基于图像的虚拟现实技术在驾驶模拟器中的应用

近年来基于图像的虚拟现实技术发展迅速,它很好弥补了基于图形的三维虚拟场景构建方式中的不足。基于图像的虚拟现实技术主要包括基于图像的建模和漫游技术,本文将基于图像的漫游技术应用于汽车驾驶模拟器的视景系统,实现了一定区域内逼真的场景漫游。本文首先利用图像拼接技术实现单视点宽角度漫游,再通过图像插值和视图变形技术实现连续的多视点漫游。     

基于三角形对应关系的Morphing技术

基于图象生成的真实感图象有着不依赖于场景复杂度的突出优势。文中提出了一种基于三角形特征对应的Ｍｏｒｐｈｉｎｇ方法，它对局部信息进行综合，可以获得比传统的基于线段特征方法更快的处理速度，同时不会由于全局信息的影响而造成图象的扭曲失真     

全自动实时人脸图像变形技术研究与实现

提出了一种新的人脸图像变形方法——自适应网格方法(AMM)。该方法可以全自动产生实时的人脸变形效果。ASM(主动形状模型)技术的使用消除了其他人脸变形算法中所必须的手工标定人脸关键点工作；提出一种将人脸矩形区域自动划分成数个特征矩形的方法，使得复杂的图像变形计算被化简为简单高效的图像插值计算。该工作有助于将人脸变形技术运用于桌面实时应用中。     

一种多幅图像间的渐变技术

提出了一种图像渐变的新方法，即基于连分式插值Morphing技术。用此方法可以实现多幅不同图像之间的渐变。它是一新的非线性插值算法，与其他算法相比，该方法具有计算精度高、图像过渡平滑、易于编程实现等优点。更重要的是，它还具有信息隐藏的功能。     

Polyhedral Objects Metamorphosis Using Convex Decomposition and Morphology

A new technique is presented for computing continuous shape transformations between polyhedral objects. The polyhedron shape transformations can be divided into polyhedron metamorphosis and bi-directional local rigid body rotation transformation. By decomposing two objects into sets of individual convex sub-objects respectively, and establishing the matching between two subsets, the approach can solve the metamorphosis problem of two non-homotopic objects (including concave objects and holey objects). Compared with other methods, this metamorphosis algorithm can be executed automatically for arbitrary polyhedrons and no need user interaction. The user has the ability to choose an automatic matching or to select interactively pairs of corresponding matching convex subsets to obtain special effects. Experiments show that this method can generate natural, high-fidelity, eye-pleasing metamorphosis results with simple computation.     

3D shape metamorphosis based on T-spline level sets

We propose a new method for 3D shape metamorphosis, where the in-between objects are constructed by using T-spline scalar functions. The use of T-spline level sets offers several advantages: First, it is convenient to handle complex topology changes without the need of model parameterization. Second, the constructed objects are smooth (C² in our case). Third, high quality meshes can be easily obtained by using the marching triangulation method. Fourth, the distribution of the degrees of freedom can be adapted to the geometry of the object. Given one source object and one target object, we firstly find a global coordinate transformation to approximately align the two objects. The T-spline control grid is adaptively generated according to the geometry of the aligned objects, and the initial T-spline level set is found by approximating the signed distance function of the source object. Then we use an evolution process, which is governed by a combination of the signed distance function of the target object and a curvature-dependent speed function, to deform the T-spline level set until it converges to the target shape. Additional intermediate objects are inserted at the beginning/end of the sequence of generated T-spline level sets, by gradually projecting the source/target object to the initial/final T-spline level set. A fully automatic algorithm is developed for the above procedures. Experimental results are presented to demonstrate the effectiveness of our method.     

Developing future hourly weather files for studying the impact of climate change on building energy performance in Hong Kong

The concern on climate change leads to growing demand for minimization of energy use. As building is one of the largest energy consuming sectors, it is essential to study the impact of climate change on building energy performance. In this regard, building energy simulation software is a useful tool. A set of appropriate typical weather files is one of the key factors towards successful building energy simulation. This paper reports the work of developing a set of weather data files for subtropical Hong Kong, taking into the effect of future climate change. Projected monthly mean climate changes from a selected General Circulation Model for three future periods under two emission scenarios were integrated into an existing typical meteorological year weather file by a morphing method. Through this work, six sets of future weather files for subtropical Hong Kong were produced. A typical office building and a residential flat were modeled using building simulation program EnergyPlus. Hourly building energy simulations were carried out. The simulated results indicate that there will be substantial increase in A/C energy consumption under the impact of future climate change, ranging from 2.6% to 14.3% and from 3.7% to 24% for office building and residential flat, respectively.     

Efficient collision detection for models deformed by morphing

Published online: 5 February 2003     

Parametric dependence of a morphing wind turbine blade on material elasticity

A few recent works have suggested a morphing blade for wind turbine energy conversion. The concept is derived from fin and wing motions that better adapt to varying load conditions. Previous research has provided the fluid mechanic justification of this new concept. This paper establishes a parametric relationship between an asymmetric wind turbine blade and constituent material modulus to predict the geometric response of the morphing blade for a given material characteristic. The airfoil’s trailing edge deflection is associated to a prescribed fluid exit angle via the Moment Area (MA) method. Subsequently, a mathematical model is derived to predict material deformation with respect to imparted aerodynamic forces. Results show that an airfoil, much like a tapered beam, can be modeled as a non-prismatic cantilevered beam using this well established method.     

Self-intersection elimination in metamorphosis of two-dimensional curves

H :[0, 1]× ³→ ³, where H(t, r) for t=0 and t=1 are two given planar curves C ₁(r) and C ₂(r). The first t parameter defines the time of fixing the intermediate metamorphosis curve. The locus of H(t, r) coincides with the ruled surface between C ₁(r) and C ₂(r), but each isoparametric curve of H(t, r) is self-intersection free. The second algorithm suits morphing operations of planar curves. First, it constructs the best correspondence of the relative parameterizations of the initial and final curves. Then it eliminates the remaining self-intersections and flips back the domains that self-intersect.