simple and efficient procedural rendering algorithm amenable to hardware implementation, a prefiltering method up to three orders of magnitude faster than previous techniques, and new representations for lighting design and image-based rendering.  ravi ramamoorthi pat hanrahan
map/1 tutorial  map/1tm is a simulation-based modeling and analysis program developed by pritsker and associates for use in designing and evaluating discrete part manufacturing systems. map/1 is a generalized model of a discrete part manufacturing system, which is parameterized to represent a specific manufacturing facility. parameters which describe the manufacturing facility configuration and associated operating rules are input to the map/1 analysis program, which produces a set of predefined output reports and provides measures of facility performance. using map/1, in-depth simulation analyses may be performed to investigate alternative system configurations and operating procedures.  robin j. miner laurie j. rolston
experimental investigation of a forest of quadtrees (abstract only)  forest of quadtrees have recently been recognized as an efficient data structure to store quadtrees. of special interest is the case in which a single 2m by 2m square region is contained in a 2n by 2n image. a study of the effect of placement of the square region inside the image was done to determine the usefulness of forest of quadtrees. the results indicate that a forest of quadtrees improves over the normal quadtree for many positions of the square region as the worst case occurs when both structures are equal. an analysis of the best and worst case position will be presented.  narinder lakhani s. s. iyengar
adaptation of scan and slit-scan techniques to computer animation  the adaptation and generalization of scan and slit-scan animation stand techniques for use in computer generated animation is discussed. scan and slit-scan techniques are based on moving artwork, camera, and, for slit-scan, a thin aperture while the camera shutter is open. these processes can be described as selectively sampling an environment over time and recording the result as a single image. sequences of such images form the animated film. rather than use mechanical means to accomplish this, it is possible to develop algorithms which mimic this processes but are based on sampling dynamic environment descriptions to generate computer produced images.  the use of computer graphics allows these techniques to be generalized in ways difficult or impossible even with very elaborate animation stands. use of multiple independent scanning apertures and three-dimensional environments are natural generalizations.  the exact algorithms used depend on the characteristics of the graphics systems used. an approach based on using a real-time shaded graphics system and an approach using frame buffer systems are outlined. the first approach can also be applied to refresh vector graphics systems.  frederic i. parke
timewarp rigid body simulation  the traditional high-level algorithms for rigid body simulation work well for moderate numbers of bodies but scale poorly to systems of hundreds or more moving, interacting bodies. the problem is unnecessary synchronization implicit in these methods. jefferson's timewarp algorithm [22] is a technique for alleviating this problem in parallel discrete event simulation. rigid body dynamics, though a continuous process, exhibits many aspects of a discrete one. with modification, the timewarp algorithm can be used in a uniprocessor rigid body simulator to give substantial performance improvements for simulations with large numbers of bodies. this paper describes the limitations of the traditional high-level simulation algorithms, introduces jefferson's algorithm, and extends and optimizes it for the rigid body case. it addresses issues particular to rigid body simulation, such as collision detection and contact group management, and describes how to incorporate these into the timewarp framework. quantitative experimental results indicate that the timewarp algorithm offers significant performance improvements over traditional high-level rigid body simulation algorithms, when applied to systems with hundreds of bodies. it also helps pave the way to parallel implementations, as the paper discusses.  brian mirtich
a framework for assisted exploration with collaboration  we approach the problem of exploring a virtual space by exploiting positional and camera- model constraints on navigation to provide extra assistance that focuses the user's explorational wanderings on the task objectives. our specific design incorporates not only task-based constraints on the viewer's location, gaze, and viewing parameters, but also a personal "guide" that serves two important functions: keeping the user oriented in the navigation space, and "pointing" to interesting subject areas as they are approached. the guide's cues may be ignored by continuing in motion, but if the user stops, the gaze shifts automatically toward whatever the guide was interested in. this design has the screndipitous feature that it automatically incorporates a nested collaborative paradigm simply by allowing any given viewer to be seen as the "guide" of one or more viewers following behind; the leading automated guide (we tend to select a guide dog for this avatar) can remind the leading live human guide of interesting sites to point out, while each real human collaborator down the chain has some choices about whether to follow the local leader's hints. we have chosen vrml as our initial development medium primarily because of its portability, and we have implemented a variety of natural modes for leading and collaborating, including ways for collaborators to attach to and detach from a particular leader.  eric a. wernert andrew j. hanson