3d reconstruction of underwater scenes from uncalibrated video sequences

Kırlı, Mustafa Yavuz
The aim of this thesis is to reconstruct 3D representation of underwater scenes from uncalibrated video sequences. Underwater visualization is important for underwater Remotely Operated Vehicles and underwater is a complex structured environment because of inhomogeneous light absorption and light scattering by the environment. These factors make 3D reconstruction in underwater more challenging. The reconstruction consists of the following stages: Image enhancement, feature detection and matching, fundamental matrix estimation, auto-calibration, recovery of extrinsic parameters, rectification, stereo matching and triangulation. For image enhancement, a pre-processing filter is used to remove the effects of water and to enhance the images. Two feature extraction methods are examined: 1. Difference of Gaussian with SIFT feature descriptor, 2. Harris Corner Detector with grey level around the feature point. Matching is performed by finding similarities of SIFT features and by finding correlated grey levels respectively for each feature extraction method. The results show that SIFT performs better than Harris with grey level information. RANSAC method with normalized 8-point algorithm is used to estimate fundamental matrix and to reject outliers. Because of the difficulties of calibrating the cameras in underwater, auto-calibration process is examined. Rectification is also performed since it provides epipolar lines coincide with image scan lines which is helpful to stereo matching algorithms. The Graph-Cut stereo matching algorithm is used to compute corresponding pixel of each pixel in the stereo image pair. For the last stage triangulation is used to compute 3D points from the corresponding pixel pairs.


Video shot boundary detection by graph theoretic approaches
Aşan, Emrah; Alatan, Abdullah Aydın; Department of Electrical and Electronics Engineering (2008)
This thesis aims comparative analysis of the state of the art shot boundary detection algorithms. The major methods that have been used for shot boundary detection such as pixel intensity based, histogram-based, edge-based, and motion vectors based, are implemented and analyzed. A recent method which utilizes “graph partition model” together with the support vector machine classifier as a shot boundary detection algorithm is also implemented and analyzed. Moreover, a novel graph theoretic concept, “dominant...
Prioritized 3D scene reconstruction and rate-distortion efficient representation for video sequences
İmre, Evren; Alatan, Abdullah Aydın; Department of Electrical and Electronics Engineering (2007)
In this dissertation, a novel scheme performing 3D reconstruction of a scene from a 2D video sequence is presented. To this aim, first, the trajectories of the salient features in the scene are determined as a sequence of displacements via Kanade-Lukas-Tomasi tracker and Kalman filter. Then, a tentative camera trajectory with respect to a metric reference reconstruction is estimated. All frame pairs are ordered with respect to their amenability to 3D reconstruction by a metric that utilizes the baseline dis...
3d face representation and recognition using spherical harmonics
Tunçer, Fahri; Halıcı, Uğur; Department of Electrical and Electronics Engineering (2008)
In this study, a 3D face representation and recognition method based on spherical harmonics expansion is proposed. The input data to the method is range image of the face. This data is called 2.5 dimensional. Input faces are manually marked on the two eyes, nose and chin points. In two dimensions, using the marker points, the human face is modeled as two concentric half ellipses for the selection of region of interest. These marker points are also used in three dimensions to register the faces so that the n...
Morphable 3D facial animation based on thin plate splines
Erdoğdu, Aysu; Ulusoy, İlkay; Department of Electrical and Electronics Engineering (2010)
The aim of this study is to present a novel three dimensional (3D) facial animation method for morphing emotions and facial expressions from one face model to another. For this purpose, smooth and realistic face models were animated with thin plate splines (TPS). Neutral face models were animated and compared with the actual expressive face models. Neutral and expressive face models were obtained from subjects via a 3D face scanner. The face models were preprocessed for pose and size normalization. Then mus...
Multiview 3d reconstruction of a scene containing independently moving objects
Tola, Engin; Alatan, Abdullah Aydın; Department of Electrical and Electronics Engineering (2005)
In this thesis, the structure from motion problem for calibrated scenes containing independently moving objects (IMO) has been studied. For this purpose, the overall reconstruction process is partitioned into various stages. The first stage deals with the fundamental problem of estimating structure and motion by using only two views. This process starts with finding some salient features using a sub-pixel version of the Harris corner detector. The features are matched by the help of a similarity and neighbo...
Citation Formats
M. Y. Kırlı, “3d reconstruction of underwater scenes from uncalibrated video sequences,” M.S. - Master of Science, Middle East Technical University, 2008.