Presence has been studied in the context of virtual environments for nearly thirty years, but the field has yet to reach consensus on even basic issues of definition and measurement, and there are many open research questions. We gather many of these open research questions and systematically group them according to what we believe are five key constructs that inform user experience in virtual environments: immersion, coherence, Place Illusion, Plausibility Illusion, and presence. We also report on the design and results of a study that investigated the effects of immersion and coherence on user experience in a stressful virtual visual cliff environment. In this article, each participant experienced a given VE in one of four conditions chosen from a 2x2 design: high or low levels of immersion and high or low levels of coherence. We collected both questionnaire-based and physiological metrics. Several existing presence questionnaires could not reliably distinguish the effects of immersion from those of coherence. They did, however, indicate that high levels of both together result in higher presence, compared any of the other three conditions. This suggests that "breaks in PI" and "breaks in Psi" belong to a broader category of "breaks in experience," any of which result in a degraded user experience. Participants' heart rates responded markedly differently in the two coherence conditions; no such difference was observed across the immersion conditions. This indicates that a VE that exhibits unusual or confusing behavior can cause stress in a user that affects physiological responses, and that one must take care to eliminate such confusing behaviors if one is using physiological measurement as a proxy for subjective experience in a VE.

We report on the design and results of two experiments investigating Slater's Place Illusion (PI) and Plausibility Illusion (Psi) in a virtual visual cliff environment. PI (the illusion of being in a place) and Psi (the illusion that the depicted events are actually happening) were proposed by Slater as orthogonal components of virtual experience which contribute to realistic response in a VE. To that end, we identified characteristics of a virtual reality experience that we expected to influence one or the other of PI and Psi. We designed two experiments in which each participant experienced a given VE in one of four conditions chosen from a 2×2 design: high or low levels of PI-eliciting characteristics (that is, immersion) and high or low levels of Psi-eliciting characteristics. Following Skarbez, we use the term "coherence" for those characteristics which contribute to Psi, parallel to the use of "immersion" for characteristics that contribute to PI. We collected both questionnaire-based and physiological metrics. Several existing presence questionnaires could not reliably distinguish the effects of PI from those of Psi. They did, however, indicate that high levels of PI-eliciting characteristics and Psi-eliciting characteristics together result in higher presence, compared any of the other three conditions. This suggests that "breaks in PI" and "breaks in Psi" belong to a broader category of "breaks in experience," any of which result in a degraded user experience. Participants' heart rates, however, responded markedly differently in the two Psi conditions; no such difference was observed across the PI conditions. This indicates that a VE that exhibits unusual or confusing behavior can cause stress in a user that affects physiological responses, and that one must take care to eliminate such confusing behaviors if one is using physiological measurement as a proxy for subjective experience in a VE.

We report on the design and results of an experiment investigating Slater's Place Illusion (PI) and Plausibility Illusion (Psi) in a virtual visual cliff environment. Existing presence questionnaires could not reliably distinguish the effects of PI from those of Psi. They did, however, indicate that high levels of PI-eliciting characteristics and Psi-eliciting characteristics together result in higher presence, compared to any of the other three conditions. Also, participants' heart rates responded markedly differently in the two Psi conditions; no such difference was observed across the PI conditions.

We discuss the design and results of an experiment investigating Plausibility Illusion in virtual human (VH) interactions, in particular, the coherence of conversation with a VH. This experiment was performed in combination with another experiment evaluating two display technologies. As that aspect of the study is not relevant to this poster, it will be mentioned only in the Materials section. Participants who interacted with a low-coherence VH looked around the room markedly more than participants interacting with a high-coherence VH, demonstrating that the level of coherence of VHs can have a detectable effect on user behavior and that head and gaze behavior can be used to evaluate the quality of a VH interaction.

We report on the design and results of an experiment investigating factors influencing Slater's Plausibility Illusion (Psi) in virtual environments (VEs). Slater proposed Psi and Place Illusion (PI) as orthogonal components of virtual experience which contribute to realistic response in a VE. PI corresponds to the traditional conception of presence as "being there," so there exists a substantial body of previous research relating to PI, but very little relating to Psi. We developed this experiment to investigate the components of plausibility illusion using subjective matching techniques similar to those used in color science. Twenty-one participants each experienced a scenario with the highest level of coherence (the extent to which a scenario matches user expectations and is internally consistent), then in eight different trials chose transitions from lower-coherence to higher-coherence scenarios with the goal of matching the level of Psi they felt in the highest-coherence scenario. At each transition, participants could change one of the following coherence characteristics: the behavior of the other virtual humans in the environment, the behavior of their own body, the physical behavior of objects, or the appearance of the environment. Participants tended to choose improvements to the virtual body before any other improvements. This indicates that having an accurate and well-behaved representation of oneself in the virtual environment is the most important contributing factor to Psi. This study is the first to our knowledge to focus specifically on coherence factors in virtual environments.

Existing head-tracking systems all suffer from various limitations, such as latency, cost, accuracy, or drift. I propose to address these limitations by using depth cameras and existing 3D reconstruction algorithms to simultaneously localize the camera position and build a map of the environment, providing stable and drift-free tracking. This method is enabled by the recent proliferation of light-weight, inexpensive depth cameras. Because these cameras have a relatively slow frame rate, I combine this technique with a low-latency inertial measurement unit to estimate movement between frames. Using the generated environment model, I further propose a collision avoidance system for use with real walking.

The primary job of the teacher is to make learning happen; that is a design task. Most of us learned most of what we know by what we did, not by what we heard or read. A corollary is that the careful designing of exercises, assignments, projects, even quizzes, makes more difference than the construction of lectures. A second corollary is that project courses that go deeply into narrow aspects of a subject seem to stick longer and deeper than approaches aiming at comprehensive coverage. How to strike a balance? I've taught a first software engineering laboratory course 22 times, and an advanced computer architecture course about ten times. Here are some techniques that work for me.

Head motion during real walking is complex: The basic translational path is obscured by head bobbing. Many VE applications would be improved if a bobbing-free path were available. This paper introduces a model that describes head position while walking in terms of a bobbing free path and the head bobs. We introduce two methods to approximate the model from head-track data.

In order to better understand how scene motion is perceived in immersive virtual environments, we measured scene-motion thresholds under different conditions across three experiments. Thresholds were measured during quasi-sinusoidal head yaw, single left-to-right or right-to-left head yaw, different phases of head yaw, slow to fast head yaw, scene motion relative to head yaw, and two scene illumination levels. We found that across various conditions 1) thresholds are greater when the scene moves with head yaw (corresponding to gain < 1:0) than when the scene moves against head yaw (corresponding to gain > 1:0), and 2) thresholds increase as head motion increases.

We present a new method for evaluating user experience in interactions with virtual humans (VHs). We code the conversational errors made by the VH. These errors, in addition to the duration of the interaction and the numbers of statements made by the participant and the VH, provide objective, quantitative data about the virtual social interaction. We applied this method to a set of previously collected interactions between medical students and VH patients and present preliminary results. The error metrics do not correlate with traditional measures of the quality of a virtual experience, e.g. presence and copresence questionnaires. The error metrics were significantly correlated with scores on the Maastricht Assessment of Simulated Patients (MaSP), a scenario-appropriate measure of simulation quality, suggesting further investigation is warranted.

Many Virtual Environments require walking interfaces to explore virtual worlds much larger than available real-world tracked space. We present a model for generating virtual locomotion speeds from Walking-In-Place (WIP) inputs based on walking biomechanics. By employing gait principles, our model - called Gait-Understanding-Driven Walking-In-Place (GUD WIP) - creates output speeds which better match those evident in Real Walking, and which better respond to variations in step frequency, including realistic starting and stopping. The speeds output by our implementation demonstrate considerably less within-step fluctuation than a good current WIP system - Low-Latency, Continuous-Motion (LLCM) WIP - while still remaining responsive to changes in user input. We compared resulting speeds from Real Walking, GUD WIP, and LLCM-WIP via user study: The average output speeds for Real Walking and GUD WIP respond consistently with changing step frequency - LLCM-WIP is far less consistent. GUD WIP produces output speeds that are more locally consistent (smooth) and step-frequency-to-walk-speed consistent than LLCM-WIP.

When a virtual environment system prevents a user's avatar hand from penetrating virtual objects, the seen and felt positions of the hand separate. We propose a new method for reducing this position discrepancy as quickly as possible without introducing perceptible discrepancy between the seen and felt motion of the user's hand. We performed a user study to compare this new method to two previous methods of dealing with position discrepancy. Our method showed statistically significant improvements in user-reported naturalness and user preference and showed no loss in user performance

We investigated the ability of a user in a head-mounted display virtual environment to detect a virtual hand avatar moving at a speed different than that of the real hand. We measured discrepancy detection thresholds for each of the six cardinal directions of 3-space (left, right, up, down, toward, and away). For each of these six directions we measured two discrepancy detection thresholds: one for when the avatar hand moved more quickly than the real hand and one for when it moved more slowly. We found a trend that users are less sensitive to increases in hand avatar speed than they are to decreases. The amount the hand avatar speed can be increased without a user noticing is surprisingly large. This information is useful for techniques that require introducing hand-avatar motion discrepancy, such as a technique for recovering from the position discrepancy introduced by simulated surface constraints.

Figure 1. A participant who believes he is aiming at the virtual game board directly in front of him. Without force feedback, a head-mounted display user's avatar may penetrate virtual objects. Some virtual environment designers prevent visual interpenetration, making the assumption that prevention improves user experience. However, preventing visual avatar interpenetration causes discrepancy between visual and proprioceptive cues. We investigated users ’ detection thresholds for visual interpenetration (the depth at which they see that two objects have interpenetrated) and sensory discrepancy (the displacement at which they notice mismatched visual and proprioceptive cues). We found that users are much less sensitive to visual-proprioceptive conflict than they are to visual interpenetration. We present our plan for using this result to create a better technique for dealing with virtual object penetration.

To compare and evaluate locomotion interfaces for users who are (virtually) moving on foot in VEs, we performed a study to characterize task behavior and task performance with different visual and locomotion interfaces. In both a computer-generated environment and a corresponding real environment, study participants walked to targets on walls and stopped as close to them as they could without making contact. In each of five experimental conditions participants used a combination of one of three locomotion interfaces (really walking, walking-in-place, and joystick flying), and one of three visual conditions (head-mounted display, unrestricted natural vision, or field-of-view-restricted natural vision). We identified metrics and collected data that captured task performance and the underlying kinematics of the task. Our results show: 1) Over 95% of the variance in simple motion paths is captured in three critical values: peak velocity; when, in the course of a motion, the peak velocity occurs; and peak deceleration. 2) Correlations of those critical value data for the conditions taken pairwise suggest a coarse ordering of locomotion interfaces by 3) Task performance varies with interface condition, but correlations of that value for conditions taken pairwise do not cluster by naturalness. 4) The perceptual variable, r (also known as the time-to-contact) calculated at the point of peak deceleration has higher correlation with task performance than r calculated at peak velocity.

We present algorithms that enable virtual objects to interact with and respond to virtual representations, avatars, of real objects. These techniques allow dynamic real objects, such as the user, tools, and parts, to be visually and physically incorporated into the virtual environment (VE). The system uses image-based object reconstruction and a volume query mechanism to detect collisions and to determine plausible collision responses between virtual objects and the avatars. This allows our system to provide the user natural interactions with the VE.We have begun a collaboration with NASA Langley Research Center to apply the hybrid environment system to a satellite payload assembly verification task. In an informal case study, NASA LaRC payload designers and engineers conducted common assembly tasks on payload models. The results suggest that hybrid environments could provide significant advantages for assembly verification and layout evaluation tasks.

Immersive virtual environments (VEs) provide participants with computer-generated environments filled with virtual objects to assist in learning, training, and practicing dangerous and/or expensive tasks. But for certain tasks, does having every object being virtual inhibit the interactivity? Further, does the virtual object's visual fidelity affect performance? Overall VE effectiveness may be reduced if users spend most of their time and cognitive capacity learning how to interact and adapting to interacting with a purely virtual environment. We investigated how handling real objects and how self-avatar visual fidelity affects performance on a spatial cognitive task in an immersive VE. We compared participants' performance on a block arrangement task in both a real-space environment and several virtual and hybrid environments. The results showed that manipulating real objects in a VE brings task performance closer to that of real space, compared to manipulating virtual objects.

Previous research has shown that even low end-to-end latency can have adverse effects on performance in virtual environments (VE). This paper reports on an experiment investigating the effect of latency on other metrics of VE effectiveness: physiological response, simulator sickness, and self-reported sense of presence. The VE used in the study includes two rooms: the first is normal and non-threatening; the second is designed to evoke a fear/stress response. Participants were assigned to either a low latency (/spl sim/50 ms) or high latency (/spl sim/90 ms) group. Participants in the low latency condition had a higher self-reported sense of presence and a statistically higher change in heart rate between the two rooms than did those in the high latency condition. There were no significant relationships between latency and simulator sickness.

No abstract available.

No abstract available.

A common measure of the quality or effectiveness of a virtual environment (VE) is the mount of presence it evokes in users. Presence is often defined as the sense of being there in a VE. There has been much debate about the best way to measure presence, and presence researchers need, and have sought, a measure that is reliable, valid, sensitive, and objective. We hypothesized that to the degree that a VE seems real, it would evoke physiological responses similar to those evoked by the corresponding real environment, and that greater presence would evoke a greater response. To examine this, we conducted three experiments, the results of which support the use of physiological reaction as a reliable, valid, sensitive, and objective presence measure. The experiments compared participants' physiological reactions to a non-threatening virtual room and their reactions to a stressful virtual height situation. We found that change in heart rate satisfied our requirements for a measure of presence, change in skin conductance did to a lesser extent, and that change in skin temperature did not. Moreover, the results showed that inclusion of a passive haptic element in the VE significantly increased presence and that for presence evoked: 30FPS > 20FPS > 15FPS.

We present a system for rendering very complex 3D models at interactive rates.We select a subset of the model as preferred viewpoints and partition the space into virtual cells.Each cell contains near geometry, rendered using levels of detail and visibility culling, and far geometry, rendered as a textured depth mesh.Our system automatically balances the screen-space errors resulting from geometric simplification with those from textureddepth-mesh distortion.We describe our prefetching and data management schemes, both crucial for models significantly larger than available system memory.We have successfully used our system to accelerate walkthroughs of a 13 million triangle model of a large coal-fired power plant and of a 1.7 million triangle architectural model.We demonstrate the walkthrough of a 1.3 GB power plant model with a 140 MB cache footprint.

A study by Slater, et al., [1995] indicated that naive subjects in an immersive virtual environment experience a higher subjective sense of presence when they locomote by walking-in-place (virtual walking) than when they push-button-fly (along the floor plane).We replicated their study, adding real walking as a third condition.Our study confirmed their findings.We also found that real walking is significantly better than both virtual walking and flying in ease (simplicity, straightforwardness, naturalness) as a mode of locomotion.The greatest difference in subjective presence was between flyers and both kinds of walkers.In addition, subjective presence was higher for real walkers than virtual walkers, but the difference was statistically significant only in some models.Follow-on studies show virtual walking can be substantially improved by detecting footfalls with a head accelerometer.As in the Slater study, subjective presence significantly correlated with subjects' degree of association with their virtual bodies (avatars).This, our strongest statistical result, suggests that substantial potential presence gains can be had from tracking all limbs and customizing avatar appearance.An unexpected by-product was that real walking through our enhanced version of Slater's visual-cliff virtual environment (Figure 1) yielded a strikingly compelling virtual experience-the strongest we and most of our visitors have yet experienced.The most needed system improvement is the substitution of wireless technology for all links to the user.

Ivan Sutherland first proposed virtual reality in 1965, and in the next few years built a working system. Twenty years later, line-drawing hardware, the Polhemus tracker, and LCD tiny-TV displays made VR feasible, if costly and inadequate, for several explorers. In 1990, journalists jumped on the idea, and hype levels went out of sight. As usual with infant technologies, the realization of the early dreams and the harnessing to real work has taken longer than the wild prognostications, but it is now happening. I survey the current state-of-the-art, addressing the perennial questions of technology and applications.

Manipulation in immersive virtual environments is difficult partly because users must do without the haptic contact with real objects they rely on in the real world to orient themselves and their manipulanda. To compensate for this lack, we propose exploiting the one real object every user has in a virtual environment, his body. We present a unified framework for virtual-environment interaction based on proprioception, a person's sense of the position and orientation of his body and limbs. We describe three forms of body-relative interaction: • Direct manipulation—ways to use body sense to help control manipulation • Physical mnemonics—ways to store/recall information relative to the body • Gestural actions—ways to use body-relative actions to issue commands Automatic scaling is a way to bring objects instantly within reach so that users can manipulate them using proprioceptive cues. Several novel virtual interaction techniques based upon automatic scaling and our proposed framework of proprioception allow a user to interact with a virtual world intuitively, efficiently, precisely, and lazily. We report the results of both informal user trials and formal user studies of the usability of the body-relative interaction techniques presented. CR

Since 1991, our team of computer scientists, chemists and physicists have worked together to develop an advanced, virtual-environment interface to scanned-probe microscopes. The interface has provided insights and useful capabilities well beyond those of the traditional interface. This paper lists the particular visualization and control techniques that have enabled actual scientific discovery, including specific examples of insight gained using each technique. This information can help scientists determine which features are likely to be useful in their particular application, and which would be just sugar coating. It can also guide computer scientists to suggest the appropriate type of interface to help solve a particular problem. We have found benefit in advanced rendering with natural viewpoint control (but not always), from semi-automatic control techniques, from force feedback during manipulation, and from storing/replaying data for an entire experiment. These benefits come when the system is well-integrated into the existing tool and allows export of the data to standard visualization packages.

We propose the idea of simplification envelopes for generating a hierarchy of level-of-detail approximations for a given polygonal model.Our approach guarantees that all points of an approximation are within a user-specifiable distance from the original model and that all points of the original model are within a distance from the approximation.Simplification envelopes provide a general framework within which a large collection of existing simplification algorithms can run.We demonstrate this technique in conjunction with two algorithms, one local, the other global.The local algorithm provides a fast method for generating approximations to large input meshes (at least hundreds of thousands of triangles).The global algorithm provides the opportunity to avoid local "minima" and possibly achieve better simplifications as a result.Each approximation attempts to minimize the total number of polygons required to satisfy the above constraint.The key advantages of our approach are: General technique providing guaranteed error bounds for genus-preserving simplification Automation of both the simplification process and the selection of appropriate viewing distances Prevention of self-intersection Preservation of sharp features Allows variation of approximation distance across different portions of a model CR Categories and Subject Descriptors: I.3.

A parallel, analytic approach for defining and computing the inter and intra molecular interfaces in three dimensions is described. The molecular interface surfaces are derived from approximations to the power diagrams over the participating molecular units. For a given molecular interface our approach can generate a family of interface surfaces parametrized by /spl alpha/ and /spl beta/, where /spl alpha/ is the radius of the solvent molecule (also known as the probe radius) and /spl beta/ is the interface radius that defines the size of the molecular interface. Molecular interface surfaces provide biochemists with a powerful tool to study surface complementarity and to efficiently characterize the interactions during a protein substrate docking. The complexity of our algorithm for molecular environments is O(nk log/sup 2/ k), where n is the number of atoms in the participating molecular units and k is the average number of neighboring atoms-a constant, given /spl alpha/ and /spl beta/.

An interactive visualization of weighted three-dimensional alpha-hulls is presented for static and dynamic spheres. The alpha-hull is analytically computed and represented by a triangulated mesh. The entire surface is computed and displayed in real-time at interactive rates. The weighted three-dimensional alpha-hulls are equivalent to smooth molecular surfaces of biochemistry. Biochemistry applications of interactive computation and display of alpha-hulls or smooth molecular surfaces are outlined.

No abstract available.

Article Free Access Share on VIEW: an exploratory molecular visualization system with user-definable interaction sequences Authors: Lawrence D. Bergman View Profile , Jane S. Richardson View Profile , David C. Richardson View Profile , Frederick P. Brooks View Profile Authors Info & Claims SIGGRAPH '93: Proceedings of the 20th annual conference on Computer graphics and interactive techniquesSeptember 1993 Pages 117–126https://doi.org/10.1145/166117.166132Published:01 September 1993Publication History 14citation526DownloadsMetricsTotal Citations14Total Downloads526Last 12 Months17Last 6 weeks1 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF

We present an atomic-scale teleoperation system that uses a head-mounted display and force-feedback manipulator arm for a user interface and a Scanning Tunneling Microscope (STM) as a sensor and effector.The system approximates presence at the atomic scale, placing the scientist on the surface, in control, w h i l e the experiment is happening.A scientist using the Nanomanipulator can view incoming STM data, feel the surface, and modify the surface (using voltage pulses) in real time.The Nanomanipulator has been used to study the effects of bias pulse duration on the creation of gold mounds.We intend to use the system to make controlled modifications to silicon surfaces.

An algorithm for rapid computation of Richards's smooth molecular surface is described. The entire surface is computed analytically, triangulated, and displayed at interactive rates. The faster speeds for our program have been achieved by algorithmic improvements, paralleling the computations, and by taking advantage of the special geometrical properties of such surfaces. Our algorithm is easily parallelable and it has a time complexity of O (k log k) over n processors, where n is the number of atoms of the molecule and k is the average number of neighbors per atom.>

Two strategies, pre-computation before display and adaptive refinement during display, are used to combine interactivity with high image quality in a virtual building simulation. Pre-computation is used in two ways. The hidden-surface problem is partially solved by automatically pre-computing potentially visible sets of the model for sets of related viewpoints. Rendering only the potentially visible subset associated with the current viewpoint, rather than the entire model, produces significant speedups on real building models. Solutions for the radiosity lighting model are pre-computed for up to twenty different sets of lights. Linear combinations of these solutions can be manipulated in real time. We use adaptive refinement to trade image realism for interactivity as the situation requires. When the user is stationary we replace a coarse model using few polygons with a more detailed model. Image-level linear interpolation smooths the transition between differing levels of image realism.

This paper is about using the sense of touch, the hapti c system, as part of our everyday interface wit h computationally created worlds .In Part I, we discuss a particular system, called Sandpaper, designed for experimenting with feeling texture .In part II, we discuss how control analysis helps us understand th e behavior of the types of hardware and software we use t o implement force display .We will not comprehensively review the literature of forc e display devices and their applications; descriptions can b e found in e .g .[Sutherland651, [No11721, [Batter721 , [Atkinson77l, [Brooks88j, [Ouh-young881, [Smith881 , Part IForce display technology works by using mechanica l actuators to apply forces to the user, By simulating th e physics of the user's virtual world, we compute these forces in real-time, then send them to the actuators so that the user feels them, The force display technology we use in th e Sandpaper system is a motor-driven two-degree of freedo m joystick (built by Max Behensky and Doug Milliken) .Th e joystick position is reported to the software, whic h computes the appropriate forces for the joystick's motors .Why create texture?Force display is especially useful for communicating surfac e texture and bulk properties of objects and environments a s well as dynamics of objects .In this way force display technologies augment the strengths of computer-generate d graphics and sound in creating convincingly realistic environments (figures 1, 4) .In the Sandpaper system, we use a novel technique to allo w the user to feel textures .We create very small virtua l

We began in 1967 a project to develop a haptic+display for 6-D force fields of interacting protein molecules. We approached it in four stages: a 2-D system, a 3-D system tested with a simple task, a 6-D system tested with a simple task, and a full 6-D molecular docking system, our initial goal. This paper summarizes the entire project---the four systems, the evaluation experiments, the results, and our observations. The molecular docking system results are new.Our principal conclusions are:• Haptic display as an augmentation to visual display can improve perception and understanding both of force fields and of world models populated with impenetrable objects.• Whereas man-machine systems can outperform computer-only systems by orders of magnitude on some problems, haptic-augmented interactive systems seem to give about a two-fold performance improvement over purely graphical interactive systems. Better technology may give somewhat more, but a ten-fold improvement does not seem to be in the cards.• Chemists using GROPE-III can readily reproduce the true docking positions for drugs whose docking is known (but not to them) and can find very good docks for drugs whose true docks are unknown. The present tool promises to yield new chemistry research results; it is being actively used by research chemists.• The most valuable result from using GROPE-III for drug docking is probably the radically improved situation awareness that serious users report. Chemists say they have a new understanding of the details of the receptor site and its force fields, and of why a particular drug docks well or poorly.• We see various scientific/education applications for haptic displays but believe entertainment, not scientific visualization, will drive and pace the technology.• The hardware-software system technology we have used is barely adequate, and our experience sets priorities for future development.• Some unexpected perceptual phenomena were observed. All of these worked for us, not against us.

A simplified docking problem is studied. The user attempts to find the potential-energy minimum in a 6-D space defined by six Hooke's-law springs attached to a manipulable object. This space has no other local minima. A pilot-controlled experiment with seven subjects, twelve trials each, showed that performance with a force display is better (p>

I treat three related subjects: virtual-worlds research—the construction of real-time 3-D illusions by computer graphics; some observations about interfaces to virtual worlds; and the coming application of virtual-worlds techniques to the enhancement of scientific computing.

A real-time molecular docking system is developed that uses an electrically coupled remote manipulator as a force display. The system, which uses integrates interactive computer graphics and high-speed calculation of the interaction forces between a drug and a receptor site in a molecule, is designed to be a tool for molecular scientists. The manipulator is used to generate the forces and torques exerted on the drug molecule when it is aligned with the receptor site by the user's hand. The manipulator serves both as an input device for 6-D manipulation and as an output device for generating forces. Preliminary testing indicates that the system might enhance the biochemist's understanding and performance.>

Pixel-planes is a logic-enhanced memory system for raster graphics and imaging. Although each pixel-memory is enhanced with a one-bit ALU, the system's real power comes from a tree of one-bit adders that can evaluate linear expressions Ax+By+C for every pixel (x,y) simultaneously, as fast as the ALUs and the memory circuits can accept the results. We and others have begun to develop a variety of algorithms that exploit this fast linear expression evaluation capability. In this paper we report some of those results. Illustrated in this paper is a sample image from a small working prototype of the Pixel-planes hardware and a variety of images from simulations of a full-scale system. Timing estimates indicate that 30,000 smooth shaded triangles can be generated per second, or 21,000 smooth-shaded and shadowed triangles can be generated per second, or over 25,000 shaded spheres can be generated per second. Image-enhancement by adaptive histogram equalization can be performed within 4 seconds on a 512x512 image.

A data-handling unit is described which permits binary or decimal arithmetic to be performed on data fields of any length from one to sixty-four bits. Within the field, character structure can be further specified: these processing entities, called bytes, may be from one to eight bits long. Fields may be stored with or without algebraic sign. On all operations, the relative offset or shift between the operand from memory and that from the accumulator can be specified. Besides the arithmetic operations, three new logical instructions allow any of the sixteen logical connectives of two variables to operate upon each pair of bits in the memory and accumulator operands. The variable field length, variable byte-size features, extend the use of connective operations to a surprisingly wide variety of logical, house-keeping, and editing tasks. These arithmetic and connective instructions are general and powerful programming tools which greatly simplify complex manipulations. Programming of typical tasks, with both the new instructions and with the instruction set of a conventionally-organized computer, has shown that the new set requires substantially fewer instructions to be written, stored, and executed. Furthermore, the new instruction set has considerably fewer distinct operations than the more conventional set. This is possible because the general-purpose instructions of the new set replace many ad hoc instructions which deal with pieces of instructions or data words, or which perform shifting, packing, or editing functions. The initial application of the variable field length data-processing unit is in the IBM Stretch computer.

The high-order probabilities of element sequences can be determined from a sample of linear structures and can be used for synthesis of new structures. From theoretical considerations one can identify the qualitative conditions for satisfactory output. The theoretical concepts can be tested and quantitative parameters determined by experiment. Such an experiment has been performed by analyzing written music and by testing the analysis through the synthesis of new musical compositions, using a digital computer. A sample of 37 melodies was analyzed for the probabilities of the elements, element pairs (digrams), trigrams, and so on to the eighth order. The tables derived were used for the synthesis of original melodies by a random process. The theory and the experimental verification are considered in detail. The experimental results presented include comparative statistics of the successful syntheses using each of the eight orders of analysis, examples of melodies generated by low, medium, and high-order synthesis, and confirmation of degeneracy and other effects predicted by the theory.