从VRML到MultiGen/Vega的造型转换与简化—澳门大学虚拟漫游系统实践

复杂场景的虚拟漫游一直是虚拟现实和图形学领域一个非常重要的课题,它在城市规划、文化传播、旅游工业等领域有着极为广泛的应用前景.本文在原有系统的基础上,将VRML语言构造的整个澳门大学虚拟场景转换成MultiGen格式,并且在Vega上实现了对整个场景的实时漫游.与原有VRML语言所实现的虚拟场景相比较,新系统使得虚拟漫游更加灵活方便,且速度具有显著的提高.本文将论述格式转换中的若干技术问题.中国自动化学

example-based microfacet synthesis for appearance modeling of thin transparent materials

轻薄透明材质的折射现象在生活中很常见,为获得高质量的绘制效果,使用现有的表观建模方法需采集大量数据,为此提出一种数据处理的方法.使用照相机从一个固定角度对材质样本进行拍摄后,使用微平面合成方法为每一个表面点处的法向量分布函数(NDF)片段寻找与之形态相同而朝向不同的数据来补全当前NDF,得到具有较多细节的完整的双向传输分布函数.只需采集规模较小的数据,通过查找和补全处理即可获得完整数据.实验结果表明,文中方法简单易行,在增强绘制效果和细节的同时使得数据采集的效率得到提升.国家“九七三”重点基础研究发展计划项目(2009CB320802)|国家自然科学基金(60883007,60773030,60573155)|GrantofUniversityofMacauRefractions through thin transparent materials are common in everyday life. Massive data must be captured in order to obtain high quality rendering results with existing modeling methods. We present a new technique that adds additional processing to the captured data, and reduce capture task. We place a camera at a fixed position, and apply microfacet synthesis onto the captured dataset. For the partial normal distribution function (NDF) data at each surface point, we complete the NDF data with partial NDF with similar shapes but different orientations from other surface points. Once we have the complete NDF data, we compute the bidirectional transmission distribution function. Experimental results show the method permits both high quality rendering result and efficient data capture

3d human motion reconstruction from monocular videos through iterative optimization

提出并实现了一种从单目视频流中重建人体三维运动的方法.该方法通过交互定制得到个性化的人体骨架模型和视频序列每一帧中人体各关节点的二维坐标后,分别针对单帧和连续多帧进行优化并迭代求解,得到每一帧的比例因子的最优解;最后反求各关节点的三维坐标,重建人体三维运动序列.对包含复杂和快速多变的人体运动的视频进行的实验表明,该方法简单有效,适用于包括体育、影视等在内的实际视频源

一种基于物理的雨打树枝动态仿真方法

提出了一种应用物理学原理的树枝和雨滴交互作用的真实感动态仿真技术.树枝和叶柄被描述为一种方便由4种弹簧控制的三棱柱弹簧模型(extended three-prism spring model,简称ETPSM).树枝、树叶的运动源于树枝系统与雨滴相互之间能量的双向转换.二者之间的交互作用可以通过一种高效的技术很好地模拟.该技术被专门设计用来模拟液体在具有亲水性的非刚体表面上运动.当雨滴撞击树枝后,树枝会发生震动与转动;雨滴会沿着树叶表面流动,合并成一个更大的雨滴或者悬挂在叶片边缘;当雨滴从树叶边缘落下后,树枝会弹起并恢复到原来的位置.实验结果表明,该技术能够高效、真实地仿真雨滴撞击树枝系统后的相互作用效果,同时可以简单而有效地模拟杆状物体在外力作用下的弹性形变,诸如旋转、震动等.This paper presents an approach to animate realistic interactions between tree branches and raindrops, based on physical theory. Tree branches and petioles are represented by a model namely ETPSM (extended three-prism spring model) with three-prism structures, which can be flexibly controlled by four kinds of spring systems. The branches and leaves are animated due to the bidirectional transference of kinetic energy between raindrops and the branch system. The interactions between them can be well simulated by an efficient technique, specially designed for liquid motion on non-rigid objects with hydrophilic surfaces. When the branches are impacted by a raindrop, they will vibrate and twist, and the raindrops will flow along the leaf vein, merge into larger ones, or hang on the leaf apex, and the branch will rebound and vibrate for a while after the raindrop falls off the leaf, finally into a rest place. Experimental results show that this approach can be used to efficiently and realistically simulate these interactions between tree branches and raindrops; meanwhile, it can efficiently and easily simulate the elastic deformation of rod under the influence of external forces, such as rotation and vibration. © 2011 ISCAS

自适应三维美工树木骨架提取算法

中国计算机学会 中国自动化学会 中国图学学会 中国图象图形学学会 中国系统仿真学

combining multiple reference images in a backward mapping algorithm for novel view generation

提出了一种从多幅参考图像来合成新视点目标图像的逆映射算法.这种方法不但成功地填补了由于投影区域扩张而产生的第1类空洞,而且还成功地填补了由于空间非深度连续物体相互遮挡而产生的第2类空洞,从而方便地实现了虚拟环境中的漫游.基于物体表面深度的连续性,提出了一种位移预测方法.该方法可以从单幅参考图像获得逆映射过程中所需要的目标图像的位移信息,从而大大提高了算法的效率.与通常的正向映射算法相比,该算法克服了多幅参考图像所带来的计算量成倍增长等问题,而且误差较小

multiple-image-based modeling of trees

基于图象的造型技术(Image-based modeling)是目前计算机图形学的研究热点之一.与传统的基于几何的造型技术相比,基于图象的造型技术具有造型过程简单直观、真实感强等许多优点.本文基于计算机图形学、图象处理、图象变形以及计算机视觉领域的一些方法和技术,提出一种基于图象的树木造型方法.与传统的基于数学或生物学的树木造型方法不同,我们以图象为输入,通过人机交互、充分分析和利用图象信息,生成形态上与图象中的自然树木极为类似的几何模型.由于取材于真实的自然树木,造型具有很强的真实感.在重建过程的各各

simulation of physically-based tree animation in realtime

提出一种在GPU上实现基于力学运动原理的层次结构树木运动的并行仿真技术。该技术通过分析物理运动原理与多层次的矩阵结构(HMSM)算法的并行性,来达到将树木动画在图形硬件CUDA平台上进行加速的目的。首先介绍层次结构树木在外力诸如风力等作用下的物理运动原理;然后,针对树木的物理运动以及层次结构叠加算法详细地进行并行性分析;之后着重阐述CUDA框架下树木运动的并行结构设计过程与并行算法的详细设计方法;最后在GPU上执行树木物理运动仿真。实验结果表明,该技术不但能够生成真实感较强的树木动画序列,还能够实时模拟基于物理的树木运动。同时,该技术给计算机动画的加速算法提供了很好的思想。国家自然科学基金项目(60833007,60773030,60973066)|国家高技术研究发展计划(863)项目(2008AA01Z301)|澳门科研基金项目We propose an approach to automatically extracting foreground regions. This is a novel method for segmenting salient objects from still images by background elimination. To extract foreground regions, a new method of background elimination based on multiscale segmentation is proposed to detect candidate object regions. To this end, we use a trimap consisting of foreground, background, and undefined regions and a region adjacency graph. A graph-cut technique is finally used to extract exact foreground regions from the candidates. Experimental results have shown that the proposed method yields a better foreground extraction than Kim's method under various environments containing multiple objects and clutter backgrounds in natural images. © 2011 Society of Photo-Optical Instrumentation Engineers (SPIE)

gpu based real-time rendering of spherical depth image

提出了一种GPU加速的实时基于图像的绘制算法.该算法利用极坐标系生成对物体全方位均匀采样的球面深度图像;然后根据推导的两个预变换公式将单幅球面深度图像预变换到物体包围球的一个与视点相关的切平面上,以生成中间图像;再利用纹理映射生成最终目标图像.利用现代图形硬件的可编程性和并行性,将预变换移植到Vertex Shader来加快绘制速度;利用硬件的光栅化功能来完成图像的插值,以得到连续无洞的结果图像.此外,还在Pixel Shader上进行逐像素的光照以及环境映射的计算,生成高质量的光照效果.最终,文章解决了算法的视点受限问题,并设计了一种动态LOD(Level of Details)算法,实现了一个实时漫游系统,保持了物体间正确的遮挡关系

self-adapting algorithm of 3d art-designing tree skeleton extraction

提出了一种自适应三维美工树木骨架提取算法。该算法主要由前处理、骨架提取和后处理三个步骤组成。前处理阶段依次完成预计算操作,包括对具有几何相似性的子枝进行聚类,自适应生成每个子枝点云的聚类长度阈值,确定子枝之间的父子关系等;骨架提取阶段实现对每个子枝点云的聚类,及其对应骨架点、骨架曲线的生成等操作;后处理阶段完成孤立骨架节点去除,整棵树所有骨架曲线光滑化等处理。该树木骨架提取过程完全由计算机自动完成,不需要用户的任何干预。实验结果表明,采用该算法得到的美工树木骨架既能完整地保持树木模型的形状,又能正确地实现树木模型的拓扑结构。中央高校基本科研业务费专项资金(BLX2012049)|国家自然科学基金(60833007,60773030,60973066,61100132)|国家重点基础研究发展规划(973)(2009CB320802)|澳门大学研究基金To extract 3D art-designing tree skeleton, this paper proposes a self-adapting algorithm with three main steps: pre-processing, skeleton extraction and post-processing. The pre-processing sequentially implements the pre- computing operations such as clustering all the sub-branches of the same geometry similarity, self-adaptively generating clustering-length threshold for each sub-branch, determining parent-child relationships between sub-branches. The skeleton extraction processing introduces the approaches to cluster cloud points, generate corresponding skeleton-nodes and form skeleton curve using these skeleton nodes for each sub-branch. The post-processing deletes all the separate skeleton nodes and lines and smoothes skeleton curve for the whole tree. This approach is running on computer platform fully automatically, without any intervention of users. The experimental results indicate that the algorithm in this paper can generate smoothly skeleton curve, accompanied with the complete shape and the correct topology structure of tree model