Research Outputs
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Publication Restricted 3D Display system using scanning LED array modules(Koç University, 2008) Sayınta, Murat; Ürey, Hakan; 0000-0002-2031-7967; Koç University Graduate School of Sciences and Engineering; Electrical and Computer Engineering; 8579
Publication Metadata only 3D progressive compression with octree particles(Akademische Verlagsgesellsch Aka Gmbh, 2002) Schmitt, Francis; Department of Computer Engineering; N/A; Yemez, Yücel; Faculty Member; Department of Computer Engineering; College of Engineering; N/A; 107907; N/AThis paper improves the storage efficiency of the progressive particle-based modeling scheme presented in [14, 15] by using entropy coding techniques. This scheme encodes the surface geometry and attributes in terms of appropriately ordered oc-tree particles, which can then progressively be decoded and rendered by the-viewer by means of a fast direct triangulation technique. With the introduced entropy coding technique, the bitload of the multi-level representation for geometry encoding reduces to 9-14 bits per particle (or 4.5-7 bits per triangle) for 12-bit quantized geometry.Publication Metadata only 3D shape correspondence by isometry-driven greedy optimization(IEEE Computer Soc, 2010) N/A; Department of Computer Engineering; Sahillioğlu, Yusuf; Yemez, Yücel; PhD Student; Faculty Member; Department of Computer Engineering; Graduate School of Sciences and Engineering; College of Engineering; 215195; 107907We present an automatic method that establishes 3D correspondence between isometric shapes. Our goal is to find an optimal correspondence between two given (nearly) isometric shapes, that minimizes the amount of deviation from isometry. We cast the problem as a complete surface correspondence problem. Our method first divides the given shapes to be matched into surface patches of equal area and then seeks for a mapping between the patch centers which we refer to as base vertices. Hence the correspondence is established in a fast and robust manner at a relatively coarse level as imposed by the patch radius. We optimize the isometry cost in two steps. in the first step, the base vertices are transformed into spectral domain based on geodesic affinity, where the isometry errors are minimized in polynomial time by complete bipartite graph matching. the resulting correspondence serves as a good initialization for the second step of optimization in which we explicitly minimize the isometry cost via an iterative greedy algorithm in the original 3D Euclidean space. We demonstrate the performance of our method on various isometric (or nearly isometric) pairs of shapes for some of which the ground-truth correspondence is available.Publication Metadata only 3D Shape recovery and tracking from multi-camera video sequences via surface deformation(IEEE, 2006) Skala, V.; N/A; Department of Computer Engineering; Sahillioğlu, Yusuf; Yemez, Yücel; PhD Student; Faculty Member; Department of Computer Engineering; Graduate School of Sciences and Engineering; College of Engineering; 215195; 107907This paper addresses 3D reconstruction and modeling of time-varying real objects using multicamera video. The work consists of two phases. In the first phase, the initial shape of the object is recovered from its silhouettes using a surface deformation model. The same deformation model is also employed in the second phase to track the recovered initial shape through the time-varying silhouette information by surface evolution. The surface deformation/evolution model allows us to construct a spatially and temporally smooth surface mesh representation having fixed connectivity. This eventually leads to an overall space-time representation that preserves the semantics of the underlying motion and that is much more efficient to process, to visualize, to store and to transmit.Publication Metadata only A new scalable multi-view video coding configuration for robust selective streaming of free-viewpoint TV(IEEE, 2007) Özbek, Nükhet; Tunalı, E. Turhan; Department of Electrical and Electronics Engineering; Tekalp, Ahmet Murat; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 26207Free viewpoint TV (FTV) is a new media format that allows a user to change his/her viewpoint freely. To this effect, multi-view video must be coded to sAtışfy two conflicting requirements: i) achieve high compression efficiency, and ii) allow view switching with low delay. This paper proposes a new encoding configuration for scalable multi-view video coding, which achieves a compromise between the two requirements. In the new scalable multi-view configuration, the base layer is encoded with inter-view prediction at a minimum acceptable quality, while enhancement layers for each view only depend on their respective base layers (with no interview prediction). Thus, the base layer shall be served to all users, while enhancement layers shall be served selectively to users depending on their channel bandwidth and viewing direction. We compare the compression efficiency of the proposed method with those of non-scalable multi-view coding (MVC) and simulcast (H.264/AVC of each view independently) solutions.Publication Restricted Augmented reality 3D display and light field imaging systems based on passive optical surfaces(Koç University, 2018) Soomro, Shoaib Rehman; Ürey, Hakan; 0000-0002-2031-7967; Koç University Graduate School of Sciences and Engineering; Electrical and Electronics Engineering; 8579Publication Restricted Exploring mixed and multi-precision SpMV fpr GPUs(Koç University, 2022) Tezcan, Erhan; Erten, Didem Unat; 0000-0002-2351-0770; Koç University Graduate School of Sciences and Engineering; Computer Science and Engineering; 219274Publication Metadata only H.264 long-term reference selection for videos with frequent camera transitions(IEEE, 2006) Özbek, Nükhet; Department of Electrical and Electronics Engineering; Tekalp, Ahmet Murat; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 26207Long-tern reference prediction is an important feature of the H.264/MPEG-4 AVC standard, which provides a tradeoff between compression gain and computational complexity. In this study, we propose a long-tern reference selection method for videos with frequent camera transitions to optimize compression efficiency at shot boundaries without increasing the computational complexity. Experimental results show up to 50% reduction in the number of bits (at the same PSNR) for frames at the border of camera transitions.Publication Restricted Hardwaresoftware design and implementation of a laser scanning confocal microscope controller using open design approach(Koç University, 2015) Yalçın, Baran; Kiraz, Alper; 0000-0001-7977-1286; Koç University Graduate School of Sciences and Engineering; Optoelectronics and Photonics Engineering; 22542Publication Metadata only Hierarchical representation and coding of 3D mesh geometry for transmission of surface/volume data(IEEE, 2006) Celasun, Işıl; Eröksüz, Serkan; Siddiqui, Rizwan A.; Doğan, Ertuğrul; Department of Electrical and Electronics Engineering; Tekalp, Ahmet Murat; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 26207Hierarchical mesh representation and mesh simplification have been addressed in computer graphics for adaptive level-of-detail rendering of 3D objects. In this paper, by using a new simplification method to design hierarchical 3D meshes such that each mesh level has Delaunay topology, we can obtain not only meshes with desired geometric properties, but also efficient compression of the mesh data. The hierarchical compression technique is based on a nearest-neighbor ordering of mesh node points. The baseline is the use of entropy coding of linear prediction between nearest neighbor node coordinates. Vector quantization is also employed just to be able to process efficiently stAtıştical dependences between prediction error vectors of a node. The compression method allows progressive transmission and quality scalability.
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