1,046 research outputs found
3-D surface modelling of the human body and 3-D surface anthropometry
This thesis investigates three-dimensional (3-D) surface modelling of the human
body and 3-D surface anthropometry. These are two separate, but closely related, areas. 3-D surface modelling is an essential technology for representing and describing the surface
shape of an object on a computer. 3-D surface modelling of the human body has wide
applications in engineering design, work space simulation, the clothing industry, medicine,
biomechanics and animation. These applications require increasingly realistic surface
models of the human body. 3-D surface anthropometry is a new interdisciplinary subject. It
is defined in this thesis as the art, science, and technology of acquiring, modelling and
interrogating 3-D surface data of the human body. [Continues.
Advanced multilateration theory, software development, and data processing: The MICRODOT system
The process of geometric parameter estimation to accuracies of one centimeter, i.e., multilateration, is defined and applications are listed. A brief functional explanation of the theory is presented. Next, various multilateration systems are described in order of increasing system complexity. Expected systems accuracy is discussed from a general point of view and a summary of the errors is listed. An outline of the design of a software processing system for multilateration, called MICRODOT, is presented next. The links of this software, which can be used for multilateration data simulations or operational data reduction, are examined on an individual basis. Functional flow diagrams are presented to aid in understanding the software capability. MICRODOT capability is described with respect to vehicle configurations, interstation coordinate reduction, geophysical parameter estimation, and orbit determination. Numerical results obtained from MICRODOT via data simulations are displayed both for hypothetical and real world vehicle/station configurations such as used in the GEOS-3 Project. These simulations show the inherent power of the multilateration procedure
3D Fluid Flow Estimation with Integrated Particle Reconstruction
The standard approach to densely reconstruct the motion in a volume of fluid
is to inject high-contrast tracer particles and record their motion with
multiple high-speed cameras. Almost all existing work processes the acquired
multi-view video in two separate steps, utilizing either a pure Eulerian or
pure Lagrangian approach. Eulerian methods perform a voxel-based reconstruction
of particles per time step, followed by 3D motion estimation, with some form of
dense matching between the precomputed voxel grids from different time steps.
In this sequential procedure, the first step cannot use temporal consistency
considerations to support the reconstruction, while the second step has no
access to the original, high-resolution image data. Alternatively, Lagrangian
methods reconstruct an explicit, sparse set of particles and track the
individual particles over time. Physical constraints can only be incorporated
in a post-processing step when interpolating the particle tracks to a dense
motion field. We show, for the first time, how to jointly reconstruct both the
individual tracer particles and a dense 3D fluid motion field from the image
data, using an integrated energy minimization. Our hybrid Lagrangian/Eulerian
model reconstructs individual particles, and at the same time recovers a dense
3D motion field in the entire domain. Making particles explicit greatly reduces
the memory consumption and allows one to use the high-res input images for
matching. Whereas the dense motion field makes it possible to include physical
a-priori constraints and account for the incompressibility and viscosity of the
fluid. The method exhibits greatly (~70%) improved results over our recently
published baseline with two separate steps for 3D reconstruction and motion
estimation. Our results with only two time steps are comparable to those of
sota tracking-based methods that require much longer sequences.Comment: To appear in International Journal of Computer Vision (IJCV
Optimal Surface Fitting of Point Clouds Using Local Refinement
This open access book provides insights into the novel Locally Refined B-spline (LR B-spline) surface format, which is suited for representing terrain and seabed data in a compact way. It provides an alternative to the well know raster and triangulated surface representations. An LR B-spline surface has an overall smooth behavior and allows the modeling of local details with only a limited growth in data volume. In regions where many data points belong to the same smooth area, LR B-splines allow a very lean representation of the shape by locally adapting the resolution of the spline space to the size and local shape variations of the region. The iterative method can be modified to improve the accuracy in particular domains of a point cloud. The use of statistical information criterion can help determining the optimal threshold, the number of iterations to perform as well as some parameters of the underlying mathematical functions (degree of the splines, parameter representation). The resulting surfaces are well suited for analysis and computing secondary information such as contour curves and minimum and maximum points. Also deformation analysis are potential applications of fitting point clouds with LR B-splines.publishedVersio
Optimal Surface Fitting of Point Clouds Using Local Refinement : Application to GIS Data
This open access book provides insights into the novel Locally Refined B-spline (LR B-spline) surface format, which is suited for representing terrain and seabed data in a compact way. It provides an alternative to the well know raster and triangulated surface representations. An LR B-spline surface has an overall smooth behavior and allows the modeling of local details with only a limited growth in data volume. In regions where many data points belong to the same smooth area, LR B-splines allow a very lean representation of the shape by locally adapting the resolution of the spline space to the size and local shape variations of the region. The iterative method can be modified to improve the accuracy in particular domains of a point cloud. The use of statistical information criterion can help determining the optimal threshold, the number of iterations to perform as well as some parameters of the underlying mathematical functions (degree of the splines, parameter representation). The resulting surfaces are well suited for analysis and computing secondary information such as contour curves and minimum and maximum points. Also deformation analysis are potential applications of fitting point clouds with LR B-splines
S-Duct Aerodynamics: Optical Distortion Correction Methods for the Application of Particle Image Velocimetry Techniques in Convoluted Aero Engine Intakes
Complex flow phenomena and the high unsteadiness introduced by convoluted inlet ducts can compromise the performance of the downstream turbomachinery. Stereoscopic Particle Image Velocimetry has been successfully employed at Cranfield University to investigate the internal flow aerodynamics of unconventional intakes. In the present study, an optical distortion correction method based on calibration markers was developed along with an assessment of optical non linearities in PIV images
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