61 research outputs found
OpenGL-assisted Visibility Queries of Large Polygonal Models
Veröffentlichung des Wilhelm-Schickard-Institut für Informatik Universität Tübinge
Interactive global illumination on the CPU
Computing realistic physically-based global illumination in real-time remains one
of the major goals in the fields of rendering and visualisation; one that has not
yet been achieved due to its inherent computational complexity. This thesis focuses
on CPU-based interactive global illumination approaches with an aim to
develop generalisable hardware-agnostic algorithms. Interactive ray tracing is reliant
on spatial and cache coherency to achieve interactive rates which conflicts
with needs of global illumination solutions which require a large number of incoherent
secondary rays to be computed. Methods that reduce the total number of
rays that need to be processed, such as Selective rendering, were investigated to
determine how best they can be utilised.
The impact that selective rendering has on interactive ray tracing was analysed
and quantified and two novel global illumination algorithms were developed,
with the structured methodology used presented as a framework. Adaptive Inter-
leaved Sampling, is a generalisable approach that combines interleaved sampling
with an adaptive approach, which uses efficient component-specific adaptive guidance
methods to drive the computation. Results of up to 11 frames per second
were demonstrated for multiple components including participating media. Temporal Instant Caching, is a caching scheme for accelerating the computation of
diffuse interreflections to interactive rates. This approach achieved frame rates
exceeding 9 frames per second for the majority of scenes. Validation of the results
for both approaches showed little perceptual difference when comparing
against a gold-standard path-traced image. Further research into caching led to
the development of a new wait-free data access control mechanism for sharing the
irradiance cache among multiple rendering threads on a shared memory parallel
system. By not serialising accesses to the shared data structure the irradiance
values were shared among all the threads without any overhead or contention,
when reading and writing simultaneously. This new approach achieved efficiencies
between 77% and 92% for 8 threads when calculating static images and animations.
This work demonstrates that, due to the
flexibility of the CPU, CPU-based
algorithms remain a valid and competitive choice for achieving global illumination
interactively, and an alternative to the generally brute-force GPU-centric
algorithms
Time-varying volume visualization
Volume rendering is a very active research field in Computer Graphics because of its wide range of applications in various sciences, from medicine to flow mechanics. In this report, we survey a state-of-the-art on time-varying volume rendering. We state several basic concepts and then we establish several criteria to classify the studied works: IVR versus DVR, 4D versus 3D+time, compression techniques, involved architectures, use of parallelism and image-space versus object-space coherence. We also address other related problems as transfer functions and 2D cross-sections computation of time-varying volume data. All the papers reviewed are classified into several tables based on the mentioned classification and, finally, several conclusions are presented.Preprin
Efficient global illumination for dynamic scenes
The production of high quality animations which feature compelling lighting effects is computationally a very heavy task when traditional rendering approaches are used where each frame is computed separately. The fact that most of the computation must be restarted from scratch for each frame leads to unnecessary redundancy. Since temporal coherence is typically not exploited, temporal aliasing problems are also more difficult to address. Many small errors in lighting distribution cannot be perceived by human observers when they are coherent in temporal domain. However, when such a coherence is lost, the resulting animations suffer from unpleasant flickering effects. In this thesis, we propose global illumination and rendering algorithms, which are designed specifically to combat those problems. We achieve this goal by exploiting temporal coherence in the lighting distribution between the subsequent animation frames. Our strategy relies on extending into temporal domain wellknown global illumination and rendering techniques such as density estimation path tracing, photon mapping, ray tracing, and irradiance caching, which have been originally designed to handle static scenes only. Our techniques mainly focus on the computation of indirect illumination, which is the most expensive part of global illumination modelling.Die Erstellung von hochqualitativen 3D-Animationen mit anspruchsvollen Lichteffekten ist für traditionelle Renderinganwendungen, bei denen jedes Bild separat berechnet wird, sehr aufwendig. Die Tatsache jedes Bild komplett neu zu berechnen führt zu unnötiger Redundanz. Wenn temporale Koherenz vernachlässigt wird, treten unter anderem auch schwierig zu behandelnde temporale Aliasingprobleme auf. Viele kleine Fehler in der Beleuchtungsberechnung eines Bildes können normalerweise nicht wahr genommen werden. Wenn jedoch die temporale Koherenz zwischen aufeinanderfolgenden Bildern fehlt, treten störende Flimmereffekte auf. In dieser Arbeit stellen wir globale Beleuchtungsalgorithmen vor, die die oben genannten Probleme behandeln. Dies erreichen wir durch Ausnutzung von temporaler Koherenz zwischen aufeinanderfolgenden Einzelbildern einer Animation. Unsere Strategy baut auf die klassischen globalen Beleuchtungsalgorithmen wie "Path tracing", "Photon Mapping" und "Irradiance Caching" auf und erweitert diese in die temporale Domäne. Dabei beschränken sich unsereMethoden hauptsächlich auf die Berechnung indirekter Beleuchtung, welche den zeitintensivsten Teil der globalen Beleuchtungsberechnung darstellt
Efficient global illumination for dynamic scenes
The production of high quality animations which feature compelling lighting effects is computationally a very heavy task when traditional rendering approaches are used where each frame is computed separately. The fact that most of the computation must be restarted from scratch for each frame leads to unnecessary redundancy. Since temporal coherence is typically not exploited, temporal aliasing problems are also more difficult to address. Many small errors in lighting distribution cannot be perceived by human observers when they are coherent in temporal domain. However, when such a coherence is lost, the resulting animations suffer from unpleasant flickering effects. In this thesis, we propose global illumination and rendering algorithms, which are designed specifically to combat those problems. We achieve this goal by exploiting temporal coherence in the lighting distribution between the subsequent animation frames. Our strategy relies on extending into temporal domain wellknown global illumination and rendering techniques such as density estimation path tracing, photon mapping, ray tracing, and irradiance caching, which have been originally designed to handle static scenes only. Our techniques mainly focus on the computation of indirect illumination, which is the most expensive part of global illumination modelling.Die Erstellung von hochqualitativen 3D-Animationen mit anspruchsvollen Lichteffekten ist für traditionelle Renderinganwendungen, bei denen jedes Bild separat berechnet wird, sehr aufwendig. Die Tatsache jedes Bild komplett neu zu berechnen führt zu unnötiger Redundanz. Wenn temporale Koherenz vernachlässigt wird, treten unter anderem auch schwierig zu behandelnde temporale Aliasingprobleme auf. Viele kleine Fehler in der Beleuchtungsberechnung eines Bildes können normalerweise nicht wahr genommen werden. Wenn jedoch die temporale Koherenz zwischen aufeinanderfolgenden Bildern fehlt, treten störende Flimmereffekte auf. In dieser Arbeit stellen wir globale Beleuchtungsalgorithmen vor, die die oben genannten Probleme behandeln. Dies erreichen wir durch Ausnutzung von temporaler Koherenz zwischen aufeinanderfolgenden Einzelbildern einer Animation. Unsere Strategy baut auf die klassischen globalen Beleuchtungsalgorithmen wie "Path tracing", "Photon Mapping" und "Irradiance Caching" auf und erweitert diese in die temporale Domäne. Dabei beschränken sich unsereMethoden hauptsächlich auf die Berechnung indirekter Beleuchtung, welche den zeitintensivsten Teil der globalen Beleuchtungsberechnung darstellt
Visibility-Based Optimizations for Image Synthesis
Katedra počítačové grafiky a interakce
Distributed visibility servers
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.Includes bibliographical references (leaves 54-55).This thesis describes techniques for computing conservative visibility exploiting viewpoint prediction, spatial coherence and remote visibility servers to increase the rendering performance of a walk through client. Identifying visible (or partially visible) geometry from an instantaneous viewpoint of a 3-D computer graphics model in real-time is an important problem in interactive computer graphics. Since rendering is an expensive process (due to transformations, lighting and scan-conversion), successfully identifying the exact set of visible geometry before rendering increases the frame-rate of real-time applications. However, computing this exact set is computationally intensive and prohibitive in real-time for large models. For many densely occluded environments that contain a small number of large occluding objects (such as buildings, billboards and houses), efficient conservative visibility algorithms have been developed to identify a set of occluded objects in real-time. These algorithms are conservative since they do not identify the exact set of occluded geometry. While visibility algorithms that identify occluded geometry are useful in increasing the frame-rate of interactive applications, previous techniques have not attempted to utilize a set of workstations connected via a local area network as an external compute resource. We demonstrated a configuration with one local viewer and two remote servers.by Eric A. Brittain.S.M
Visualization of urban environments
Ankara : The Department of Computer Engineering and the Institute of Engineering and Science of Bilkent University, 2007.Thesis (Ph. D.) -- Bilkent University, 2007.Includes bibliographical references leaves 108-118Modeling and visualization of large geometric environments is a popular research
area in computer graphics. In this dissertation, a framework for modeling and
stereoscopic visualization of large and complex urban environments is presented.
The occlusion culling and view-frustum culling is performed to eliminate most
of the geometry that do not contribute to the user’s final view. For the occlusion
culling process, the shrinking method is employed but performed using a
novel Minkowski-difference-based approach. In order to represent partial visibility,
a novel building representation method, called the slice-wise representation
is developed. This method is able to represent the preprocessed partial visibility
with huge reductions in the storage requirement. The resultant visibility list is
rendered using a graphics-processing-unit-based algorithm, which perfectly fits
into the proposed slice-wise representation. The stereoscopic visualization depends
on the calculated eye positions during walkthrough and the visibility lists
for both eyes are determined using the preprocessed occlusion information. The
view-frustum culling operation is performed once instead of two for both eyes.
The proposed algorithms were implemented on personal computers. Performance
experiments show that, the proposed occlusion culling method and the usage of
the slice-wise representation increase the frame rate performance by 81 %; the
graphics-processing-unit-based display algorithm increases it by an additional
315 % and decrease the storage requirement by 97 % as compared to occlusion
culling using building-level granularity and not using the graphics hardware. We
show that, a smooth and real-time visualization of large and complex urban environments
can be achieved by using the proposed framework.Yılmaz, TürkerPh.D
Object Hierarchies for Efficient Rendering
This thesis covers the efficient visualization of complex 3d scenes using various rendering methods such as photo-realistic and real-time rendering. Especially the important role of bounding volume hierarchies is discussed in detail in the context of illumination and visibility algorithms. We present a novel approach for automatic generation of object hierarchies and apply the resulting data structure to several rendering techniques. In the field of ray tracing we describe a novel ray acceleration method that combines objects hierarchies and regular grids. We demonstrate how radiosity computations may benefit from available scene hierarchies to determine the radiant flux between object clusters. Finally, we present an adaptive interactive rendering algorithm that may dramatically reduce the number of visibility tests in an occlusion culling framework for interactive real-time visualization.Diese Dissertation untersucht unterschiedliche Verfahren zur effizienten Visualisierung grosser dreidimensionaler Szenengeometrien, sowohl im Bereich des Photorealismus wie auch bei der Echtzeit-Visualisierung. Hierbei wird insbesondere die Nützlichkeit von Hüllkörperhierarchien bei der Beleuchtungsrechnung und bei der Beantwortung von Sichtbarkeitsfragen herausgearbeitet. Ein neuartiges, kostenbasiertes Verfahren zur automatischen Konstruktion von Objekthierarchien wird präsentiert sowie dessen Anwendung für alle gängigen Darstellungsverfahren. Zusätzlich beschreibt diese Disseration im Bereich Ray Tracing ein neues Verfahren zur Szenenstrukturierung, welches die Vorteile von Hüllkörperhierarchien und regulären Gittern kombiniert. Im Bereich der Radiosity wird gezeigt, wie sich Szenenhierarchien ideal zur Berechnung des Lichtflusses zwischen Objekt-Clustern nutzen lassen und im Bereich Echtzeit-Rendering wird ein adaptives Verfahren vorgestellt, dass die Zahl teurer Sichtbarkeitstests beim Occlusion-Culling deutlich reduziert
Large Model Visualization : Techniques and Applications
The size of datasets in scientific computing is rapidly
increasing. This increase is caused by a boost of processing power in
the past years, which in turn was invested in an increase of the
accuracy and the size of the models. A similar trend enabled a
significant improvement of medical scanners; more than 1000 slices of
a resolution of 512x512 can be generated by modern scanners in daily
practice. Even in computer-aided engineering typical models eas-ily
contain several million polygons. Unfortunately, the data complexity
is growing faster than the rendering performance of modern computer
systems. This is not only due to the slower growing graphics
performance of the graphics subsystems, but in particular because of
the significantly slower growing memory bandwidth for the transfer of
the geometry and image data from the main memory to the graphics
accelerator.
Large model visualization addresses this growing divide between data
complexity and rendering performance. Most methods focus on the
reduction of the geometric or pixel complexity, and hence also the
memory bandwidth requirements are reduced.
In this dissertation, we discuss new approaches from three different
research areas. All approaches target at the reduction of the
processing complexity to achieve an interactive visualization of large
datasets. In the second part, we introduce applications of the
presented ap-proaches. Specifically, we introduce the new VIVENDI
system for the interactive virtual endoscopy and other applications
from mechanical engineering, scientific computing, and architecture.The size of datasets in scientific computing is rapidly
increasing. This increase is caused by a boost of processing power in
the past years, which in turn was invested in an increase of the
accuracy and the size of the models. A similar trend enabled a
significant improvement of medical scanners; more than 1000 slices of
a resolution of 512x512 can be generated by modern scanners in daily
practice. Even in computer-aided engineering typical models eas-ily
contain several million polygons. Unfortunately, the data complexity
is growing faster than the rendering performance of modern computer
systems. This is not only due to the slower growing graphics
performance of the graphics subsystems, but in particular because of
the significantly slower growing memory bandwidth for the transfer of
the geometry and image data from the main memory to the graphics
accelerator.
Large model visualization addresses this growing divide between data
complexity and rendering performance. Most methods focus on the
reduction of the geometric or pixel complexity, and hence also the
memory bandwidth requirements are reduced.
In this dissertation, we discuss new approaches from three different
research areas. All approaches target at the reduction of the
processing complexity to achieve an interactive visualization of large
datasets. In the second part, we introduce applications of the
presented ap-proaches. Specifically, we introduce the new VIVENDI
system for the interactive virtual endoscopy and other applications
from mechanical engineering, scientific computing, and architecture
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