图像局部纹理特性的静电力触觉渲染

目的 触摸触觉设备感知物体时,需要实现视觉-力触觉同步反馈,其中图像-力触觉反馈难点在于再现更真实的纹理触感的触觉渲染过程。本文提出了一种基于图像局部纹理特征的静电力触觉渲染模型,实现了更加清晰、触感真实的图像纹理的静电力触觉反馈。方法 首先,采用局部傅里叶变换方法强化局部纹理特征,提取傅里叶变换系数分离出表征形状和局部纹理、边缘的频域分量。其次,对局部纹理特征进行力触觉渲染,建立局部纹理特征与驱动信号的映射模型,采用比例模型将局部纹理特征值转化为同等级的静电力表达。最后,根据静电力与驱动信号的心理学模型,由局部纹理特征控制不同驱动信号的输出产生静电力触觉。结果 进行纹理触觉对比感知实验验证算法有效性,62.5%的实验参与者偏爱基于图像局部纹理的触觉渲染算法反馈的纹理触感,本文算法可以模拟多种图像的纹理、边缘的触感。结论 算法在频域分离图像局部纹理、边缘和形状特征,建立纹理-力触觉渲染模型,针对大多数图片可以有效地增强纹理触感,提升触觉再现交互技术的沉浸感。     

Electrostatic tactile display with thin film slider and its application to tactile telepresentation systems

A new electrostatic tactile display is proposed to realize compact tactile display devices that can be incorporated with virtual reality systems. The tactile display of this study consists of a thin conductive film slider with stator electrodes that excite electrostatic forces. Users of the device experience tactile texture sensations by moving the slider with their fingers. The display operates by applying two-phase cyclic voltage patterns to the electrodes. The display is incorporated into a tactile telepresentation system to realize explorations of remote surface textures with real-time tactile feedback. In the system, a PVDF tactile sensor and a DSP controller automatically generate voltage patterns to present surface texture sensations through the tactile display. A sensor, in synchronization with finger motion on the tactile display, scans a texture sample and outputs information about the sample surface. The information is processed by a DSP and fed back to the tactile display in real time. The tactile telepresentation system was evaluated in texture discrimination tests and demonstrated a 79 percent correct answer ratio. A transparent electrostatic tactile display is also reported in which the tactile display is combined with an LCD to realize a visual-tactile integrated display system.     

Vibratory tactile display of image-based textures

Virtual worlds must integrate tactile and force sensations to create a sense of presence. Our tactile display conveys the textural sensation of object surfaces to a user's fingertip. This vibratory tactile display contains a contact pin array that transmits vibrations to the human skin. This type of device has been investigated as a reading aid for the blind since the 1960s. A device called the Optacon, developed by J.G. Linvill and J.C. Bliss (1966) was intended for use by a visually impaired person. Therefore, methods for representing texture have not been discussed extensively for that device. We present techniques for virtually replicating surface texture sensations through a vibratory tactile display, using image data of objects. M. Minsky et al. (1990) demonstrated a method for presenting surface textures by force display, including-if needed-visual images of textures. Their system generated the images from geometrical shapes of depth maps. In contrast, we use pictures of real object surfaces to provide the distribution data for tactile stimulus     

振动触觉纹理再现技术研究综述

纹理力触觉再现是通过特定的硬件装置模拟产生与物体纹理表面接触时的触感，使用户能感受到物体的粗糙度、软硬度等纹理特征信息。振动刺激作为再现物体触觉信息的一种刺激方式，在纹理触觉再现中被广泛运用，产生了不同的振动触觉表达装置和纹理触觉表达方法。从纹理触觉认知的角度，阐述了人对振动刺激的触觉感知生理学基础；介绍了纹理触觉再现的原理和方法；从振动与纹理特征的映射方法以及振动刺激方式两个方面分析了目前振动触觉纹理再现技术的发展现状；最后对相关研究的发展进行了总结展望。     

虚平面映射:深度图像内部视点的绘制技术

首先推导与归纳了图像三维变换中像素深度场的变换规律,同时提出了基于深度场和极线原则的像素可见性别方法,根据上述理论和方法,提出一种基于深度图像的建模与绘制(image-based modeling and rendering,简称IBMR)技术,称为虚平面映射.该技术可以基于图像空间内任意视点对场景进行绘制.绘制时,先在场景中根据视线建立若干虚拟平面,将源深度图像中的像素转换到虚平面上,然后通过对虚平面上像素的中间变换,将虚平面转换成平面纹理,再利用虚平面的相互拼接,将视点的成像以平面纹理映射的方式完成.新方法还能在深度图像内侧,基于当前视点快速获得该视点的全景图,从而实现视点的实时漫游.新方法视点运动空间大、存储需求小,且可以发挥图形硬件的纹理映射功能,并能表现物体表面的三维凹凸细节和成像视差效果,克服了此前类似算法的局限和不足.     

宽幅度摩擦力控制触觉再现系统

触觉再现能够表达虚拟物体的表面特征,提高虚拟现实系统的真实感,因而成为人机交互领域内的研究重点。本文将空气压膜效应与电磁激励相结合,提出一种新颖的摩擦力控制触觉再现方法,并研制一种宽幅度摩擦力控制触觉再现系统,其中电磁激励用于增加摩擦力控制范围。经过一系列触觉感知实验验证了本系统的有效性,实验结果表明本文提出的方法相对于传统的摩擦力控制方法可以实现更宽泛的摩擦力系数控制。     

Haptic texture generation using stochastic models and teleoperation

In this paper, a method is suggested to generate haptic textures for isotropic surfaces using stochastic models. A Master-Slave tele-haptic system was realized by using two PHANToMs. Moving the stylus of the Master PHANToM by a user caused the Slave to scratch the surface of objects such as sandpaper or printing paper. Force data, generated by using the error between the Master and the Slave positions, were recorded and served as measures of the texture of the object in the remote environment. An estimate of haptic texture was obtained after a simple dynamic compensation of the force data. The haptic texture was modeled using a filter that was designed by analyzing the power-spectrum of estimated texture data. By passing White Gaussian Noise through the filter, virtual texture data could be generated. The forces corresponding to the virtual texture and the real texture by teleoperation were individually delivered through the Master PHANToM to users who were asked to identify or discriminate the corresponding textures. The users?? responses show that the virtual modeled textures were quite similar to the real ones.     

Generating haptic texture using solid noise

Texture enhances haptic interaction by providing unique, distinguishable, and versatile surfaces. In computer haptics, texture can render environments more realistic and provide useful information. In this paper, an algorithm is proposed for virtual texture simulation by using solid noise, where only a few parameters need to be altered to generate a range of realistic and diverse textures by reproducing different frequencies similar to that of real vibrational signals in a virtual environment. The proposed method can capture the textural effect in a haptic simulation while retaining a simple overall geometry and stable update rate. This method also allows the user to change the texture at runtime and can be easily incorporated into any existing code and used in any traditional haptic device without affecting overall haptic-rendering performance. Moreover, the solid noise texture is independent of object geometry and can be applied to any shape without additional computations. We conducted a human-subject study to evaluate the recognition accuracy for each generated haptic texture as well as its realism and correspondence to real texture. The results indicated the high performance of the method and its ability to generate haptic textures with a very high recognition rate that were highly realistic.     

Selectively stimulating skin receptors for tactile display

Research in virtual reality has recognized the need for more realistic tactile display in addition to touch and non-touch display and force display. We propose a method of selectively stimulating only superficial mechanoreceptors. We show that it makes people feel a more realistic, finer virtual texture than possible by adjusting the stimulator spacing. The apparatus is simple and we expect this idea to develop into a device to display varieties of tactile feeling     

面向视频感知的静电力触觉渲染方法

针对视觉障碍的人获取视频等数字媒体信息受限的问题, 为扩展视频等数字媒体信息的触觉感知通道,提出一种面向视频感知的静电力触觉渲染方法。首先,采用基于像素点的视频帧处理算法,根据手指触摸位置获取当前视频帧的目标像素点,然后将目标像素点彩色信息从RGB模型转换为HSI模型,利用像素点色调分量来映射静电力激励信号频率参量,结合像素点亮度和饱和度分量来映射静电力激励信号幅度参量,合成静电力触觉激励信号,实现对实时视频的触觉渲染和感知。最后,设计动态色彩感知实验和亮度辨识感知实验,结果表明,该方法可实现对视频中物体信息的触觉感知,动态识别平均正确率达90.6%,色彩辨识平均正确率达69.4%,亮度辨识平均正确率达80.0%,所提方法能有效提取视频中的动态特征信息,增强视频触觉渲染的实时性。     

基于图形硬件的纹理图像编码与实时绘制算法

真实感绘制对于细节的要求越来越高,应用程序通常采用多幅或大幅分辨率很高的纹理图像,有限的内存空间就成了一个制约的瓶颈.针对纹理图像的特点和可编程图形硬件的特殊要求,该文提出了一种新的面向绘制的编码算法--增量式纹理编码算法及相应的解压绘制算法,有效地解决了纹理存储容量和真实感之间的矛盾,并利用可编程图形硬件实现了实时解压绘制.该算法在图像压缩编码过程中,动态添加码表内容,只有当已有码表内容不能表示当前图像区域时,才增加码表内容.这种方法不仅能够对于自相似性较强的纹理图像取得很高的压缩比,而且由于码表的动态更新特性,可以对图像序列进行流式编码.在绘制纹理时,该算法充分利用了现有可编程图像硬件的特性,实现了实时解压绘制.文中分别对于静态图像和动态图像序列进行了实验,结果显示,此方法能灵活有效地对各类纹理图像进行编码.     

基于图像的室内虚拟环境的研究

基于图像的建模和绘制技术,提出了一个构造室内虚拟环境的完整方案,用户只需要输入少数照片,即可重建室内场景的全景图像,方案主要包括以下几点：首先由用户交互确定图像中的匹配象素,通过运动分析算法恢复整个场景的几何结构,然后,将原始图像变换至平面的参数坐标系,抽取纹理图像,并在参数空间对纹理图像进行拼接;最后生成场景的全景图像,算法对拍摄条件和设备没有苛刻要求,运算量较小,有较强的稳定性。     

Interactive virtual relighting of real scenes

Computer augmented reality (CAR) is a rapidly emerging field which enables users to mix real and virtual worlds. Our goal is to provide interactive tools to perform common illumination, i.e., light interactions between real and virtual objects, including shadows and relighting (real and virtual light source modification). In particular, we concentrate on virtually modifying real light source intensities and inserting virtual lights and objects into a real scene; such changes can be very useful for virtual lighting design and prototyping. To achieve this, we present a three-step method. We first reconstruct a simplified representation of real scene geometry using semiautomatic vision-based techniques. With the simplified geometry, and by adapting recent hierarchical radiosity algorithms, we construct an approximation of real scene light exchanges. We next perform a preprocessing step, based on the radiosity system, to create unoccluded illumination textures. These replace the original scene textures which contained real light effects such as shadows from real lights. This texture is then modulated by a ratio of the radiosity (which can be changed) over a display factor which corresponds to the radiosity for which occlusion has been ignored. Since our goal is to achieve a convincing relighting effect, rather than an accurate solution, we present a heuristic correction process which results in visually plausible renderings. Finally, we perform an interactive process to compute new illumination with modified real and virtual light intensities     

基于条块拼接的快速纹理合成

针对离线纹理合成算法所生成纹理占用较多存储空间的问题,提出一种所生成纹理可紧凑保存的快速纹理合成算法.该算法相继沿垂直和水平方向以条块拼接的方式合成纹理,合成结果可表示为一系列切割路径的组合,仅需保存这些切割路径即可在渲染时实时重建出纹理图像.通过在预处理中计算得到一组误差小的平行切割路径,合成时无需进行匹配,使得合成速度大幅提高.该算法对于在水平和垂直方向具有自相似性的纹理具有较高的合成质量.     

大规模地形场景三维实时漫游显示技术研究

地对大规模地形场景三维实时漫游显示中存在的技术问题，提出应用虚拟现有现实有关技术的思想，着重解决地形的多级分块表示、纹理多级贴图中数据结构组织的有关问题，最后用软件实现某一大场景地区的地形三维实时漫游显示。     

ANFIS modeling for predicting affective responses to tactile textures

The Adaptive Neuro‐Fuzzy Inference System (ANFIS) is proposed to simulate and analyze the mapping between the physical properties of tactile textures and people's affective responses. People were asked to rate the tactile feeling of 37 tactile textures against six pairs of adjectives on a semantic differential questionnaire. The friction coefficient, average roughness, compliance, and a thermal parameter of each tactile texture were measured. ANFIS models were built to predict the affective responses to tactile textures. The resulting ANFIS models demonstrated a good match between predicted and actual responses, and always yielded better performance when compared to linear and exponential regression models. The effects of physical properties of textures on affective responses were also analyzed by simulating the synthetic data with ANFIS. © 2011 Wiley Periodicals, Inc.     

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.     

虚拟飞行场景中事故特效的实时仿真

针对飞机的虚拟飞行仿真中,飞行事故仿真的真实感不强的问题,基于粒子系统, 结合动力学模型,实时渲染了爆炸、火焰、烟雾等飞行事故常见特效。使用四边形粒子代替传统 点粒子,结合纹理映射技术和融合技术,将真实感较强的纹理贴图与背景的帧缓存按照预设的融 合因子进行深度融合,提高了特效的真实感和实时性。通过粒子系统碰撞检测的方法,模拟烟雾 在飞机机舱内扩散,与舱壁发生碰撞的效果。搭建出模拟飞行的虚拟现实仿真系统,实现真实感 和沉浸感都很强的飞机爆炸、起火和冒烟等事故场景实时仿真。     

三维虚拟原子吸收实验室建模研究

本文提出了一种快速三维建模的方法,即用3DS MAX7．0来完成特殊物体的精确建模,用Outline3D 4．5来整合大场景,用Vrmlpad 2．1来进行后期加工、优化压缩与发布。以建立虚拟原子吸收实验室为例,研究了提高网络浏览速度的几个关键技术,如通过使用Billboard、Background节点、节约线面、优化压缩、降低纹理图分辨率等以优化文件;使用硬件渲染方式使虚拟场景显示快速、平滑。所完成的基于Web的三维虚拟原子吸收实验室场景形象逼真,可使用指定的浏览器插件来浏览,可从多视点观看,具有信息提示,活动门窗,自动漫游等功能和较好的交互性。     

Volumetric texture synthesis for non-photorealistic volume rendering of medical data

This paper presents a novel technique, called volumetric texture synthesis, for non-photorealistic volume rendering. It extends texture synthesis from 2D areas/3D surfaces to volumes. By selecting different texture samples, it allows for a wide variety of stylized rendering for the target volume. As a preprocessing step, volume data analysis is used to identify texture orientations for the volume. This is followed by volumetric texture synthesis, which generates 3D non-photorealistic textures along the identified texture orientations. Finally, standard volume rendering is applied to display the volume data decorated by the texture. Experimental results are provided in the paper.