High-fidelity, textured geometric models are a fundamental starting point for computergraphics, simulation, visualization, design, and analysis. Existing tools for acquiring 3D models of large-scale (e.g., urban) geo...
High-fidelity, textured geometric models are a fundamental starting point for computergraphics, simulation, visualization, design, and analysis. Existing tools for acquiring 3D models of large-scale (e.g., urban) geometry from imagery require significant manual input and suffer other, algorithmic scaling limitations. We are pursuing a research and engineering effort to develop a novel sensor, and associated geometric algorithms, to achieve fully automated reconstruction from close-range color images of textured geometric models representing built urban structures. The sensor is a geo-located camera, which annotates each acquired digital image with metadata recording the date and time of image acquisition, and estimating the position and orientation of the acquiring camera in a global (geodetic) coordinate system. This metadata enables the formulation of reconstruction algorithms which scale well both with the number and spatial density of input images, and the complexity of the reconstructed model. We describe an initial dataset of about four thousand geo-located images acquired through a prototype sensor, manual surveying, and semi-automated refinement of navigation information. We demonstrate, for a small office park on the MIT campus, the operation of fully automated algorithms for generating hemispherical image mosaics, for reconstructing vertical building facades, and for estimating high-resolution texture information for each facade. Finally, we describe the status of our efforts, and discuss several significant research and engineering challenges facing the project.
This paper describes how to compute the line or lines which intersect four given lines in three dimensions. This intersection computation arises in computergraphics (for visibility computations), computational geomet...
This paper describes how to compute the line or lines which intersect four given lines in three dimensions. This intersection computation arises in computergraphics (for visibility computations), computational geometry (for line traversals), and computer vision (for object recognition).
Perspective distortion, occlusion and specular reflection are challenging problems in shape-from-stereo. In this paper we review one recently published area-based stereo matching algorithm (Bhat and Nayar, 1998) desig...
详细信息
Perspective distortion, occlusion and specular reflection are challenging problems in shape-from-stereo. In this paper we review one recently published area-based stereo matching algorithm (Bhat and Nayar, 1998) designed to be robust in these cases. Although the algorithm is an important contribution to stereo-matching, we show that its coefficient has a low discriminatory power, which leads to a significant number of multiple best matches. In order to cope with this drawback we introduce a new normalized ordinal correlation coefficient. Experiments showing the behavior of the proposed coefficient are performed on various datasets including real data with ground truth. The new coefficient reduces the occurrence of multiple best matches to almost zero per cent. It also shows a more robust and equally accurate behavior. These benefits are achieved at almost no additional computational costs.
The Virtual Table presents stereoscopic graphics to a user in a workbench-like setting. For this device, a user interface and new interaction techniques have been developed based on transparent props a tracked hand-he...
详细信息
Synthetic modeling of human bodies and the simulation of motion is a long-standing problem in animation and much work is involved before a near-realistic performance can be achieved. At present, it takes an experience...
详细信息
Synthetic modeling of human bodies and the simulation of motion is a long-standing problem in animation and much work is involved before a near-realistic performance can be achieved. At present, it takes an experienced designer a very long time to build a complete and realistic model that closely resembles a specific person. Our ultimate goal is to automate the process and to produce realistic animation models given a set of video sequences. In this paper we show that, given video sequences of a person moving in front of the camera, we can recover shape information and joint locations. Both of which are essential to instantiate a complete and realistic model that closely resembles a specific person and without knowledge about the position of the articulations a character cannot be animated. This is achieved with minimal human intervention. The recovered shape and motion parameters can be used to reconstruct the original movement or to allow other animation models to mimic the subject's actions.
The paper proposes virtual input devices based on collision detection for easy construction of interactive 3D graphics applications which use a motion capture system as a real time input device. Each virtual input dev...
详细信息
The paper proposes virtual input devices based on collision detection for easy construction of interactive 3D graphics applications which use a motion capture system as a real time input device. Each virtual input device is composed from several collision sensor objects and an actuator object. These objects are software components represented as a visible object which users can manipulate on a computer screen. Each virtual input device has a certain metaphor associated with its role that is determined by location and composition structure of its components. Therefore, it is possible to define various virtual input devices easily only by combining several sensor objects and an actuator object through direct manipulations on a computer screen. The paper presents a realization mechanism and actual examples of virtual input devices.
This paper describes an algorithm for generating unstructured triangulations for arbitrarily shaped two-dimensional regions. The algorithm works for regions without cracks, as well as for regions with one or multiple ...
详细信息
This paper describes an algorithm for generating unstructured triangulations for arbitrarily shaped two-dimensional regions. The algorithm works for regions without cracks, as well as for regions with one or multiple cracks. The algorithm incorporates aspects of well-known meshing procedures and includes some original steps. It includes an advancing front technique, which uses a quadtree procedure to develop local guidelines for the size of generated elements. The advancing front technique is based on a standard procedure found in the literature, to improve mesh quality (as far as element shape is concerned), an a posteriori local mesh improvement procedure is used.
In this paper, a distributed computational system for finite element structural analysis and some strategies for improving its efficiency are described. The system consists of a set of programs that performs the struc...
详细信息
Endonasal sinus surgery requires a great amount of training before it can be adequately performed. The complicated anatomy involved, the proximity of relevant structures, and the variability of the anatomy due to inbo...
详细信息
暂无评论