Browsing by Subject "Ray tracing"
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Item Open Access Bounding volume hierarchy-tetrahedralization hybrid acceleration structure for ray tracing(2020-12) Demirci, SerkanThe computational cost of the ray-tracing method is directly proportional to the number of ray-surface intersection tests. The naive ray-tracing algorithm requires O(N) computational cost for the ray-surface intersection calculations where N is the number of primitives in the scene. Ray tracing acceleration data structures like the regular grid, bounding volume hierarchy (BVH), kd-tree, constrained tetrahedralization, has been developed to reduce the number of rayobject intersection tests to speed-up ray tracing. We propose a hybrid acceleration structure, the Bounding Volume HierarchyTetrahedral mesh hybrid (BTH) acceleration structure, that can be used to speedup ray tracing. BTH structure is composed of a BVH hierarchy where some of the leaves of the BVH hierarchy contain tetrahedralizations. We propose an algorithm for the construction of the BTH structure. We describe methods for approximating the average nearest-hit cost of a tetrahedralization, which we use for the construction of BTH. Besides, we can adapt the proposed BTH structure for dynamic scenes with hierarchical motion. We describe a two-level BVH-BTH acceleration structure for rendering animated scenes. We test the proposed BTH structure using various scenes. For some of the experiments, the BTH structure performs better against other acceleration structures in terms of rendering times. We perform experiments for animated scenes. We show that the two-level BTH structure outperforms the two-level BVH structure for the tested dynamic scenes.Item Open Access Compact tetrahedralization-based acceleration structures for ray tracing(Springer, 2022-10) Aman, Aytek; Demirci, Serkan; Güdükbay, UğurWe propose compact and efficient tetrahedral mesh representations to improve the ray-tracing performance. We reorder tetrahedral mesh data using a space-filling curve to improve cache locality. Most importantly, we propose efficient ray-traversal algorithms. We provide details of the regular ray-tracing operations on tetrahedral meshes and the GPU implementation of our traversal method. We demonstrate our findings through a set of comprehensive experiments. Our method outperforms existing tetrahedral mesh-based traversal methods and yields comparable results to the traversal methods based on the state-of-the-art acceleration structures such as k-dimensional (k-d) tree and Bounding Volume Hierarchy (BVH) in terms of speed. Storage-wise, our method uses less memory than its tetrahedral mesh-based counterparts, thus allowing larger scenes to be rendered on the GPU. Graphic Abstract: [Figure not available: see fulltext.] © 2022, The Visualization Society of Japan.Item Open Access Hardware-accelerated direct visualization of unstructured volumetric meshes(2022-07) Şahıstan, AlperComputational fluid dynamic simulations often produce large clusters of finite ele-ments with non-trivial, non-convex boundaries and uneven distributions among com-pute nodes, posing challenges to compositing during interactive volume rendering. Correct, in-place visualization of such clusters becomes difficult because viewing rays straddle domain boundaries across multiple compute nodes. We propose a GPU-based, scalable, memory-efficient direct volume visualization framework suitable for in situ and post hoc usage. Our approach reduces memory usage of the unstructured volume elements by leveraging an exclusive or-based index reduction scheme and provides fast ray-marching-based traversal without requiring large external data structures built over the elements. Moreover, we present a GPU-optimized deep compositing scheme that allows correct order compositing of intermediate color values accumulated across different ranks that works even for non-convex clusters. Furthermore, we illustrate that we can achieve secondary effects such as shadows and gradient shading using our method for single GPU setups. Our approach scales well on large data-parallel sys-tems and achieves interactive frame rates during visualization. We can interactively render Fun3D Small Mars Lander (14 GB / 798.4 million finite elements) and Huge Mars Lander (111.57 GB / 6.4 billion finite elements) data sets at 14 and 10 frames per second using 72 and 80 GPUs, respectively, on the Frontera supercomputer at The Texas Advanced Computing Center (TACC).Item Open Access Modelling a resistive-reflector antenna by the complex source-dual series approach: the 2-D case of H-polarization(IEEE, 1995) Altıntaş, Ayhan; Nosich, A. I.; Yurchenko, V. B.The simulation of reflector antenna is normally conducted under an assumption of the perfect conductivity of reflector. This paper presents an analysis of resistive reflector beamforming using modified method of regularization for solving the scattering from a curve resistive strip. Besides, to simulate a directive feed in equally accurate manner, the Complex Source Method is used.Item Open Access Multi-level tetrahedralization-based accelerator for ray-tracing animated scenes(John Wiley & Sons Ltd., 2021-06-01) Aman, Aytek; Demirci, Serkan; Güdükbay, Uğur; Wald, I.We describe a hybrid acceleration structure for ray tracing. The hybrid structure is a Bounding Volume Hierarchy (BVH) where the leaf nodes are tetrahedralized for a decent ray-surface intersection performance. We use the hybrid acceleration structure (BTH) in a two-level acceleration structure for rendering animated scenes. There is a BVH at the top level in this two-level structure and the proposed hybrid structure (BTH) at the bottom level. We test the proposed two-level structure (BVH-BTH) for various animated scenes and obtained promising results against other acceleration structures in terms of rendering times. The two-level BVH-BTH structure outperforms the two-level BVH structure for the tested dynamic scenes.Item Open Access Quick clusters: a GPU-Parallel partitioning for efficient path tracing of unstructured volumetric grids(Institute of Electrical and Electronics Engineers, 2022-09-22) Morrical, Nate; Şahistan, Alper; Uğur, Güdükbay; Wald, Ingo; Pascucci, ValerioWe propose a simple yet effective method for clustering finite elements to improve preprocessing times and rendering performance of unstructured volumetric grids without requiring auxiliary connectivity data. Rather than building bounding volume hierarchies (BVHs) over individual elements, we sort elements along with a Hilbert curve and aggregate neighboring elements together, improving BVH memory consumption by over an order of magnitude. Then to further reduce memory consumption, we cluster the mesh on the fly into sub-meshes with smaller indices using a series of efficient parallel mesh re-indexing operations. These clusters are then passed to a highly optimized ray tracing API for point containment queries and ray-cluster intersection testing. Each cluster is assigned a maximum extinction value for adaptive sampling, which we rasterize into non-overlapping view-aligned bins allocated along the ray. These maximum extinction bins are then used to guide the placement of samples along the ray during visualization, reducing the number of samples required by multiple orders of magnitude (depending on the dataset), thereby improving overall visualization interactivity. Using our approach, we improve rendering performance over a competitive baseline on the NASA Mars Lander dataset from 6× (1 frame per second (fps) and 1.0 M rays per second (rps) up to now 6 fps and 12.4 M rps , now including volumetric shadows) while simultaneously reducing memory consumption by 3× (33 GB down to 11 GB) and avoiding any offline preprocessing steps, enabling high-quality interactive visualization on consumer graphics cards. Then by utilizing the full 48 GB of an RTX 8000, we improve the performance of Lander by 17 × (1 fps up to 17 fps, 1.0 M rps up to 35.6 M rps) .Item Open Access Ray tracing geometric models and parametric surfaces(1989) İşler, VeysiIn many computer graphics applications such as CAD, realistic displays have very important and positive effects on designers using the system. There axe several techniques to generate realistic images with the computer. Ray tracing gives the most effective results by simulating the interaction of light with its environment. Furthermore, this technique can be easily adopted to many physical phenomena such as reflection, refraction, shadows, etc. by which the interaction of many different objects with each other could be realistically simulated. However, it may require excessive amount of time to generate an image. In this thesis , we studied the ray tracing algorithm arid the speed problem associated with it and several methods developed to overcome this problem. We also implemented a ray tracer system that could be used to model a three dimensional scene and And out the lighting effects on the objects.Item Open Access Rendering three-dimensional scenes with tetrahedral meshes(2022-07) Aman, AytekWe propose compact and efficient tetrahedral mesh representations to improve the ray-tracing performance. We reorder tetrahedral mesh data using a space-filling curve to improve cache locality. Most importantly, we propose efficient ray traversal algorithms. We provide details of the regular ray tracing operations on tetrahedral meshes and the Graphics Processing Unit (GPU) implementation of our traversal method. We demonstrate our findings through a set of comprehensive experiments. Our method outperforms existing tetrahedral mesh-based traversal methods and yields comparable results to the traversal methods based on the state-of-the-art acceleration structures such as k-dimensional (k-d) tree and Bounding Volume Hierarchy (BVH) in terms of speed. Storage-wise, our method uses less memory than its tetrahedral mesh-based counterparts, thus allowing larger scenes to be rendered on the GPU. We also describe additional applications of our technique specifically for volume rendering, two-level hybrid acceleration structures for animation purposes, and point queries in two-dimensional (2-D) and three-dimensional (3-D) triangulations. Finally, we present a practical method to tetrahedralize very large scenes.Item Open Access Resonance lens antenna analysis for MM-wave applications(IEEE, 2004-06) Boriskin, A. V.; Nosich, A. I.; Boriskina, S. V.; Sewell, P.; Benson, T. M.; Altıntaş, AyhanWe report what is to our knowledge the first accurate theoretical investigation of the electromagnetic behavior of 2-D elliptical lenses of finite wavelength-scale size. The role of internal resonances in the focal domain formation is studied. A proposal of a narrow-band receiver based on a hemielliptic lens tuned to a resonance is discussed. Possible features of such a lens-coupled receiver are stability of the resonance field with respect to the angle of arrival of incident wave and several times greater values of the peak field intensity that may potentially lead to higher sensitivity and better scanning performance. In the analysis, we use the Muller boundary integral equation (BIE) technique. This full-wave mathematically rigorous method is combined with trigonometric Galerkin discretization to result in the efficient numerical solution for an arbitrary set of the electrical, geometrical, and material parameters. Numerical results are generated for a quartz elliptical lens (ε= 3.8) with dimensions typical to mm-wave radar applications. Near field analysis, lens-focusing properties and lens frequency-dependent performance are presented.Item Open Access Space weather studies of IONOLAB group(IEEE, 2016) Arıkan, F.; Sezen, U.; Toker, C.; Artuner, H.; Bulu, G.; Demir, U.; Erdem, E.; Arıkan, Orhan; Tuna, Hakan; Gulyaeva, T. L.; Karatay, S.; Mosna, Z.IONOLAB is an interdisciplinary research group dedicated for handling the challenges of near earth environment on communication, positioning and remote sensing systems. IONOLAB group contributes to the space weather studies by developing state-of-the-art analysis and imaging techniques. On the website of IONOLAB group, www.ionolab.org, four unique space weather services, namely, IONOLAB-TEC, IRI-PLAS-2015, IRI-PLAS-MAP and IRI-PLAS-STEC, are provided in a user friendly graphical interface unit. Newly developed algorithm for ionospheric tomography, IONOLAB-CIT, provides not only 3-D electron density but also tracking of ionospheric state with high reliability and fidelity. The algorithm for ray tracing through ionosphere, IONOLAB-RAY, provides a simulation environment in all communication bands. The background ionosphere is generated in voxels where IRI-Plas electron density is used to obtain refractive index. One unique feature is the possible update of ionospheric state by insertion of Total Electron Content (TEC) values into IRI-Plas. Both ordinary and extraordinary paths can be traced with high ray and low ray scenarios for any desired date, time and transmitter location. 2-D regional interpolation and mapping algorithm, IONOLAB-MAP, is another tool of IONOLAB group where automatic TEC maps with Kriging algorithm are generated from GPS network with high spatio-temporal resolution. IONOLAB group continues its studies in all aspects of ionospheric and plasmaspheric signal propagation, imaging and mapping.Item Open Access Spatial subdivision for parallel ray casting/tracing(1995) İşler, VeysiRay casting/tracing has been extensively studied for a long time, since it is an elegant way of producing realistic images. However, it is a computationally intensive algorithm. In this study, a taxonomy of parallel ray casting/tracing algorithms is presented cind the primary parallel ray casting/tracing systems are discussed and criticized. This work mainly focuses on the utilization of spatial subdivision technique for ray casting/tracing on a distributed-memory MIMD parallel computer. In this research, the reason for the use of parallel computers is not only the processing power but also the large memory space provided by them. The spatial subdivision technique has been adapted to parallel ray casting/tracing to decompose a three-dimensional complex scene that may not fit into the local memory of a single processor. The decomposition method achieves an even distribution of scene objects while allowing to exploit graphical coherence. Additionally, the decomposition method produces three-dimensional volumes which are mapped inexpensively to the processors so that the objects within adjacent volumes are stored in the local memories of close processors to decrease interprocessor communication cost. Then, the developed decomposition and mapping methods have been parallelized efficiently to reduce the preprocessing overhead. Finally, a splitting plane concept (called “jaggy splitting plane”) has been proposed to accomplish full utilization of the memory space of processors. Jaggy splitting plane avoids the shared objects which are the major sources of inefficient utilization of both memory and processing power. The proposed parallel algorithms have been implemented on the Intel iPSC/2 hypercube multicomputer (distributed-memory MIMD).Item Open Access State-of-the-art in large-scale volume visualization beyond structured data(Eurographics and John Wiley & Sons Ltd., 2023-06-27) Sarton, J.; Zellmann, S.; Demirci, Serkan; Güdükbay, Uğur; Alexandre-Barff, W.; Lucas, L.; Dischler, J. M.; Wesner, S.; Wald, I.; Alliez, Pierre; Wimmer, MichaelVolume data these days is usually massive in terms of its topology, multiple fields, or temporal component. With the gap between compute and memory performance widening, the memory subsystem becomes the primary bottleneck for scientific volume visualization. Simple, structured, regular representations are often infeasible because the buses and interconnects involved need to accommodate the data required for interactive rendering. In this state-of-the-art report, we review works focusing on large-scale volume rendering beyond those typical structured and regular grid representations. We focus primarily on hierarchical and adaptive mesh refinement representations, unstructured meshes, and compressed representations that gained recent popularity. We review works that approach this kind of data using strategies such as out-of-core rendering, massive parallelism, and other strategies to cope with the sheer size of the ever-increasing volume of data produced by today's supercomputers and acquisition devices. We emphasize the data management side of large-scale volume rendering systems and also include a review of tools that support the various volume data types discussed.Item Open Access Turkey: State of the art in computer graphics-The Turkish scene(1996) Özgüç, B.[No abstract available]