waashk/acm huggingface dataset:
efficient clipping of arbitrary polygons  clipping 2d polygons is one of the basic routines in computer graphics. in rendering complex 3d images it has to be done several thousand times. efficient algorithms are therefore very important. we present such an efficient algorithm for clipping arbitrary 2d-polygons. the algorithm can handle arbitrary closed polygons, specifically where the clip and subject polygons may self-intersect. the algoirthm is simple and faster that vatti's (1992) algorithm, which was designed for the general case as well. simple modifications allow determination of union and set-theoretic differences of two arbitrary polygons.  gunther greiner kai hormann
a modular approach to simulation of robotic systems  this paper presents the results of a simulation effort performed as part of the icam robotics program. the initial q-gert simulation model is briefly described, followed by the presentation of a modular approach to simulation of robotic systems. in this approach, predefined q-gert modules, described by simple block diagrams, are assembled to produce a complete model. the system design logic is discussed and the available modules are briefly described. examples are presented in block diagram format. the advantages and limitations of the approach are discussed.  d. j. medeiros r. p. sadowski d. w. starks b. s. smith
autonomous systems intelligence  the evolution of unmanned and manned spacecraft indicates that significant degrees of autonomous operation for onboard health, fault, or performance management are becoming important. in particular, technology and mission studies of a permanently manned, evolutionary space station have surfaced the need for new computer system concepts incorporating autonomy and perhaps artificial (machine) intelligence. an evolving autonomous system with mixed degrees of autonomy, interdependent autonomous functions, and perhaps disparate artificial intelligences will require orchestration of the behavior of the entire system. an advanced concept of decision control, involving an explicit sequence of goal-directed decisions, is proposed as an executive machine-intelligent process by which the multiple, specialized "smart programs" or "machine intelligences" of an autonomous system could be controlled.  john l. anderson
surfaces from contours  this paper is concerned with the problem of reconstructing the surfaces of three-dimensional objects, given a collection of planar contours representing cross-sections through the objects. this problem has important aplications in biomedical research and instruction, solid modeling, and industrial inspection.  the method we describe produces a triangulated mesh from the data points of the contours which is then used in conjunction with a piecewise parametric surface-fitting algorithm to produce a reconstructed surface.  the problem can be broken into four subproblems: the correspondence problem (which contours should be connected by the surface?), the tiling problem (how should the contours be connected?), the branching problem (what do we do when there are branches in the surface?), and the surface- fitting problem (what is the precise geometry of the reconstructed surface?) we describe our system for surface reconstruction from sets of contours with respect to each of these subproblems. special attention is given to the correspondence and branching problems. we present a method that can handle sets of contours in which adjacent contours share a very contorted boundary, and we describe a new approach to solving the correspondence problem using a minimum spanning tree generated from the contours.  david meyers shelley skinner kenneth sloan
texture-based visibility for efficient lighting simulation  lighting simulations using hierarchical radiosity with clustering can be very slow when the computation of fine and artifact-free shadows is needed. to avoid the high cost of mesh refinement associated with fast variations of visibility across receivers, we propose a new hierarchical algorithm in which partial visibility maps can be computed on the fly, using a convolution technique for emitter- receiver configurations where complex shadows are produced. other configurations still rely on mesh subdivision to reach the desired accuracy in modeling energy transfer. in our system, therefore, radiosity is represented as a combination of textures and piecewise-constant or linear contributions over mesh elements at multiple hierarchical levels. we give a detailed description of the gather, push/pull, and display stages of the hierarchical radiosity algorithm, adapted to seamlessly integrate both representations. a new refinement algorithm is proposed, which chooses the most appropriate technique to compute the energy transfer and resulting radiosity distribution for each receiver/transmitter configuration. comprehensive error control is achieved by subdividing either the source or receiver in a traditional manner, or by using a blocker subdivision scheme that improves the quality of shadow masks without increasing the complexity of the mesh. results show that high-quality images are obtained in a matter of seconds for scenes with tens of thousands of polygons.  cyril soler f. x. sillion
sample-efficient strategies for learning in the presence of noise  in this paper, we prove various results about pac learning in the presence of malicious noise. our main interest is the sample size behavior of learning algorithms. we prove the first nontrivial sample complexity lower bound in this model by showing that order of ε/Δ2 \\+ d/Δ (up to logarithmic factors) examples are necessary for pac learning any target class of {0,1}-valued functions of vc dimension d, where ε is the desired accuracy and = ε/(1 + ε) - Δ the malicious noise rate (it is well known that any nontrivial target class cannot be pac learned with accuracy ε and malicious noise rate ≥ ε/(1 + ε), this irrespective to sample complexity). we also show that this result cannot be significantly improved in general by presenting efficient learning algorithms for the class of all subsets of d elements and the class of unions of at most d intervals on the real line. this is especialy interesting as we can also show that the popular minimum disagreement strategy needs samples of size d ε/Δ2, hence is not optimal with respect to sample size. we then discuss the use of randomized hypotheses. for these the bound ε/(1 + ε) on the noise rate is no longer true and is replaced by 2ε/(1 + 2ε). in fact, we present a generic algorithm using randomized hypotheses that can tolerate noise rates slightly larger than ε/(1 + ε) while using samples of size d/ε as in the noise-free case. again one observes a quadratic powerlaw (in this case d& ;#949;/Δ2, Δ = 2ε/(1 + 2ε) - ) as Δ goes to zero. we show upper and lower bounds of this order.  nicolò cesa-bianchi eli dichterman paul fischer eli shamir hans ulrich simon
the evaluation of legal knowledge based systems  evaluation strategies to assess the effectiveness of legal knowledge based systems enable strengths and limitations of systems to be accurately articulated. this facilitates efforts in the research community to develop systems and also promotes the adoption of research prototypes in the commercial world. however, evaluation strategies for systems that operate in a domain as complex as law are difficult to specify. in this paper, we present an evaluation framework put forward by reich and describe how this motivated the evaluation of our systems in australian family law. strategies surveyed include a comparison of linear regression with neural networks, user acceptance surveys, a comparison of system predictions with those from past cases, and a comparison of system outputs with those proposed by a panel of lawyers. specific criteria for the evaluation of explanation facilities are also described.  andrew stranieri john zeleznikow
synthesizing bidirectional texture functions for real-world surfaces  in this paper, we present a novel approach to synthetically generating bidirectional texture functions (btfs) of real-world surfaces. unlike a conventional two-dimensional texture, a btf is a six-dimensional function that describes the appearance of texture as a function of illumination and viewing directions. the btf captures the appearance change caused by visible small- scale geometric details on surfaces. from a sparse set of images under different viewing/lighting settings, our approach generates btfs in three steps. first, it recovers approximate 3d geometry of surface details using a shape-from-shading method. then, it generates a novel version of the geometric details that has the same statistical properties as the sample surface with a non-parametric sampling method. finally, it employs an appearance preserving procedure to synthesize novel images for the recovered or generated geometric details under various viewing/lighting settings, which then define a btf. our experimental results demonstrate the effectiveness of our approach.  xinguo liu yizhou yu heung-yeung shum
top ten blunders by visual designers literacy in a medium means being able to use it to communicate to our fellow human beings. literacy means that we can recognize good and bad attempts in the medium and avoid the latter while employing the former. by that standard, many, even in the graphics field, are not visually literate.as a consultant i'm called in to fix what's gone awry. i want to share with you some of the most frequently made --- and easily prevented --- blunders by visual designers, especially as they move to electronic media. william horton
detecting vortical phenomena in vector data by medium-scale correlation  the detection of vortical phenomena in vector data is one of the key issues in many technical applications, in particular in flow visualization. many existing approaches rely on purely local evaluation of the vector data. in order to overcome the limits of a local approach we choose to combine a local method with a correlation of a pre-defined generic vortex with the data in a medium-scale region. two different concepts of a generic vortices were tested on various sets of flow velocity vector data. the approach is not limited to the two generic patterns suggested here. the method was found to successfully detect vortices in cases were other methods fail.  h.-g. pagendarm b. henne m. rutten
light reflection functions for simulation of clouds and dusty surfaces  the study of the physical process of light interacting with matter is an important part of computer image synthesis since it forms the basis for calculations of intensities in the picture. the simpler models used in the past are being augmented by more complex models gleaned from the physics literature. this paper is another step in the direction of assimilating such knowledge. it concerns the statistical simulation of light passing through and being reflected by clouds of similar small particles. (it does not, however, address the cloud structure modeling problem). by extension it can be applied to surfaces completely covered by dust and is therefore a physical basis for various theories of diffuse reflection.  james f. blinn
displaced subdivision surfaces  in this paper we introduce a new surface representing, the displaced subdivision surface. it represents a detailed surface model as a scalar- valued displacement over a smooth domain surface. our representation defines both the domain surface and the displacement function using a unified subdivision framework, allowing for simple and efficient evaluation of analytic surface properties. we present a simple, automatic scheme for converting detailed geometric models into such a representation. the challenge in this conversion process is to find a simple subdivision surface that still faithfully expresses the detailed model as its offset. we demonstrate that displaced subdivision surfaces offer a number of benefits, including geometry compression, editing, animation, scalability, and adaptive rendering. in particular, the encoding of fine detail as a scalar function makes the representation extremely compact.  aaron lee henry moreton hugues hoppe
a comparative study of neural network algorithms applied to optical character recognition  three simple general purpose networks are tested for pattern classification on an optical character recognition problem. the feed-forward (multi-layer perceptron) network, the hopfield network and a competitive learning network are compared. the input patterns are obtained by optically scanning images of printed digits and uppercase letters. the resulting data is used as input for the networks with two-state input nodes; for others, features are extracted by template matching and pixel counting. the classification capabilities of the networks are compared with a nearest neighbour algorithm applied to the same feature vectors. the feed-forward network reaches the same recognition rates as the nearest neighbour algorithm, even when only a small percentage of the possible connections is used. the hopfield network performs less well, and overloading of the network remains a problem. recognition rates with the competitive learning network, if input patterns are clustered well, are again as high as the nearest neighbour algorithm.  p. patrick van der smagt
the relevance factor  search engines today are not always correct in their assessment of how well websites correlate with user-defined keywords. through extensive research, an adequate relevance factor formula was found and implemented. chris buckley, gerald salton, and james allan introduced this formula. it is an automated tool for website ranking, which corresponds more closely to how the users would rate the websites' significance. the formula depends partly on the number of times the user-defined keyword(s) appear(s) in the document.  kimberley deninger caroline cassigneul
model specification with respect to analysis  much potential exists for reducing the costs while also improving the quality of simulation models through the use of model development systems (mdss). we describe a specification language for discrete event models to be used in a mds.  our approach is to introduce an intermediate form between a conceptual model (the model as it exists in the mind of the modeler) and an implementation of that model in some programming language.  the model specification language described here is intended to be used in conjunction with a model specification generator (a program to assist a modeler or modeling team with the construction of model specifications).  a simple example is presented using this specification language. the example is used to illustrate some types of model analyses and documentation.  c. michael overstreet
keynote address-artificial intelligence and simulation  artificial intelligence is the latest buzzword and one of the hottest topics in the scientific community today. some experts are proclaiming that artificial intelligence (ai) has already emerged as one of the most significant technologies of this century. proponents are declaring that it will completely revolutionize management and the way we use computers. if these claims are even half true, then ai is bound to have a profound effect upon the art and science of simulation. the purpose of this paper is to provide a current overview of this rapidly evolving field, examine the potential of ai in simulation and the inevitability of it. we propose to explore the probable impact as well as forecast the directions it is likely to take.  robert e. shannon
silhouette clipping  approximating detailed with coarse, texture- mapped meshes results in polygonal silhouettes. to eliminate this artifact, we introduce silhouette clipping, a framework for efficiently clipping the rendering of coarse geometry to the exact silhouette of the original model. the coarse mesh is obtained using progressive hulls, a novel representation with the nesting property required for proper clipping. we describe an improved technique for constructing texture and normal maps over this coarse mesh. given a perspective view, silhouettes are efficiently extracted from the original mesh using a precomputed search tree. within the tree, hierarchical culling is achieved using pairs of anchored cones. the extracted silhouette edges are used to set the hardware stencil buffer and alpha buffer, which in turn clip and antialias the rendered coarse geometry. results demonstrate that silhouette clipping can produce renderings of similar quality to high- resolution meshes in less rendering time.  pedro v. sander xianfeng gu steven j. gortler hugues hoppe john snyder
fast volume rendering using a shear-warp factorization of the viewing transformation  several existing volume rendering algorithms operate by factoring the viewing transformation into a 3d shear parallel to the data slices, a projection to form an intermediate but distorted image, and a 2d warp to form an undistorted final image. we extend this class of algorithms in three ways. first, we describe a new object-order rendering algorithm based on the factorization that is significantly faster than published algorithms with minimal loss of image quality. shear-warp factorizations have the property that rows of voxels in the volume are aligned with rows of pixels in the intermediate image. we use this fact to construct a scanline-based algorithm that traverses the volume and the intermediate image in synchrony, taking advantage of the spatial coherence present in both. we use spatial data structures based on run-length encoding for both the volume and the intermediate image. our implementation running on an sgi indigo workstation renders a 2563 voxel medical data set in one second. our second extension is a shear-warp factorization for perspective viewing transformations, and we show how our rendering algorithm can support this extension. third, we introduce a data structure for encoding spatial coherence in unclassified volumes (i.e. scalar fields with no precomputed opacity). when combined with our shear-warp rendering algorithm this data structure allows us to classify and render a 2563 voxel volume in three seconds. the method extends to support mixed volumes and geometry and is parallelizable.  philippe lacroute marc levoy
webtop: 3d interactive optics on the web  the optics project (top) is a 3d interactive computer graphics system that visualizes optical phenomena. the primary motivation for creating top was to develop a tool to help undergraduate students learn optics. webtop is a web- based version of the system that encompasses a physical simulation, an overview of the theory involved, a showcase of examples, and a set of suggested exercises. the actual simulation is implemented using vrml, java, and the external authoring interface, and runs under multiple hardware/os/browser configurations. this work is significant in that it represents, to our knowledge, the first complete 3d interactive optics system on the web.  kiril vidimce john t. foley david c. banks yong-tze chi taha mzoughi
handling visual media preparation for ohio state's computer center workshops  at the ohio state university, approximately 20 general-purpose workshops are provided each quarter to service the needs of our user community. we have found it useful to organize the teaching materials for these workshops by standardizing the overhead transparencies that are used by our instructors. we have found that as a direct benefit of this team approach, we can maintain consistent organization in teaching our workshops; our instructors are certain to cover the important aspects of each topic; they are better able to assess the time that will be required to cover each topic and they are less likely to be side-tracked from their subject matter. it has become much easier to prepare and rotate the teaching assignments among our instructors by this method, and the instructors find that they can prepare for a workshop on shorter notice (should an emergency arise) if they've taught this workshop in the past.  three years ago, while each instructor prepared his or her own temporary overhead transparencies on clear acetate sheets with water soluble pens, we began the process of learning to pool our ideas, determine what concepts were consistent and relevant---and prepare permanent, standardized sets of overhead transparencies for many of our workshops. we have developed a filing system for maintaining our overhead transparency sets, and make periodic modifications to these sets. our transparency supplies consist of such simple materials as transparency film, water-based and permanent transparency pens, chartpak and zip-a-tone---all the way to the more sophisticated kroy lettering machine, the electrostatic versatec plotter and the newest addition--- sas/graph.  as the computer literacy rate has risen among our user community, the need for more technical and specialized instruction has also risen. by standardizing our workshop teaching materials, we have been able to free up more of the instructors' time and allow them to apply their research efforts toward new areas of computer literacy, while keeping pace with the needs and special interests of our user community.  the paper that i propose will discuss the basic considerations that are necessary to produce clear, visible, and attractive overhead transparencies. basic topics will include: simple dos and don'ts of transparency making, examples of good and poor transparency style; suggestions for redesigning overhead transparencies for better comprehension and visibility, and current visual media preparation at the ohio state university.  gail peters
computer graphics in scandanavia nowadays, computer graphics is a commonly utilized tool deployed both in universities and industry. a short overview like this can't hope to cover all activities, but i've attempted to give some examples from the field in scandinavia.overviews of computer graphics activity in scandinavia have previously been published in _computer graphics,_ 30(2) may 1996 (research) and 30(3) august 1996 (education). in addition, the journal _computers and graphics_ had a special issue on computer graphics in scandinavia in 1995\. in this overview we won't duplicate the material from the previous overviews, but rather attempt to give some additional examples of computer graphics research work. alain chesnais jose encarnacao #2287
model development revisited  a brief chronology of simulation software helps to understand the current status, which finds simulation modeling in a transactional period. viewed in the context of the model life cycle, the needs for more effective and efficient simulation model development can be identified. some consensus is evident in the definition of tools, but the approaches to improvement are charted quite differently by researchers and practitioners in the simulation community. at this juncture no clear directions have been established. however, the indications of convergence in the software and model development paradigms can only be beneficial for both communities.  richard e. nanoe
collapsing flow topology using area metrics  visualization of topological information of a vector field can provide useful information on the structure of the field. however, in turbulent flows standard critical point visualization will result in a cluttered image which is difficult to interpret. this paper presents a technique for collapsing topologics. the governing idea is to classify the importance of the critical points in the topology. by only displaying the more important critical points, a simplified depiction of the topology can be provided. flow consistency is maintained when collapsing the topology, resulting in a visualization which is consistent with the original topology. we apply the collapsing topology technique to a turbulent flow field.  wim de leeuw robert van liere