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"The Origins of Computer Graphics in Europe," is being published in two parts: Part 1, published in the March/April issue of IEEE Computer Graphics and Applications (IEEE CG&A), is subtitled "The Beginnings in Germany"; Part 2, published in this May/June 2023 issue, is subtitled "The Early Spreading of Computer Graphics in Europe." I was a participant, contributor, and witness to the events reported here and I relate my personal story along with the broader history. Part 1 describes the origins and successful evolution of computer graphics in Germany, starting in 1965, and includes details of the people and subject matter of the earliest research groups. It describes the efforts undertaken to establish computer graphics as a proper academic discipline, including the founding of EUROGRAPHICS, and creation of institutes for both basic and applied research in computer graphics. Part 2 continues the story with a focus on activities contributing to the growth of the academic and industrial computer graphics communities across Europe and documents the two IFIP workshops held at Seillac and the development of the GKS Graphics Standard. Over the years, computer graphics gained respect and importance as a component of the computer science curricula and became an important tool and enabling technology for applications for industry and for the IT market in Europe.

"The Origins of Computer Graphics in Europe," is being published in two parts: Part 1, in this issue of IEEE Computer Graphics and Applications, is subtitled "The Beginnings in Germany"; Part 2, to be published in the May/June issue, is subtitled "The Spreading of Computer Graphics in Europe." I was a participant, contributor, and witness to the events reported here and I relate my personal story along with the broader history. Part 1 describes the origins and successful evolution of computer graphics in Germany, starting in 1965, and includes details of the people and subject matter of the earliest research groups. It describes the efforts undertaken to establish computer graphics as a proper academic discipline, including the founding of EUROGRAPHICS, and creation of institutes for both basic and applied research in computer graphics. Part 2 continues the story with a focus on activities contributing to the growth of the academic and industrial computer graphics communities across Europe and documents the two IFIP workshops at Seillac and the development of the GKS Graphics Standard. Over these years, computer graphics gained respect and importance as a component of the computer science curricula and became an important tool and enabling technology for applications for industry and for the IT market in Europe.

The article describes my long journey as a Jewish-born hidden child who was handed over to a Catholic family before the Krakow ghetto was eliminated in 1943. My father survived and I was reunited with him. We traveled to Germany in 1950 and were accepted as Canadian refugees in 1952. After an undergraduate and graduate program at McGill University, I was married in an Episcopalian/Anglican ceremony. My good fortune continued when I joined a research group at the National Research Council in the 1960s. The group worked on computer graphics and computer animation and won a Technical Academy Award for technology for the animated short Hunger/La Faim.

The thrill of scientific discovery, the excitement of engineering development, and the fresh thinking of design explorations were invigorating as we participated in the birth of a new discipline: Information Visualization. This discipline, based on graphical user interfaces with pointing devices, became possible as software matured, hardware sped up, and screen resolution improved. Driven by the concepts of direct manipulation and dynamic queries, we made interactive interfaces that empowered users and opened up new possibilities for the next generation of designers. We worked with professionals who had real problems and tested real users to get their feedback. Some projects failed and some papers never got published, but many of the new ideas found their way into widely used commercial products. Our great satisfaction is that our students have spread the community spirit of the Human-Computer Interaction Laboratory as they continue to make further contributions.

Visualization, interactive computer graphics, and related topics have been a particularly dynamic area of computer science, producing advances that impact society. Working at times in a research laboratory and at times for two science funding agencies, I held positions at the level of an individual researcher, Director of a VR Laboratory, and funding agency Program Director. This article will discuss some of my experiences, including insight into how science programs in funding agencies are initiated.

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.

This work addresses cybersickness, a major barrier to successful long-exposure immersive virtual reality (VR) experiences since user discomfort frequently leads to prematurely ending such experiences. Starting from sensory conflict theory, we posit that if a vibrating floor delivers vestibular stimuli that minimally match the vibration characteristics of a scenario, the size of the conflict between the visual and vestibular senses will be reduced and, thus, the incidence and/or severity of cybersickness will also be reduced. We integrated a custom-built, computer-controlled vibrating floor in our VR system. To evaluate the system, we implemented a realistic off-road vehicle driving simulator in which participants rode multiple laps as passengers on an off-road course. We programmed the floor to generate vertical vibrations similar to those experienced in real off-road vehicle travel. The scenario and driving conditions were designed to be cybersickness-inducing for users in both the Vibration and No-vibration conditions. We collected subjective and objective data for variables previously shown to be related to levels of cybersickness or presence. These included presence and simulator sickness questionnaires (SSQ), self-rated discomfort levels, and the physiological signals of heart rate, galvanic skin response (GSR), and pupil size. Comparing data between participants in the Vibration group (N=11) to the No-Vibration group (N=11), we found that Delta-SSQ Oculomotor response and the GSR physiological signal, both known to be positively correlated with cybersickness, were significantly lower (with large effect sizes) for the Vibration group. Other variables differed between groups in the same direction, but with trivial or small effect sizes. The results indicate that the floor vibration significantly reduced some measures of cybersickness.

The research and production of computer graphics imagery and animation at The Ohio State University started with the artistic work of Prof. Charles Csuri. He developed the Computer Graphics Research Group in response to the award of a National Science Foundation Grant in 1974, and the group transferred its technology to a commercial production effort, Cranston/Csuri Productions, Inc., in 1981. CGRG evolved into the Advanced Computing Center for the Arts and Design in 1987. This article provides an historical review of the significant activities of these groups.

Computer graphics has a long history. Industrial organizations and laboratories drove significant improvements as they adapted and assembled basic capabilities into complex interactive applications. Of particular concern in the early days was providing interactive 3-D applications for computer-aided design and engineering. This article describes the experience of two early industry practitioners who built successful 1970s interactive 3-D systems.

The Marching Cubes paper by Bill Lorensen and Harvey Cline, "Marching Cubes: A High Resolution 3D Surface Construction Algorithm," was published at SIGGRAPH 1987.1 According to Google Scholar, their paper has 15,667 citations (as of January 17, 2020), the most highly cited paper in computer graphics. Sadly, while writing this article Bill Lorensen passed away on December 12, 2019. Origins Department Editor Chris Johnson contributed the text in italics. EARLY.

Global illumination refers to a complete shading model that simulates real lighting and reflection as accurately as possible. Whether used for product prototyping or special effects for entertainment, the goal is to match the appearance of the real world. The origins of global illumination come at the intersection of a steady progression of shading models with the ancient simulation technique of ray tracing.

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.

Redirected Touching is a technique in which virtual space is warped to map many virtual objects onto one real object that serves as a passive haptic prop. Recent work suggests that this mapping can often be predictably unnoticeable and have little effect on task performance. We investigated training and adaptation on a rapid aiming task in a real environment, an unwarped virtual environment, and a warped virtual environment. Participants who experienced a warped virtual space reported an initial strange sensation, but adapted to the warped space after short repeated exposure. Our data indicate that all the virtual training was less effective than real-world training, but after adaptation, participants trained as well in a warped virtual space as in an unwarped one.

Redirected Free Exploration with Distractors (RFEDs) is a large-scale real-walking locomotion interface developed to enable people to walk freely in Virtual Environments (VEs) that are larger than the tracked space in their facility. This paper describes the RFED system in detail and reports on a user study that evaluated RFED by comparing it to Walking-in-Place (WIP) and Joystick (JS) interfaces. The RFED system is composed of two major components, redirection and distractors. This paper discusses design challenges, implementation details, and lessons learned during the development of two working RFED systems. The evaluation study examined the effect of the locomotion interface on users' cognitive performance on navigation and wayfinding measures. The results suggest that participants using RFED were significantly better at navigating and wayfinding through virtual mazes than participants using walking-in-place and joystick interfaces. Participants traveled shorter distances, made fewer wrong turns, pointed to hidden targets more accurately and more quickly, and were able to place and label targets on maps more accurately, and more accurately estimate the virtual environment size.

Background and Purpose: Persistent deficits in gait speed and spatiotemporal symmetry are prevalent following stroke and can limit the achievement of community mobility goals. Rehabilitation can improve gait speed, but has shown limited ability to improve spatiotemporal symmetry. The incorporation of combined visual and proprioceptive feedback regarding spatiotemporal symmetry has the potential to be effective at improving gait., Case Description: A 60-year-old man (18 months poststroke) and a 53-year-old woman (21 months poststroke) each participated in gait training to improve gait speed and spatiotemporal symmetry. Each patient performed 18 sessions (6 weeks) of combined treadmill-based gait training followed by overground practice. To assist with relearning spatiotemporal symmetry, treadmill-based training for both patients was augmented with continuous, real-time visual and proprioceptive feedback from an immersive virtual environment and a dual belt treadmill, respectively., Outcomes: Both patients improved gait speed (patient 1: 0.35 m/s improvement; patient 2: 0.26 m/s improvement) and spatiotemporal symmetry. Patient 1, who trained with step-length symmetry feedback, improved his step-length symmetry ratio, but not his stance-time symmetry ratio. Patient 2, who trained with stance-time symmetry feedback, improved her stance-time symmetry ratio. She had no step-length asymmetry before training., Discussion: Both patients made improvements in gait speed and spatiotemporal symmetry that exceeded those reported in the literature. Further work is needed to ascertain the role of combined visual and proprioceptive feedback for improving gait speed and spatiotemporal symmetry after chronic stroke.

Slow gait speed and interlimb asymmetry are prevalent in a variety of disorders. Current approaches to locomotor retraining emphasize the need for appropriate feedback during intensive, task-specific practice. This paper describes the design and feasibility testing of the integrated virtual environment rehabilitation treadmill (IVERT) system intended to provide real-time, intuitive feedback regarding gait speed and asymmetry during training. The IVERT system integrates an instrumented, split-belt treadmill with a front-projection, immersive virtual environment. The novel adaptive control system uses only ground reaction force data from the treadmill to continuously update the speeds of the two treadmill belts independently, as well as to control the speed and heading in the virtual environment in real time. Feedback regarding gait asymmetry is presented 1) visually as walking a curved trajectory through the virtual environment and 2) proprioceptively in the form of different belt speeds on the split-belt treadmill. A feasibility study involving five individuals with asymmetric gait found that these individuals could effectively control the speed of locomotion and perceive gait asymmetry during the training session. Although minimal changes in overground gait symmetry were observed immediately following a single training session, further studies should be done to determine the IVERT's potential as a tool for rehabilitation of asymmetric gait by providing patients with congruent visual and proprioceptive feedback.

We report on a user study evaluating Redirected Free Exploration with Distractors (RFED), a large-scale, real-walking, locomotion interface, by comparing it to Walking-in-Place (WIP) and Joystick (JS), two common locomotion interfaces. The between-subjects study compared navigation ability in RFED, WIP, and JS interfaces in VEs that are more than two times the dimensions of the tracked space. The interfaces were evaluated based on navigation and wayfinding metrics and results suggest that participants using RFED were significantly better at navigating and wayfinding through virtual mazes than participants using walking-in-place and joystick interfaces. Participants traveled shorter distances, made fewer wrong turns, pointed to hidden targets more accurately and more quickly, and were able to place and label targets on maps more accurately. Moreover, RFED participants were able to more accurately estimate VE size.

What are desirable and undesirable features of virtual-environment (VE) software architectures? What should be present (and absent) from such systems if they are to be optimally useful? How should they be structured? To help answer these questions we present experience from application designers, toolkit designers, and VE system architects along with examples of useful features from existing systems. Topics are organized under the major headings of: 3D space management, supporting display hardware, interaction, event management, time management, computation, portability, and the observation that less can be better. Lessons learned are presented as discussion of the issues, field experiences, nuggets of knowledge, and case studies.

Users in virtual environments often find navigation more difficult than in the real world. Our new locomotion interface, Improved Redirection with Distractors (IRD), enables users to walk in larger-than-tracked space VEs without predefined waypoints. We compared IRD to the current best interface, really walking, by conducting a user study measuring navigational ability. Our results show that IRD users can really walk through VEs that are larger than the tracked space and can point to targets and complete maps of VEs no worse than when really walking.

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.

Virtual Environments (VEs) that use a real-walking locomotion interface have typically been restricted in size to the area of the tracked lab space. Techniques proposed to lift this size constraint, enabling real walking in VEs that are larger than the tracked lab space, all require reorientation techniques (ROTs) in the worst-case situation-when a user is close to walking out of the tracked space. We propose a new ROT using visual and audial distractors-objects in the VE that the user focuses on while the VE rotates-and compare our method to current ROTs through three user studies. ROTs using distractors were preferred and ranked more natural by users. Our findings also suggest that improving visual realism and adding sound increased a user's feeling of presence. Users were also less aware of the rotating VE when ROTs with distractors were used. Our findings also suggest that improving visual realism and adding sound increased a user's feeling of presence.

Context: Virtual reality environments may allow researchers to investigate functional balance performance without risks associated with testing in the real world., Objective: To investigate the effects of the mass of a head-mounted display (HMD) on balance performance., Design: Counterbalanced pretest-posttest., Setting: Virtual reality laboratory., Participants: 20 healthy college students., Intervention(s): Balance Error Scoring System (BESS) with a tracker-only headband and again with tracker plus HMD was performed., Main Outcome Measures: BESS error scores, elliptical sway area, and center of pressure travel distance were recorded., Results: No effect of the HMD mass on balance performance was observed. A significant stance by surface interaction was present but was negated when the HMD conditions were included in the model., Conclusions: The mass of a HMD has not been proven to adversely affect balance performance. These data suggest the HMD mass is not a contraindication to the use of immersive virtual environments in future concussion research involving balance.