3D object reconstruction using computer vision : reconstruction and characterization applications for external human anatomical structures

Tese de doutoramento. Engenharia Informática. Faculdade de Engenharia. Universidade do Porto. 201

Multiple Representation Approach to Geometric Model Construction From Range Data

A method is presented for constructing geometric design data from noisy 3-D sensor measurements of physical parts. In early processing phase, RLTS regression filters stemming from robust estimation theory are used for separating the desired part of the signal in contaminated sensor data from undesired part. Strategies for producing a complete 3-D data set from partial views are studied. Multiple representations are used in model construction because there is no single representation that would be most appropriate in all situations. In particular, surface triangulation, NURBS, and super-ellipsoids are employed in order to represent efficiently polygonal and irregular shapes, free form surfaces and standard primitive solids. The size of the required control point mesh for spline description is estimated using a surface characterization process. Surfaces of arbitrary topology are modeled using triangulation and trimmed NURBS. A user given tolerance value is driving refinement of the obtained surface model. The resulting model description is a procedural CAD model which can convey structural information in addition to low level geometric primitives. The model is translated to IGES standard product data exchange format to enable data sharing with other processes in concurrent engineering environment. Preliminary results on view registration using simulated data are shown. Examples of model construction using both real and simulated data are also given

Plethora : a framework for the intelligent control of robotic assembly systems

Plethora : a framework for the intelligent control of robotic assembly system

ARCHITECTURE ESTIMATION FROM SPARSE IMAGES USING GRAMMATICAL SHAPE PRIORS FOR CULTURAL HERITAGE

The estimation and reconstruction of 3D architectural structures is of great in- terest in computer vision, as well as cultural heritage. This dissertation proposes a novel approach to solve the di??cult problem of estimating architectural structures from sparse images and e??ciently generating 3D models from estimation results for cultural heritage. This approach takes as input one plan drawing image and a few fac¸ade images, and provides as output the volumetric 3D models which represent the structures in the sparse images. Support of this research goal has motivated new investigations in underlying structure estimation problems including detecting structural feature points in 2D images, decomposing plan drawings into semantically meaningful shapes for medieval castles, estimating rectangular and Gothic fac¸ades using shape priors, and estimating complete 3D models for architectural structures using a novel volumetric shape grammar. Major outstanding challenges in each of these topic areas are addressed resulting in contributions to current state-of-the-art as it applied to these di??cult problems

FAST AND RELIABLE OBJECT CLASSIFICATION IN VIDEO BASED ON A 3D GENERIC MODEL

International audienceWe propose a new object classification approach for monocular video sequences, which allows to classify objects modelled independently from the camera position and object orientation. To achieve this independence, a simple 3D object model that represents an object as a parallelepiped is proposed. The approach is able to give good estimates of object dimensions and proposes visual reliability measures for the object dimensions. These measures give a representation of the visibility of the estimated dimension and are principally proposed to aid posterior phases of the video understanding process, as object tracking and event detection. The method obtains the 3D parallelepiped model estimation using a set of 2D moving regions (obtained in a segmentation phase), the perspective matrix transform (obtained from camera calibration using the pin-hole camera model) and predefined 3D models of expected objects in the scene. After classification, a merging step is performed to improve the classification performance by assembling 2D moving regions with better 3D model probability when together. This approach shows promising results on object classification, obtaining very high detection rates for complex situations and performing at video frame rate

Vision-assisted modeling for model-based video representations

Thesis (Ph. D.)--Massachusetts Institute of Technology, Program in Media Arts & Sciences, 1997.Includes bibliographical references (leaves 134-145).by Shawn C. Becker.Ph.D

3D Visualization using virtual view generation for stereoscopic hardware

To summarize, the final purpose is to create a compact tool that generates virtual stereo views at a desired position, being able to move and rotate it, from the information of several cameras spread in the area. These views will allow to visualize the scene in 3D, using a device that reproduces the stereoscopic effect, from the current point of vie

Study of pedestrian impact on headlamp

The main objective in this pedestrian impact study is a correlation between the computer simulations and the basic pendulum test rig in order to propose solutions that may improve the compliance of the headlamps without affecting their basic performance. Firstly, a tensile test at three different velocities was conducted to study the strain caused by applying a load within a certain time over a dog-bone specimen and the strain rate dependency of polycarbonate was demonstrated. Despite creating a LS-DYNA model and a material card, the decision was to use the material card provided by JLR for conducting the numerical simulations. Later, five impact test simulations were conducted for two different scenarios. The first one was with the headlamp fixed on its four attachments but it resulted that the fracture of the mountings, even with a low impact energy of 50J. As a consequence, EPP foam is used as the support in the second scenario. Then, a pendulum test rig was designed, built and used for impact tests. Unfortunately, due to the problems with the pendulum structure, only the 50J test was conducted. Four tests were made in order to have enough data to correlate the numerical simulations with the impact tests. The pendulum was instrumented with 1kN and 5kN load cells, which were statically calibrated and connected to a data acquisition system to obtain experimental data. A correlation stage was held and it was noticed that the peak value of the impact force did not match the simulated result. This may have been partly due to the low data acquisition rate achievable in the available instrumentation. Finally, a parametric improvement study involving three different design parameters is proposed. As a valid correlation was not achieved, these improvements were not conducted and are recommended for future studies.Outgoin