Anderson Maciel

• Ph. D.
• Professor (Associate) at University of Lisbon

The efficient, natural and precise selection and manipulation of nearby objects in 3D environments is yet a challenge in the area of 3D interaction. Robot teleoperation is a potential application field for this kind of interaction and a difficult task. In part due to the low quality of the information delivered to the operator, but also because of...

The FLS training tool box has now been adopted by the Society of Gastrointestinal Endoscopic Surgeons (SAGES) as an official training tool for minimally invasive procedures. To overcome the limitations of the physical FLS training tool box, we have developed a Virtual Basic Laparoscopic Skill Trainer (VBLaSTTM) system, which is a 3D simulator that...

In this paper, we introduce a novel "dynamic point" algorithm for computing the interaction of a line-shaped haptic cursor and polygonal surface models which has a near constant complexity. The algorithm is applied in laparoscopic surgery simulation for interaction of surgical instruments with physics-based deformable organ models.

As head-mounted displays (HMDs) with eye-tracking become increasingly accessible, the need for effective gaze-based interfaces in virtual reality (VR) grows. Traditional gaze- or hand-based navigation often limits user precision or impairs free viewing, making multitasking difficult. We present a gaze-hand steering technique that combines eye-track...

As head-mounted displays (HMDs) with eye-tracking become increasingly accessible, the need for effective gaze-based interfaces in virtual reality (VR) grows. Traditional gaze- or hand-based navigation often limits user precision or impairs free viewing, making multitasking difficult. We present a gaze-hand steering technique that combines eye-track...

Current endoscopy simulators oversimplify navigation and interaction within tubular anatomical structures to maintain interactive frame rates, neglecting the intricate dynamics of permanent contact between the organ and the medical tool. Traditional algorithms fail to represent the complexities of long, slender, deformable tools like endoscopes and...

Telepresence VR systems allow for face-to-face communication, promoting the feeling of presence and understanding of nonverbal cues. However, when discussing virtual 3D objects, limitations to presence and communication cause deictic gestures to lose meaning due to disparities in orientation. Current approaches use shared perspective, and avatar ov...

Desktop-based virtual colonoscopy is a proven and accurate process for identifying colon abnormalities. However, it is time-consuming. Faster, immersive interfaces for virtual colonoscopy are still incipient and need to be better understood. This article introduces a novel design that leverages VR paradigm components to enhance the efficiency and e...

X-ray imaging plays a crucial role in diagnostic medicine. Yet, a significant portion of the global population lacks access to this essential technology due to a shortage of trained radiologists. Eye-tracking data and deep learning models can enhance X-ray analysis by mapping expert focus areas, guiding automated anomaly detection, optimizing workf...

There is a strong demand for virtual reality (VR) to bring quality healthcare to underserved populations. This paper addresses this need with the design and prototype of SURVIVRS: Surround Video-Based Virtual Reality for Surgery Guidance. SURVIVRS allows a remote specialist to guide a local surgery team through a virtual reality (VR) telepresence i...

This paper proposes a novel multimodal DL architecture incorporating medical images and eye-tracking data for abnormality detection in chest x-rays. Our results show that applying eye gaze data directly into DL architectures does not show superior predictive performance in abnormality detection chest X-rays. These results support other works in the...

Desktop-based virtual colonoscopy has been proven to be an asset in the identification of colon anomalies. The process is accurate, although time-consuming. The use of immersive interfaces for virtual colonoscopy is incipient and not yet understood. In this work, we present a new design exploring elements of the VR paradigm to make the immersive an...

Using virtual environments (VEs) is a safer and cost-effective alternative to training people in different contexts. Immersive Virtual Reality (VR), combined with game aspects, have the potential to improve the user experience in the VE by increasing realism, engagement, and motivation. In education, there is a consensus about its contribution in t...

We present a visuo-haptic interaction approach that augments the visual experience of graphic data visualization with meaningful vibrotactile information. The user of our interface explores charts and graphs on a conventional video monitor or other displays, e.g. projection, or printed paper. When a user touches the data visualization, an array of...

The Visualization, Interaction, and Simulation Laboratory (VISLab) at UFRGS is majorly concerned with data visualization and human-computer interaction research. Research on data visualization focuses on the development of information visualization techniques and their application to different domains. Studies on interaction emphasize non-conventio...

The effectiveness of a virtual reality experience is strongly affected by the sense of presence of the users involved. This article reviews the different definitions of presence and the main proposed methods to measure it through the analysis of 1,214 papers published in the past 30 years. From the analysis of 239 user studies, we found that 85.8%...

In the real world, the sense of sight is dominant for humans, and having a normal vision is essential to perform well in many common tasks. There, ophthalmology has several tools to assess and correct a person’s vision. In VR, when wearing an HMD, even a user with normal vision is challenged by additional hurdles that affect the virtual environment...

In the context of raising awareness to assistive technologies, we propose a gaming experience that allows users to embody having a visual impairment. By occluding the user’s vision and providing spatialized audio and passive haptic feedback, allied with a speech recognition digital assistant, our goal is to present a multi-sensory experience that o...

In the context of promoting a sense of empathy for the difference in people without disabilities, we propose a gaming experience that allows users to embody having a visual impairment. By occluding the user’s vision and providing spatialized audio and passive haptic feedback, allied with a speech recognition digital assistant, our goal is to offer...

The Visualization, Interaction and Simulation Laboratory (VISLab) is part of the Computer Graphics, Image Processing and Interaction research group, which started its activities in 1978 developing projects mainly on rendering and animation. Along the years, as new researchers joined the group, new research fields such as image acquisition and analy...

The Visualization, Interaction and Simulation Laboratory (VISLab) is part of the Computer Graphics, Image Processing and Interaction research group, which started its activities in 1978 developing projects mainly on rendering and animation. Along the years, as new researchers joined the group, new research fields such as image acquisition and analy...

Since immersive VR devices have become commodities, immersive environments appear as a new tool in the development of high-fidelity prototypes of systems in which the user interaction relies on expensive or unusual hardware, e.g., industrial systems. However, there is not enough evidence that the interface of a complex system and its VR counterpart...

In electrical engineering, hardware experts often need to analyze electromagnetic radiation data to detect any external interference or anomaly. The field that studies this sort of assessment is called electromagnetic compatibility (EMC). As a way to support EMC analysis, we propose the use of Augmented Situated Visualization (ASV) to supply profes...

Whenever accessing indoor spaces such as classrooms or auditoriums , people might attempt to analyze and choose an appropriate place to stay while attending an event. Several criteria may be accounted for, and most are not always self-evident or trivial. This work proposes the use of data visualization allied to an Augmented Reality (AR) user inter...

In the context of promoting empathy among people without disabilities, we propose an application to allow users to experience having an amputated arm. By providing both visual and haptic feedback, our application offers a multisensory experience to enhance the sense of embodiment. The user of our application should still feel their real limb attach...

In EMC testing, 3D electromagnetic field data often needs to be visually analysed by an expert in order to detect product defects or unwanted interference between multiple devices. In this sense, the present work proposes the use of data visualization techniques allied to an Augmented Reality user interface to provide information that helps profess...

This paper summarizes our study of tactile languages in humancomputer interaction. We intended to analyze how the choices made during the design process of tactile vocabularies would affect the user performance on an interactive task. Therefore, we have developed and tested different sets of tactile signals for aid navigation in virtual environment...

Tangible objects are used in Virtual Reality (VR) and Augmented Reality (AR) to enhance haptic information on the general shape of virtual objects. However, they are often passive or unable to simulate rich varying mechanical properties. This paper studies the effect of combining simple passive tangible objects and wearable haptics for improving th...

The present work proposes the use of data visualization techniques allied to an Augmented Reality (AR) user interface to provide information for users to define the most convenient location to sit down at an event. This accounts for different sets of arbitrary demands by projecting 3D information directly atop the seats. The users can also rearrang...

Motor imagery Brain-Computer Interface (MI-BCI) enables bodyless communication by means of the imagination of body movements. Since its apparition , MI-BCI has been widely used in applications such as guiding a robotic prosthesis, or the navigation in games and virtual reality (VR) environments. Although psychological experiments, such as the Rubbe...

The present work proposes the use of data visu-alization techniques allied to an Augmented Reality (AR) user interface to provide information for users to define the most convenient location to sit down at an event. This accounts for different sets of arbitrary demands by projecting 3D information directly atop the seats. The users can also rearran...

When traveling, a very common issue is to ask for the help of a stranger to take a photo on a touristic spot. Indeed, often the results of this short collaboration are not as previously imagined. In this paper, we introduce the concept of instant rephotography, a technique based on a simple and intuitive user interface, and in an efficient and low...

Motor imagery Brain-Computer Interface (MI-BCI) is a paradigm widely used for controlling external devices by imagining bodily movements. This technology has inspired researchers to use it in several applications such as robotic prostheses, games, and virtual reality (VR) scenarios. We study the inclusion of an imaginary third arm as a part of the...

Sketching was traditionally a 2D task. Even when the new generation of VR devices allowed to sketch in 3D, the drawn models remained essentially static representations. In this paper, we introduce a new physics-inspired sketching technique built on the top of Position-based Dynamics to enrich the 3D drawings with dynamic behaviors. A particle-based...

Navigation in real environments is arguably one of the primary applications for the mixed reality (MR) interaction paradigm. We propose a wearable MR system based on off-the-shelf devices as an alternative to the widespread handheld-based GPS navigation paradigm. Our system uses virtual holograms placed on the terrain instead of the usual heads-up...

We present an assessment of asymmetric interactions in Collabora-tive Virtual Environments (CVEs). In our asymmetric setup, two co-located users interact with virtual 3D objects, one in immersive Virtual Reality (VR) and the other in mobile Augmented Reality (AR). We conducted a study with 36 participants to evaluate performance and collaboration a...

The visual fidelity of realistic renderings in Computer Graphics depends fundamentally upon how we model the appearance of objects resulting from the interaction between light and matter reaching the eye. In this paper, we survey the research addressing appearance modelling of living human tissue. Among the many classes of natural materials already...

The effectiveness of Virtual Environments (VEs) may be defined in terms of different aspects. A common one is the degree to which the VE creates in the user the subjective illusion of presence, the sense of being in the VE. Since presence is a subjective condition, it has most commonly been measured by subjective methods, especially by post-questio...

The effectiveness of Virtual Environments (VEs) may be defined in terms of different aspects. A common one is the degree to which the VE creates in the user the subjective illusion of presence, the sense of being in the VE. Since presence is a subjective condition, it has most commonly been measured by subjective methods, especially by post-questio...

In teleoperation, and particularly when controlling semi-autonomous robots that need to be supervised during long tasks, the user can be easily distracted losing its situational awareness. In this paper, we compare three types of alert signals: haptic, visual and auditory, to determine whats the better way to get the pre-attention of the user in cr...

In the context of the 3DUI Contest promoted by the IEEE VR 2018, we propose 3D interaction techniques that address three distinct tasks in a virtual environment setup: climbing a ladder, controlling a quadcopter in a first-person view flight, and building a tower by stacking a series of objects. The interaction techniques were developed so the play...

Phase-change phenomena are present in our daily life. Examples are the evaporation of a fluid when it reaches its boiling temperature, the condensation of water vapor in air due to the pressure changes or due to the difference of temperature in boundaries, and the melting of snow when winter is ending. Current development in physics-based animation...

Veering is a common experience for blind pedestrians and for individuals walking in unfamiliar spaces. In this paper, we assess a vibrotactile Head-Mounted Display to assist blind individuals to walk straight from a point to another. Our goal was to assess such device for both assistance and self-Orientation and Mobility (O&M) training to provide m...

In computer-mediated tactile intercommunication, users not only have to perceive tactile cues but also have to articulate them to carry a two-way interaction. By pressing buttons or performing specific gestures, interlocutors can exchange tactile signals but are not able to extrapolate the given vocabulary. When more access to hardware parameters i...

We present the design of a handheld-based interface for collaborative manipulations of 3D objects in mobile augmented reality. Our approach combines touch gestures and device movements for fast and precise control of 7-DOF transformations. Moreover, the interface creates a shared medium where several users can interact through their point-of-view a...

Introduction Mobile devices and software are now available with sufficient computing power, speed and complexity to allow for real-time interpretation of radiology exams. In this paper, we perform a multivariable user study that investigates concordance of image-based diagnoses provided using mobile devices on the one hand and conventional workstat...

In radiology diagnosis, medical images are most often visualized slice by slice. At the same time, the visualization based on 3D volumetric rendering of the data is considered useful and has increased its field of application. In this work, we present a case-based study with 16 medical specialists to assess the diagnostic effectiveness of a Virtual...

Object manipulation in 3D virtual environments demands a combined coordination of rotations, translations and scales, as well as the camera control to change the user's viewpoint. Then, for many manipulation tasks, it would be advantageous to share the interaction complexity among team members. In this paper we propose a novel 3D manipulation inter...

Simulations of cuts on deformable bodies have been an active research subject for more than two decades. However, previous works based on finite element methods and mass spring meshes cannot scale to complex surgical scenarios. This article presents a novel method that uses position-based dynamics (PBD) for mesh-free cutting simulation. The propose...

Due to the perceptual characteristics of the head, vibrotactile Head-mounted Displays are built with low actuator density. Therefore, vibrotactile guidance is mostly assessed by pointing towards objects in the azimuthal plane. When it comes to multisensory interaction in 3D environments, it is also important to convey information about objects in t...

Introduction A medical application running outside the workstation environment has to deal with several constraints, such as reduced available memory and low network bandwidth. The aim of this paper is to present an approach to optimize the data flow for fast image transfer and visualization on mobile devices and remote stationary devices. Methods...

Interaction in augmented reality environments may be very complex, depending on the degrees of freedom (DOFs) required for the task. In this work we present a 3D user interface for collaborative manipulation of virtual objects in augmented reality (AR) environments. It maps position - acquired with a camera and fiducial markers - and touchscreen in...

In radiology diagnosis, medical images are most often visualized slice by slice. At the same time, the visualization based on 3D volumetric rendering of the data is considered useful and has increased its field of application. In this work, we present a case-based study with 16 medical specialists to assess the diagnostic effectiveness of a Virtual...

With interactive maps a person can manage to find the way from one point to another, using an allocentric perspective (e.g. Google Maps), but also looking at a location as from the inside of the map with an egocentric perspective (e.g. Google Street View). Such experience cannot be performed with tactile maps, mostly explored from a top-view. To so...

In the radiology diagnosis process, medical images are most often visualized slice by slice on 2D screens or printed. At the same time, the visualization based on 3D volumetric rendering of the data is considered useful and has increased its field of application. In this work we present a user study with medical specialists to assess the diagnostic...

While improved visual realism is known to enhance training effectiveness in virtual surgery simulators, the advances on realistic rendering for these simulators is slower than similar simulations for man-made scenes. One of the main reasons for this is that in vivo data is hard to gather and process. In this paper, we propose the analysis of videol...

Computer simulation of surgical environments is always oversimplified in terms of physical behavior due to the complexity of the tissues and interactions involved, which cannot be fully simulated in real time. To better manage this trade-off between efficiency and effectiveness, we present a hybrid and adaptive environment that combines a set of me...

Aplicações médicas como simuladores virtuais de cirurgia são importantes ferramentas de estudo e treinamento para a área médica. A qualidade visual das cenas virtuais beneficia o desenvolvimento de habilidades pertinentes, de acordo com o conceito de simulação PSVR (\textit{Patient Specific Virtual Reality}). Neste contexto, técnicas de representaç...

Actuator density is an important parameter in the design of vibrotactile displays. When it comes to obstacle detection or navigation tasks, a high number of tactors may provide more information, but not necessarily better performance. Depending on the body site and vibration parameters adopted, high density can make it harder to detect tactors in a...

Every year there’s more than 700,000 work accidents in Brazil. To address their consequences, governments and companies spend more than 30 billion dollars a year. To reduce these accidents, we propose the use of VR simulators to assess capability for safe behavior among workers. In a typical simulation session, the user wears a head-mounted display...

In diagnosis, 3D image acquisition is ubiquitous (e.g. CT and MRI). Nevertheless, the outgoing images are most often visualized slice by slice on 2D screens or printed out. In some specific cases, however, it is useful to visualize a 3D volumetric rendering of the data. This is done as interactive projections on 2D conventional monitors, and allows...

Researchers have investigated the tracking and recognition of human postures for a long time. Firstly, with the objective of better understanding our movements and behaviors, and then to detect wrong movements and try to help people to perform better. The equipments used to track these movements were invasive, complex and expensive, but with the re...

Even if the sense of touch is fundamental in real life, few technology has implemented it efficiently in virtual reality. One of the reasons for that is the lack of knowledge on related technologies and on tactile perception. In this tutorial, we present the tools for building haptic interfaces for virtual applications. We start presenting the perc...

Several studies evaluated vibrotactile stimuli on the head to aid orientation and communication. However, the acuity for vibration of the head's skin still needs to be explored. In this paper, we report the assessment of the spatial resolution on the head. We performed a 2AFC psychophysical experiment systematically varying the distance between pai...