 |
 |
|||||
 |
||||||
 |
||||||
|
prev
next
Download Free projecttopics From viewzoft
Project Overview
Our goal is to investigate issues in shape-based retrieval and analysis of 3D models. As a first step, we have developed a search engine for 3D polygonal models (check it out by clicking here). The main research issues are to develop effective shape representations and query interfaces. The Princeton Shape Benchmark is a set of 3D models that can be downloaded for further research. This web page provides an overview of some projects on these topics. Our publications provide more details.
--------------------------------------------------------------------------------
Shape Representations
A key issue in developing a shape-based retrieval and analysis system is to find a computational representation of shape (a shape descriptor) for which an index can be built, similarity queries can be answered efficiently. We are studying a spectrum of shape descriptors, ranging from ones that are simple to compute (but perhaps not very discriminating) to ones that require expensive computations (but provide sophisticated shape analysis):
Shape Distributions:
On the low end of the spectrum, we have been investigating shape distributions that represent the shape of a 3D model as a probability distribution sampled from a shape function measuring geometric properties of a 3D model. The motivation for this approach is that samples can be computed quickly and easily, and the shape of the resulting distributions are invariant to similarity transformations, noise, tessellation, cracks, etc.(with a normalization step for scale invariance). For example, one such shape distribution, which we call D2, represents the global shape of an object by the probability distribution of Euclidean distances between pairs of randomly selected points on its surface. The figure below shows the D2 distributions for 5 tanks (gray curves) and 6 cars (black curves). Note how the classes are distinguishable.
( MORE )
Download Free projecttopics From viewzoft
Overview:
Computer-aided acoustic modeling tools are important for design and simulation of three dimensional environments. For instance, an architect might use such a tool to evaluate the acoustic properties of a proposed auditorium design. Or, a factory designer might be able to predict the sound levels of any machine at any position on a factory floor. Acoustic modeling can also be used to provide sound cues to aid understanding, navigation, and communication in interactive virtual environment applications, particularly if acoustical simulations can be updated at interactive rates. For example, the voices of users sharing a virtual environment may be spatialized according to each users avatar location. The primary challenge in acoustic modeling is computation of reverberation paths from a sounds source position to a listeners receiving position. As sound may travel from source to receiver via a multitude of reflection, transmission, and diffraction paths, accurate simulation is extremely compute intensive. Prior approaches to acoustic simulation have used the image source method, whose computational complexity grows with O(n^r) (for n surfaces and r reflections), or ray tracing methods, which are prone to sampling error and require lots of computation to trace many rays. Due to the computational complexity of these methods, interactive acoustic simulation has generally been considered impractical. We have developed data structures and algorithms to enable interactive simulation of acoustic effects in large 3D virtual environments. Our approach is to precompute and store a spatial data structure that can be later used during an interactive session for evaluation of reverberation paths. The data structure is a beam tree that maps the convex pyramidal beam-shaped paths of significant transmission and specular reflection from a source point through 3D space. The beam tree is generated by: 1) partitioning 3D space into convex polyhedral regions, 2) computing the convex polygonal boundaries between regions, and 3) recursively splitting and tracing convex polyhedral beams from a source point through region boundaries (e.g., reflecting beams at opaque boundaries). The precomputed beam tree data structure can be used to compute specular reflection, transmission, and diffraction paths from a source position to any point in space at interactive rates. The lengths and directions of computed reveration paths may be used to spatialize audio source signals to a receiver moving under interactive control by a user. These data structures and algorithms have been integrated into a system for interactive acoustic modeling. The system takes as input: 1) a set of polygons describing the geometry and acoustic surface properties of the environment, and 2) a set of anechoic audio source signals at fixed locations. It outputs an audio signal auralized according to the computed delays, directions, and attenuations of the reverberation paths from each source to the receiver point. The receiver point can be moved interactively by the user, allowing real-time exploration of the acoustic environment ( MORE )
Download Free projecttopics From viewzoft
So far, lot of research has been performed in efficient querying of XML database systems -- XQuery being one of the most well-known query languages for XML. A wide range of commercial standards exist (XPath, DOM, etc. etc.) showing the widespread use of XML in industry.
In our XML project, we are currently developing an client/server based XML engine with the focus on updating XML data. The current engine is able to perform a wide range of XML updates in single user mode. The currently developed extensions to the system are an efficient index structure that is especially well suited for systems with high update rates, and the development of a concurrency control component taking advantage of the specific structure of XML documents. In our future work the system has to be extended in several important ways. The system requires an efficient buffer and storage management so that users can share data, and I/O management of the system is optimized. The system has to be extended by a reasonable query execution engine to provide a complete XML database management system. Knowledge needed: a general understanding of database systems, in particular buffer management, transactions, and query execution. Familiarity with processing semi-structured data. Some more information about our XML database management system. ( MORE )
prev next |
|
