Six degree-of-freedom haptic rendering using spatialized normal cone search

This paper describes a haptic rendering algorithm for arbitrary polygonal models using a six degree-of-freedom haptic interface. The algorithm supports activities such as virtual prototyping of complex polygonal models and adding haptic interaction to virtual environments. The underlying collision system computes local extrema in distance between the model controlled by the haptic device and the rest of the scene. The haptic rendering computes forces and torques on the moving model based on these local extrema. The system is demonstrated on models with tens of thousands of triangles and developed in an accessibility application for finding collision-free paths.     

Stable adaptive algorithm for Six Degrees-of-Freedom haptic rendering in a dynamic environment

Recently, physically-based simulations with haptics interaction attracted many researchers. In this paper, we propose an adaptive Six Degrees-of-Freedom (6-DOF) haptic rendering algorithm based on virtual coupling, which can automatically adjust virtual coupling parameters according to mass values of the simulated virtual tools. The algorithm can overcome the virtual tool displacement problem caused by the large mass values of the virtual tool and can provide stable force/torque display. The force/torque magnitude is saturated to the maximum force/torque values of the haptic device automatically. The implemented algorithm is tested on the simple and complex standard benchmarks. The experimental results confirm that the proposed adaptive 6-DOF haptic rendering algorithm displays good stability and accuracy for haptic rendering of dynamic virtual objects with mass values.     

虚拟体空间中的触觉雕刻

目前，在虚拟环境中大多数的信息获取是通过视觉、听觉等非接触感觉获得的。然而缺乏触觉反馈的信息减少了很大一部分的信息源。在看和听之外，能够触摸、感觉和操纵物体，在很大程度上提高了虚拟环境的真实性。该文研究了触觉绘制的基本模型，提出了采用虚平面作为中介实现体数据的实时触觉绘制。并在此基础上探讨了体的局部变形及结合触觉反馈模型，实现了具有触觉反馈的虚拟雕刻交互系统。该系统可应用于融化、燃烧、印记、构造和着色实时交互操作。     

A Precomputed Approach for Real-Time Haptic Interaction with Fluids

The key to enhancing perception of the virtual world is improving mechanisms for interacting with that world. Through providing a sense of touch, haptic rendering is one such mechanism. Many methods efficiently display force between rigid objects, but to achieve a truly realistic virtual environment, haptic interaction with fluids is also essential. In the field of computational fluid dynamics, researchers have developed methods to numerically estimate the resistance due to fluids by solving complex partial differential equations, called the Navier-Stokes equations. However, their estimation techniques, although numerically accurate, are prohibitively time-consuming. This becomes a serious problem for haptic rendering, which requires a high frame rate. To address this issue, we developed a method for rapidly estimating and displaying forces acting on a rigid virtual object due to water. In this article, we provide an overview of our method together with its implementation and two applications: a lure-fishing simulator and a virtual canoe simulator     

Touch-enabled haptic modeling of deformable multi-resolution surfaces

Currently, interactive data exploration in virtual environments is mainly focused on vision-based and non-contact sensory channels such as visual/auditory displays. The lack of tactile sensation in virtual environments removes an important source of information to be delivered to the users. In this paper, we propose the touch-enabled haptic modeling of deformable multi-resolution surfaces in real time. The 6-DOF haptic manipulation is based on a dynamic model of Loop surfaces, where the dynamic parameters are computed easily without subdividing the control mesh recursively. A local deforming scheme is developed to approximate the solution of the dynamics equations, thus the order of the linear equations is reduced greatly. During each of the haptic interaction loop, the contact point is traced and reflected to the rendering of updated graphics and haptics. The sense of touch against the deforming surface is calculated according to the surface properties and the damping-spring force profile. Our haptic system supports the dynamic modeling of deformable Loop surfaces intuitively through the touch-enabled interactive manipulation.     

A Survey of Haptic Rendering Techniques

Computer Graphics technologies have developed considerably over the past decades. Realistic virtual environments can be produced incorporating complex geometry for graphical objects and utilising hardware acceleration for per pixel effects. To enhance these environments, in terms of the immersive experience perceived by users, the human's sense of touch, or haptic system, can be exploited. To this end haptic feedback devices capable of exerting forces on the user are incorporated. The process of determining a reaction force for a given position of the haptic device is known as haptic rendering. For over a decade users have been able to interact with a virtual environment with a haptic device. This paper focuses on the haptic rendering algorithms which have been developed to compute forces as users manipulate the haptic device in the virtual environment.     

Toward realistic haptic rendering of surface textures

New sophisticated haptic-rendering algorithms let users experience virtual objects through touch. We systematically investigate the unrealistic behavior of virtual haptic textures. The emerging science of haptic rendering consists of delivering properties of physical objects through the sense of touch. Owing to the recent development of sophisticated haptic-rendering algorithms, users can now experience virtual objects through touch in many exciting applications, including surgical simulations, virtual prototyping, and data perceptualization. Haptics holds great promise to enrich the sensory attributes of virtual objects that these systems can produce. One area that has received increasing attention in the haptics community is haptic texture rendering, the goal of which is to introduce micro-geometry-scale features on object surfaces. Haptic objects rendered without textures usually feel smooth, and sometimes slippery. Appropriate haptic textures superimposed on haptic objects enhance an object's realism.     

用于实时柔性触觉再现的平行菱形链连接模型

精度高且实时性好的柔性触觉变形模型是实现触觉再现系统的关键。提出了一种新的基于物理意义的平行菱形链连接触觉变形模型,系统中各个链结构单元相对位移的叠加对外等效为物体表面的变形,与之相连的弹簧弹性力的合力等效为物体表面的接触力。使用Delta 6-DOF手控器,建立了触觉再现实验系统,对柔性体的接触变形和实时虚拟触觉反馈进行仿真, 实验结果表明所提出的模型不仅计算简单,而且能够保证触觉接触力和形变计算具有较高精度,满足虚拟现实系统对精细作业和实时性的要求。     

面向磁悬浮视触觉交互的多速率系统框架

非接触式磁悬浮视触觉交互克服了机械式交互的固有摩擦,具有广阔应用前景,但存在交互过程中虚拟工具穿透物体、图形渲染与触觉渲染速率不一致等问题.针对上述问题,提出面向磁悬浮视触觉交互的多速率系统框架,通过扩展三自由度(3-DOF)单射线触觉渲染方法,利用多射线对虚拟工具进行建模,避免工具穿透,实现六自由度(6-DOF)触觉...     

A haptic-rendering technique based on hybrid surface representation

A novel haptic rendering technique using a hybrid surface representation addresses conventional limitations in haptic displays. A haptic interface lets the user touch, explore, paint, and manipulate virtual 3D models in a natural way using a haptic display device. A haptic rendering algorithm must generate a force field to simulate the presence of these virtual objects and their surface properties (such as friction and texture), or to guide the user along a specific trajectory. We can roughly classify haptic rendering algorithms according to the surface representation they use: geometric haptic algorithms for surface data, and volumetric haptic algorithms based on volumetric data including implicit surface representation. Our algorithm is based on a hybrid surface representation - a combination of geometric (B-rep) and implicit (V-rep) surface representations for a given 3D object, which takes advantage of both surface representations.     

视触觉融合的增强现实三维注册方法

增强现实技术是近年来人机交互领域的研究热点。在增强现实环境下加入触觉感知,可使用户在真实场景中看到并感知到虚拟对象。为了实现增强现实环境下与虚拟对象之间更加自然的交互,提出一种视触觉融合的三维注册方法。基于图像视觉技术获得三维注册矩阵;借助空间转换关系求解出触觉空间与图像空间的转换关系;结合两者与摄像头空间的关系实现视触觉融合的增强现实交互场景。为验证该方法的有效性,设计了一个基于视触觉增强现实的组装机器人项目。用户可触摸并移动真实环境中的机器人零件,还能在触摸时感受到反馈力,使交互更具真实感。     

Haptic rendering: introductory concepts

Haptic rendering allows users to "feel" virtual objects in a simulated environment. We survey current haptic systems and discuss some basic haptic-rendering algorithms. In the past decade we've seen an enormous increase in interest in the science of haptics. Haptics broadly refers to touch interactions (physical contact) that occur for the purpose of perception or manipulation of objects. These interactions can be between a human hand and a real object; a robot end-effector and a real object; a human hand and a simulated object (via haptic interface devices); or a variety of combinations of human and machine interactions with real, remote, or virtual objects. Rendering refers to the process by which desired sensory stimuli are imposed on the user to convey information about a virtual haptic object.     

高度复杂拟凸体的实时触觉绘制

触觉绘制目前已成为虚拟现实的研究热点之一,其核心是触觉代理与目标物体的实时碰撞检测与距离计算,对高度复杂模型的触觉绘制仍然是虚拟现实领域的难题,原因是对模型复杂度敏感的算法均不能满足触觉绘制苛刻的时间要求.提出触觉包围盒概念,并针对拟凸体提出一种基于触觉包围盒的实时触觉绘制算法.触觉包围盒记录了离散的采样光线与目标物体的相交信息,进行触觉计算时,只需要执行1次线段与包围盒求交运算和5次双线性插值运算即可高速求出碰撞信息,且所得到的碰撞信息可直接用于反馈力计算.实验结果表明,该算法不仅快速有效,而且具有与触觉绘制模型复杂度不相关的优点.     

Real-time area-based haptic rendering and the augmented tactile display device for a palpation simulator

Although people usually contact a surface with some area rather than a point, most haptic devices allow a user to interact with a virtual object at one point at a time and likewise most haptic rendering algorithms deal with such situations only. In a palpation procedure, medical doctors push and rub the organ's surface, and are provided the sensation of distributed pressure and contact force (reflecting force) for discerning doubtable areas of the organ. In this paper, we suggest real-time area-based haptic rendering to describe distributed pressure and contact force simultaneously, and present a haptic interface system to generate surface properties in accordance with the haptic rendering algorithm. We represent the haptic model using the shape-retaining chain link (S-chain) framework for a fast and stable computation of the contact force and distributed pressure from a volumetric virtual object. In addition, we developed a compact pin-array-type tactile display unit and attached it to the PHANToM^TM haptic device to complement each other. For the evaluation, experiments were conducted with non-homogenous volumetric cubic objects consisting of approximately 500 000 volume elements. The experimental results show that compared to the point contact, the area contact provides the user with more precise perception of the shape and softness of the object's composition, and that our proposed system satisfies the real-time and realism constraints to be useful for a virtual reality application.     

Phantom-based haptic interaction with virtual objects

In 1993, haptic interaction with computers took a significant step forward with the development of the Phantom haptic interface. This simple device has spawned a new field analogous to computer graphics-computer haptics-defined as the discipline concerned with the techniques and processes associated with generating and displaying synthesized haptic stimuli to the human user. Inspired by the authors' previous work in interpreting robot touch sensor information and study of human touch perception, the Phantom interface permits users to feel the forces of interaction they would encounter while touching objects with the end of a stylus or the tip of their finger. The resulting sensations prove startling, and many first-time users are quite surprised at the compelling sense of physical presence they encounter when touching virtual objects. To appreciate why the Phantom system succeeded where others failed, you need to understand the nature and functioning of the human haptic system.     

Haptic rendering of rigid contacts using impulsive and penalty forces

A new simulation approach is proposed to improve the stability and the perceived rigidity of contacts during haptic interaction with multirigid body virtual environments. The approach computes impulsive forces upon contact and penalty and friction forces during contact. The impulsive forces are derived using a new multiple collision resolution method that never increases the kinetic energy of the system. When new contacts arise, the impulsive forces generate large hand accelerations without requiring increased contact stiffness and damping. Virtual objects and linkages are regarded as points in the configuration space, and no distinction is made between them in the proposed approach.     

Improving contact realism through event-based haptic feedback

Tapping on surfaces in a typical virtual environment feels like contact with soft foam rather than a hard object. The realism of such interactions can be dramatically improved by superimposing event-based, high-frequency transient forces over traditional position-based feedback. When scaled by impact velocity, hand-tuned pulses and decaying sinusoids produce haptic cues that resemble those experienced during real impacts. Our new method for generating appropriate transients inverts a dynamic model of the haptic device to determine the motor forces required to create prerecorded acceleration profiles at the user's fingertips. After development, the event-based haptic paradigm and the method of acceleration matching were evaluated in a carefully controlled user study. Sixteen individuals blindly tapped on nine virtual and three real samples, rating the degree to which each felt like real wood. Event-based feedback achieved significantly higher realism ratings than the traditional rendering method. The display of transient signals made virtual objects feel similar to a real sample of wood on a foam substrate, while position feedback alone received ratings similar to those of foam. This work provides an important new avenue for increasing the realism of contact in haptic interactions.     

Virtual prototyping of mechanical systems with tool mediated haptic feedback

Haptic feedback usually involves two types of stimulation forces: forces that address the touch sense and forces that address the kinesthetic perception. Touch forces have a low intensity and a complex structure since they reflect contact phenomena where friction plays an important role. Therefore, they are quite difficult to simulate. Virtual prototyping with haptic feedback should ideally involve both types of forces, but the integration of the touch feeling makes the simulator very complex. In this paper, we present a novel concept for virtual prototyping in which the touch interaction is separated from the kinesthetic force feedback. This is possible using a prototype that has a real part undertaking the touch interaction and a virtual part that simulate feedback for the kinesthetic forces. In this way, a full haptic interaction with the virtual prototype is established by means of a device that provides a realistic simulation of the product. In order to illustrate the concept, several experiments have been carried out for the case of specific subsystems of a car, which are particularly involved in the driver–car interaction: steering system, clutch pedal and the gearshift. A user test is described in the last part as well as the conclusions of the research.     

Biological cell injection visual and haptic interface

This paper presents a new three-dimensional (3-D) biomicromanipulation system for biological objects such as embryos, cells or oocytes. As the cell is very small, kept in liquid and observed through a microscope, 2-D visual feedback makes accurate manipulation in the 3-D world difficult. To improve the manipulation work, we proposed an intelligent human–machine interface. The 3-D visual information is provided to the operator through a 3-D reconstruction method using vision-based tracking deformations of the cell embryo. In order to perform stable microinjection tasks, the operator needs force feedback and haptic assistance during penetration of the cell envelop — the chorion. Thus, realistic haptic rendering techniques have been implemented to validate stable insertion of a micropipette in a living cell. The proposed human–machine user's interface allows real-time realistic visual and haptic control strategies for constrained motion in image coordinates, virtual haptic rendering to constrain the path of insertion and removal in the 3-D scene or to avoid cell destruction by adequately controlling position, velocity and force parameters. Experiments showed that the virtualized reality interface acts as a tool for total guidance and assistance during microinjection tasks.     

Improving virtual reality navigation tasks using a haptic vest and upper body tracking

Haptic feedback is an important component of immersive virtual reality (VR) applications that is often suggested to complement visual information through the sense of touch. This paper investigates the use of a haptic vest in navigation tasks. The haptic vest produces a repulsive vibrotactile feedback from nearby static virtual obstacles that augments the user spatial awareness. The tasks require the user to perform complex movements in a 3D cluttered virtual environment, like avoiding obstacles while walking backwards and pulling a virtual object. The experimental setup consists of a room-scale environment. Our approach is the first study where a haptic vest is tracked in real time using a motion capture device so that proximity-based haptic feedback can be conveyed according to the actual movement of the upper body of the user.User study experiments have been conducted with and without haptic feedback in virtual environments involving both normal and limited visibility conditions. A quantitative evaluation was carried out by measuring task completion time and error (collision) rate. Multiple haptic rendering techniques have also been tested. Results show that under limited visibility conditions proximity-based haptic feedback generated by a wearable haptic vest can significantly reduce the number of collisions with obstacles in the virtual environment.