| 1. |
- Röding, Magnus, 1984, et al.
(författare)
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Massively parallel approximate Bayesian computation for estimating nanoparticle diffusion coefficients, sizes and concentrations using confocal laser scanning microscopy
- 2018
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Ingår i: Journal of Microscopy. - : Wiley. - 1365-2818 .- 0022-2720. ; 271:2, s. 174-182
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Tidskriftsartikel (refereegranskat)abstract
- We implement a massively parallel population Monte Carlo approximate Bayesian computation (PMC‐ABC) method for estimating diffusion coefficients, sizes and concentrations of diffusing nanoparticles in liquid suspension using confocal laser scanning microscopy and particle tracking. The method is based on the joint probability distribution of diffusion coefficients and the time spent by a particle inside a detection region where particles are tracked. We present freely available central processing unit (CPU) and graphics processing unit (GPU) versions of the analysis software, and we apply the method to characterize mono‐ and bidisperse samples of fluorescent polystyrene beads.
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| 2. |
- Bermano, A. H., et al.
(författare)
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Makeup Lamps: Live Augmentation of Human Faces via Projection
- 2017
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Ingår i: Computer Graphics Forum. - : Wiley. - 1467-8659 .- 0167-7055. ; 36:2, s. 311-323
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Tidskriftsartikel (refereegranskat)abstract
- We propose the first system for live dynamic augmentation of human faces. Using projector-based illumination, we alter the appearance of human performers during novel performances. The key challenge of live augmentation is latency - an image is generated according to a specific pose, but is displayed on a different facial configuration by the time it is projected. Therefore, our system aims at reducing latency during every step of the process, from capture, through processing, to projection. Using infrared illumination, an optically and computationally aligned high-speed camera detects facial orientation as well as expression. The estimated expression blendshapes are mapped onto a lower dimensional space, and the facial motion and non-rigid deformation are estimated, smoothed and predicted through adaptive Kalman filtering. Finally, the desired appearance is generated interpolating precomputed offset textures according to time, global position, and expression. We have evaluated our system through an optimized CPU and GPU prototype, and demonstrated successful low latency augmentation for different performers and performances with varying facial play and motion speed. In contrast to existing methods, the presented system is the first method which fully supports dynamic facial projection mapping without the requirement of any physical tracking markers and incorporates facial expressions.
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| 3. |
- Billeter, Markus, 1984, et al.
(författare)
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A LED-Based IR/RGB End-to-End Latency Measurement Device
- 2017
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Ingår i: Adjunct Proceedings of IEEE International Symposium on Mixed and Augmented Reality 2016. ; , s. 184-188
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Konferensbidrag (refereegranskat)abstract
- Achieving a minimal latency within augmented reality (AR) systems is one of the most important factors to achieve a convincing visual impression. It is even more crucial for non-video augmentations such as dynamic projection mappings because, in that case, the superimposed imagery has to exactly match the dynamic real surface, which obviously cannot be directly influenced or delayed in its movement. In those cases, the inevitable latency is usually compensated for using prediction and extrapolation operations, which require accurate information about the occurring overall latency to exactly predict to the right time frame for the augmentation. Different strategies have been applied to accurately compute this latency. Since some of these AR systems operate within different spectral bands for input and output, it is not possible to apply latency measurement methods encoding time stamps directly into the presented output images as these might not be sensed by used input device. We present a generic latency measurement device which can be used to accurately measure the overall end-to-end latency of camera-based AR systems with an accuracy below one millisecond. It comprises a LED-based time stamp generator displaying the time as a gray code on spatially and spectrally multiple locations. It is controlled by a micro-controller and sensed by an external camera device observing the output display as well as the LED device at the same time.
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| 4. |
- Billeter, Markus, 1984, et al.
(författare)
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Efficient stream compaction on wide SIMD many-core architectures
- 2009
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Ingår i: Proceedings of the Conference on High Performance Graphics. - 9781605586038 ; 2009, s. 159-166
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Konferensbidrag (refereegranskat)abstract
- Stream compaction is a common parallel primitive used to remove unwanted elements in sparse data. This allows highly parallel algorithms to maintain performance over several processing steps and reduces overall memory usage.For wide SIMD many-core architectures, we present a novel stream compaction algorithm and explore several variations thereof. Our algorithm is designed to maximize concurrent execution, with minimal use of synchronization. Bandwidth and auxiliary storage requirements are reduced significantly, which allows for substantially better performance.We have tested our algorithms using CUDA on a PC with an NVIDIA GeForce GTX280 GPU. On this hardware, our reference implementation provides a 3x speedup over previous published algorithms.
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| 5. |
- Billeter, Markus, 1984
(författare)
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Real-Time GPU Algorithms: Parallel Primitives and Rendering of Participating Media
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Modern graphics processing units, GPUs, present an immense resource of computational power, that however remains challenging to fully harness. This thesis explores four algorithms and methods that attempt to take full advantage of the resources provided by a GPU. The algorithms focus on efficient implementations that perform well enough to be considered for real-time applications.Two of the papers focus on using GPUs to accelerate general purpose algorithms by leveraging general purpose GPU, GPGPU, techniques. First, general purpose parallel primitives such as parallel stream compaction, reduction, prefix sums and sorting are presented. The second paper applies these techniques to efficiently build a two-level hierarchical grid from scene geometry. The two-level grid is then used to accelerate ray tracing. While ray tracing is related to computer graphics, it is outside of the traditional scope of GPUs, which are built to mainly accelerate rasterized graphics.In the third paper, the rasterization specific parts of a modern GPU are leveraged to render shafts of light and other effects that single scattering of light in a participating medium gives rise to. The method presented in the third paper relies on shadow maps to generate polygonal geometry enclosing space that is directly illuminated by a light source. It is inside this geometry that single scattering takes place.The final paper explores the combination of GPGPU techniques with traditional graphics operations. The method augments the single scattering algorithms presented in the third paper with support for multiple scattering and indirect illumination of geometry by light scattered in the participating medium. It uses light propagation volumes, LPVs, which are efficiently implemented using GPGPU programming techniques to propagate light using a modified propagation scheme that accounts for scattering in the medium.
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| 6. |
- Billeter, Markus, 1984
(författare)
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Real-Time GPU Techniques for Advanced Lighting Phenomena
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the real world, the visual perception of an object is completely determined by the object's interactions with light. One large application of computer graphics is to visualize virtual objects and worlds in a fashion that is familiar to humans. Successfully emulating light and its effects on virtual objects therefore plays a central role.The papers included in this thesis mainly explore improved methods of computing the effects of light in various settings. The focus is on doing so in real-time for interactive applications. Two papers target capturing the visual effects of light traveling through a participating medium (a medium such as fog or smog). The first of these papers presents a method that can be used to render shafts of light/volumetric shadows in real time. The second paper extends this to include additional effects associated with participating media, including, for example, indirect illumination of surfaces from light scattered in the medium.Next, two papers explore real-time rendering with many light sources. One paper presents a method to efficiently render in the presence of and manage thousands of light sources and demonstrates scaling up to one million lights. The other paper focuses on rendering on mobile devices (such as smartphones and tablet devices), and investigates the possibility of off-loading rendering tasks to a remote server. The paper presents one approach where a server computes indirect illumination represented by virtual light sources. The client retrieves these virtual light sources from the server and uses an adapted version of the previously presented many-lights technique for rendering.Graphics processing units (GPUs) play a central role in all these techniques. Thus, the first paper included in this thesis discusses efficient implementations of fundamental building blocks for programming GPUs. In particular, it presents an efficient implementation of the stream compaction operation. It further discusses the programming strategy that makes the implementation efficient and demonstrates several related fundamental operations developed using that strategy.
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| 7. |
- Billeter, Markus, 1984, et al.
(författare)
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Real-Time Multiple Scattering using Light Propagation Volumes
- 2012
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Ingår i: Proceedings - I3D 2012: ACM SIGGRAPH Symposium on Interactive 3D Graphics and Games. 2012 16th ACM SIGGRAPH Symposium on Interactive 3D Graphics and Games, I3D 2012, Costa Mesa, CA, 9-11 March 2012. - New York, NY, USA : ACM. - 9781450311946 ; , s. 119-126
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Konferensbidrag (refereegranskat)abstract
- This paper introduces a new GPU-based, real-time method for rendering volumetric lighting effects produced by scattering in a participating medium. The method includes support for indirect illumination by scattered light, high-quality single-scattered volumetric shadows, and approximate multiple scattered volumetric lighting effects in isotropic and homogeneous media. The method builds upon an improved propagation scheme for light propagation volumes. This scheme models scattering according to the radiative light transfer equation during propagation. The initial state of the light propagation volumes is based on single-scattered light identified with shadow maps; this allows generation of a high quality initial distribution of radiance. After propagation, the resulting distribution is used as a source of diffuse light during rendering and is also ray marched for volumetric effects from multiple scattering. Volumetric shadows from single-scattered light are rendered separately. We compare the new method to single-scattered volumetric shadows produced by contemporary techniques, plain light propagation volumes (which this new method extends), and a simple composition thereof.
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| 8. |
- Billeter, Markus, 1984, et al.
(författare)
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Real Time Volumetric Shadows using Polygonal Light Volumes
- 2010
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Ingår i: Proceedings of the Conference on High Performance Graphics, 2010. - 2079-8679. - 9783905674262 ; , s. 39-45
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Konferensbidrag (refereegranskat)abstract
- This paper presents a more efficient way of computing single scattering effects in homogeneous participating media for real-time purposes than the currently popular ray-marching based algorithms. These effects include halos around light sources, volumetric shadows and crepuscular rays. By displacing the vertices of a base mesh with the depths from a standard shadow map, we construct a polygonal mesh that encloses the volume of space that is directly illuminated by a light source. Using this volume we can calculate the airlight contribution for each pixel by considering only points along the eye-ray where shadow-transitions occur. Unlike previous ray-marching methods, our method calculates the exact airlight contribution, with respect to the shadow map resolution, at real time frame rates.
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| 9. |
- Billeter, Markus, 1984, et al.
(författare)
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Tiled Forward Shading
- 2013
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Ingår i: GPU Pro 4: Advanced Rendering Techniques. - : A K Peters/CRC Press. ; , s. 99-114
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- We will explore the tiled forward shading algorithm in this chapter. Tiledforward shading is an extension or modification of tiled deferred shad-ing [Balestra and Engstad 08,Swoboda 09,Andersson 09,Lauritzen 10,Olssonand Assarsson 11], which itself improves upon traditional deferred shadingmethods [Hargreaves and Harris 04, Engel 09]. Tiled forward rendering attempts to combine one of the main advantages of (tiled) deferred rendering, i.e. the reduced amount of lighting computations done, with the advantages of forward rendering. Besides reduced memory requirements (forward rendering does not need the large G-buffer), it also enables transparency [Kircher and Lawrance 09, Enderton et al. 10], multi-sampling schemes [Swoboda 09,Lauritzen 10] and does not force the use of ubershaders if different shading models must be supported.
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| 10. |
- Kalojanov, Javor, et al.
(författare)
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Two-Level Grids for Ray Tracing on GPUs
- 2011
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Ingår i: Computer Graphics Forum. - : Wiley. - 1467-8659 .- 0167-7055. ; 30:2, s. 307-314
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the use of two-level nested grids as acceleration structure for ray tracing of dynamic scenes. We propose a massively parallel, sort-based construction algorithm and show that the two-level grid is one of the structures that is fastest to construct on modern graphics processors. The structure handles non-uniform primitive distributions more robustly than the uniform grid and its traversal performance is comparable to those of other high quality acceleration structures used for dynamic scenes. We propose a cost model to determine the grid resolution and improve SIMD utilization during ray-triangle intersection by employing a hybrid packetization strategy. The build times and ray traversal acceleration provide overall rendering performance superior to previous approaches for real time rendering of animated scenes on GPUs.
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