Recently, methods were developed to render various global illumination effects with rasterization GPUs. Among those were hardware based ray tracing and photon mapping. However, due to current GPU??s inherent architectural limitations, the efficiency and throughput of these methods remained low. In this thesis, we propose a coherent rendering system that addresses these issues. First, we introduce new photon mapping and ray racing acceleration algorithms that facilitate data coherence and spatial locality, as well as eliminating unnecessary random memory accesses. A high level abstraction of the combined ray tracing and photon mapping streaming pipeline is introduced. Based on this abstraction, an efficient ray tracing and photon mapping GPU is designed. Using an event driven simulator, developed for this GPU, we verify and validate the proposed algorithms and architecture. Simulation results have validated better interactive performances compared to the current GPUs.

The influence of elastic anisotropy on seismic wave propagation is often neglected for the sake of simplicity. However, ignoring anisotropy may lead to significant errors in the processing of seismic data and ultimately in a poor image of the subsurface. This is especially true in wide-aperture Vertical Seismic Profiles where waves travel both vertically and horizontally. Anisotropy has been neglected in wavefront construction methods of seismic ray-tracing until Gibson (2000), who showed they are powerful tools to simulate seismic wave propagation in three-dimensional anisotropic subsurface models. The code is currently under development using a C++ object oriented programming approach because it provides high flexibility in the design of new components and facilitates debugging and maintenance of a complex algorithm. So far, the code was used to simulate propagation in homogeneous or simple heterogeneous anisotropic velocity models mainly designed for testing purposes. In particular, it has never been applied to simulate a field dataset. We propose here an analytical method involving little algebra and that allows the design of realistic heterogeneous anisotropic models using the C++ object oriented programming approach. The new model class can model smooth multi-layered subsurface with gradients or models with many dip variations. It has been used to model first arrival times of a wide-aperture VSP dataset from the Gulf of Mexico to estimate the amount of anisotropy. The proposed velocity model is transversely isotropic. The anisotropy is constant throughout the model and is defined via Thomsen's parameters. Values in the final model are epsilon = 0.055 and delta = -0.115. The model is compatible with the a priori knowledge of the local geology and reduces the RMS average time difference between measured and computed travel times by 51% in comparison to the initial isotropic model. These values are realistic and are similar to other measurements of anisotropy in the Gulf of Mexico.

In the past, ray tracing has been used widely in offline rendering applications since it provided the ability to better capture high quality secondary effects such as reflection, refraction and shadows. Such effects are difficult to produce in a robust, high quality fashion with traditional, real-time rasterization algorithms. Motivated to bring the advantages to ray tracing to real-time applications, researchers have developed better and more efficient algorithms that leverage the current generation of fast, parallel CPU hardware within the past few years. This thesis provides the implementation and design details of a high performance ray tracing solution called ``RTTest'' for standard, desktop CPUs. Background information on various algorithms and acceleration structures are first discussed followed by an introduction to novel techniques used to better accelerate current, core ray tracing techniques. Techniques such as Omni-Directional Packets, Cone Proxy Traversal and Multiple Frustum Traversal are proposed and benchmarked using standard ray tracing scenes. Also, a novel soft shadowing algorithm called Edge Width Soft Shadows is proposed which achieves performance comparable to a single sampled hard shadow approach targeted at real time applications such as games. Finally, additional information on the memory layout, rendering pipeline, shader system and code level optimizations of RTTest are also discussed.

CAD objects are geometrical descriptions of physical scenes from the real world. Ray tracing is used to project the objects onto a pixel screen. A lit and a shadow zone are formed according to the direction of the incoming field (light) and the orientation of the pixel screen. The arc length along the surface of the object, from the shadow boundary to a point in the lit zone, is computed by means of numerical integration. The arclengths corresponding to two orthogonal directions that are aligned with the pixels on the pixel screen are computed and used for interpolation to obtain the arc length for all directions. A number of simulations for various CAD geometries are made using a ray-tracer implemented in FORTRAN 90.

In the past, ray tracing has been used widely in offline rendering applications since it provided the ability to better capture high quality secondary effects such as reflection, refraction and shadows. Such effects are difficult to produce in a robust, high quality fashion with traditional, real-time rasterization algorithms. Motivated to bring the advantages to ray tracing to real-time applications, researchers have developed better and more efficient algorithms that leverage the current generation of fast, parallel CPU hardware within the past few years. This thesis provides the implementation and design details of a high performance ray tracing solution called ``RTTest'' for standard, desktop CPUs. Background information on various algorithms and acceleration structures are first discussed followed by an introduction to novel techniques used to better accelerate current, core ray tracing techniques. Techniques such as Omni-Directional Packets, Cone Proxy Traversal and Multiple Frustum Traversal are proposed and benchmarked using standard ray tracing scenes. Also, a novel soft shadowing algorithm called Edge Width Soft Shadows is proposed which achieves performance comparable to a single sampled hard shadow approach targeted at real time applications such as games. Finally, additional information on the memory layout, rendering pipeline, shader system and code level optimizations of RTTest are also discussed.

The influence of elastic anisotropy on seismic wave propagation is often neglected for the sake of simplicity. However, ignoring anisotropy may lead to significant errors in the processing of seismic data and ultimately in a poor image of the subsurface. This is especially true in wide-aperture Vertical Seismic Profiles where waves travel both vertically and horizontally. Anisotropy has been neglected in wavefront construction methods of seismic ray-tracing until Gibson (2000), who showed they are powerful tools to simulate seismic wave propagation in three-dimensional anisotropic subsurface models. The code is currently under development using a C++ object oriented programming approach because it provides high flexibility in the design of new components and facilitates debugging and maintenance of a complex algorithm. So far, the code was used to simulate propagation in homogeneous or simple heterogeneous anisotropic velocity models mainly designed for testing purposes. In particular, it has never been applied to simulate a field dataset. We propose here an analytical method involving little algebra and that allows the design of realistic heterogeneous anisotropic models using the C++ object oriented programming approach. The new model class can model smooth multi-layered subsurface with gradients or models with many dip variations. It has been used to model first arrival times of a wide-aperture VSP dataset from the Gulf of Mexico to estimate the amount of anisotropy. The proposed velocity model is transversely isotropic. The anisotropy is constant throughout the model and is defined via Thomsen's parameters. Values in the final model are epsilon = 0.055 and delta = -0.115. The model is compatible with the a priori knowledge of the local geology and reduces the RMS average time difference between measured and computed travel times by 51% in comparison to the initial isotropic model. These values are realistic and are similar to other measurements of anisotropy in the Gulf of Mexico.

Recently, methods were developed to render various global illumination effects with rasterization GPUs. Among those were hardware based ray tracing and photon mapping. However, due to current GPU??s inherent architectural limitations, the efficiency and throughput of these methods remained low. In this thesis, we propose a coherent rendering system that addresses these issues. First, we introduce new photon mapping and ray racing acceleration algorithms that facilitate data coherence and spatial locality, as well as eliminating unnecessary random memory accesses. A high level abstraction of the combined ray tracing and photon mapping streaming pipeline is introduced. Based on this abstraction, an efficient ray tracing and photon mapping GPU is designed. Using an event driven simulator, developed for this GPU, we verify and validate the proposed algorithms and architecture. Simulation results have validated better interactive performances compared to the current GPUs.

Observing seafloor crustal deformation is often composed of acoustic ranging and GPS positioning techniques, which involves positioning of a single seabed transponder. Generally, the positional uncertainty of the seabed transponder is evaluated in terms of the slant range residuals. In order to further verify the relative positioning accuracy between seabed transponders, this study designed and fabricated a transponder lander. Three transponders were mounted on the lander to form a triangle with sides 1.505, 1.505 and 1.160 m. In addition, a data acquisition and logging system is developed to collect the lander¡¦s attitude, including pitch, roll, heading, and accelerations in three orthogonal axes. A field experiment to verify the relative positioning accuracy between seabed transponders was carried out off the coast of Kaohsiung Harbor, Taiwan. The transponder lander was deployed on the seabed at a water depth of about 300 m. Based on the attitude data collected by the logging system, the heading, pitch and roll of the transponder lander on the seabed are 123.5 degrees, 0.63 degrees and 0.62 degrees, respectively. A vessel was sailed along predetermined paths to collect observations of GPS and acoustic slant range. Then, an optimization technique combined with ray tracing method was used to estimate the positions of three transponders. The position estimates of the three transponders form a triangle with sides 1.533, 1.518 and 1.184 m, which shows that, comparing with the true values, the relative positioning error between transponders is less than 3 cm. Furthermore, based on the estimates of the transponder positions, the heading, pitch and roll of the transponder lander are calculated as 120.45 degrees, 6.43 degrees and 2.51 degrees, respectively, which are in good agreement with that measured by the attitude logging system. The experimental and evaluation results indicate that the optimization technique along with the ray tracing method is practical for precisely estimating the transponder position.

Zugl.: Koblenz, Landau (Pfalz), Univ., Diss., 2008

Thesis (M.S.)--Ohio University, November, 2009. / Title from PDF t.p. Includes bibliographical references.