Methods for Automated Creation and Efficient Visualisation of Large-Scale Terrains based on Real Height-Map Data

Real-time rendering of large-scale terrains is a difficult problem and remains an active field of research. The massive scale of these landscapes, where the ratio between the size of the terrain and its resolution is spanning multiple orders of magnitude, requires an efficient level of detail strategy. It is crucial that the geometry, as well as the terrain data, are represented seamlessly at varying distances while maintaining a constant visual quality. This thesis investigates common techniques and previous solutions to problems associated with the rendering of height field terrains and discusses their benefits and drawbacks. Subsequently, two solutions to the stated problems are presented, which build and expand upon the state-of-the-art rendering methods. A seamless and efficient mesh representation is achieved by the novel Uniform Distance-Dependent Level of Detail (UDLOD) triangulation method. This fully GPU-based algorithm subdivides a quadtree covering the terrain into small tiles, which can be culled in parallel, and are morphed seamlessly in the vertex shader, resulting in a densely and temporally consistent triangulated mesh. The proposed Chunked Clipmap combines the strengths of both quadtrees and clipmaps to enable efficient out-of-core paging of terrain data. This data structure allows for constant time view-dependent access, graceful degradation if data is unavailable, and supports trilinear and anisotropic filtering. Together these, otherwise independent, techniques enable the rendering of large-scale real-world terrains, which is demonstrated on a dataset encompassing the entire Free State of Saxony at a resolution of one meter, in real-time

Breaking the 64 spatialized sources barrier

International audienceSpatialized soundtracks and sound-effects are standard elements of today's video games. However, although 3D audio modeling and content creation tools (e.g., Creative Lab's EAGLE [4]) provide some help to game audio designers, the number of available 3D audio hardware channels remains limited, usually ranging from 16 to 64 in the best case. While one can wonder whether more hardware channels are actually required, it is clear that large numbers of spatialized sources might be needed to render a realistic environment. This problem becomes even more significant if extended sound sources are to be simulated: think of a train for instance, which is far too long to represented as a point source. Since current hardware and APIs implement only point-source models or limited extended source models [2,3,5], a large number of such sources would be required to achieve a realistic effect (view Example1). Finally, 3D-audio channels might also be used for restitution-independent representation of surround music tracks, leaving the generation of the final mix to the audio rendering API but requiring the programmer to assign some of the precious 3D channels to the soundtrack. Also, dynamic allocation schemes currently available in game APIs (e.g. Direct Sound 3D [2]) remain very basic. As a result, game audio designers and developers have to spend a lot of effort to best-map the potentially large number of sources to the limited number of channels. In this paper, we provide some answers to this problem by reviewing and introducing several automatic techniques to achieve efficient hardware mapping of complex dynamic audio scenes in the context of currently available hardware resources

Conservative From-Point Visibility.

Visibility determination has been an important part of the computer graphics research for several decades. First studies of the visibility were hidden line removal algorithms, and later hidden surface removal algorithms. Today’s visibility determination is mainly concentrated on conservative, object level visibility determination techniques. Conservative methods are used to accelerate the rendering process when some exact visibility determination algorithm is present. The Z-buffer is a typical exact visibility determination algorithm. The Z-buffer algorithm is implemented in practically every modern graphics chip. This thesis concentrates on a subset of conservative visibility determination techniques. These techniques are sometimes called from-point visibility algorithms. They attempt to estimate a set of visible objects as seen from the current viewpoint. These techniques are typically used with real-time graphics applications such as games and virtual environments. Concentration is on the view frustum culling and occlusion culling. View frustum culling discards objects that are outside of the viewable volume. Occlusion culling algorithms try to identify objects that are not visible because they are behind some other objects. Also spatial data structures behind the efficient implementations of view frustum culling and occlusion culling are reviewed. Spatial data structure techniques like maintaining of dynamic scenes and exploiting spatial and temporal coherences are reviewed.1. Introduction.............................................................................................................1 2. Visibility Problem...................................................................................................3 3. Scene Organization...............................................................................................10 3.1. Bounding Volume Hierarchies and Scene Graphs.................................10 3.2. Spatial Data Structures ...............................................................................13 3.3. Regular Grids...............................................................................................14 3.4. Quadtrees and Octrees ...............................................................................15 3.5. KD-Trees.......................................................................................................20 3.6. BSP-Trees......................................................................................................23 3.7. Exploiting Spatial and Temporal Coherence ..........................................27 3.8. Dynamic Scenes...........................................................................................30 3.9. Summary ......................................................................................................34 4. View Frustum Culling .........................................................................................35 4.1. View Frustum Construction ......................................................................36 4.2. View Frustum Test......................................................................................37 4.3. Hierarchical View Frustum Culling .........................................................41 4.4. Optimizations ..............................................................................................42 4.5. Summary ......................................................................................................44 5. Occlusion Culling .................................................................................................45 5.1. Fundamental Concepts...............................................................................45 5.2. Occluder Selection.......................................................................................46 5.3. Hardware Occlusion Queries....................................................................49 5.4. Object-Space Methods ................................................................................50 5.5. Image-Space Methods ................................................................................55 5.6. Summary ......................................................................................................64 6. Conclusion.............................................................................................................66 References .................................................................................................................... 7

Fast Ray Tracing Techniques

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

Simulation Of Virtual Reality Display Characteristics: A Method For The Evaluation Of Motion Perception

Visual perception in virtual reality devices is a widely researched topic. Many newer experiments compare their results to those of older studies that may have used equipment which is now outdated, which can cause perceptual differences. These differences in hardware can be simulated to a degree in software, provided the capabilities of the current hardware meet or exceed those of the older hardware. I present the HMD Simulation Framework, a software package for the Unity3D engine that allows for quick modification of many commonly researched HMD characteristics through the Inspector GUI built into Unity. I also describe a human subjects experiment aimed at identifying perceptual equivalence classes between different sets of headset characteristics. Unfortunately, due to the COVID-19 pandemic, all human subjects research was suspended for safety reasons, and I was unable to collect any data

Efficient shadow algorithms on graphics hardware

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2005.Includes bibliographical references (p. 85-92).Shadows are important to computer graphics because they add realism and help the viewer identify spatial relationships. Shadows are also useful story-telling devices. For instance, artists carefully choose the shape, softness, and placement of shadows to establish mood or character. Many shadow generation techniques developed over the years have been used successfully in offline movie production. It is still challenging, however, to compute high-quality shadows in real-time for dynamic scenes. This thesis presents two efficient shadow algorithms. Although these algorithms are designed to run in real-time on graphics hardware, they are also well-suited to offline rendering systems. First, we describe a hybrid algorithm for rendering hard shadows accurately and efficiently. Our method combines the strengths of two existing techniques, shadow maps and shadow volumes. We first use a shadow map to identify the pixels in the image that lie near shadow discontinuities. Then, we perform the shadow-volume computation only at these pixels to ensure accurate shadow edges. This approach simultaneously avoids the edge aliasing artifacts of standard shadow maps and avoids the high fillrate consumption of standard shadow volumes. The algorithm relies on a hardware mechanism that we call a computation mask for rapidly rejecting non-silhouette pixels during rasterization. Second, we present a method for the real-time rendering of soft shadows. Our approach builds on the shadow map algorithm by attaching geometric primitives that we call smoothies to the objects' silhouettes. The smoothies give rise to fake shadows that appear qualitatively like soft shadows, without the cost of densely sampling an area light source.(cont.) In particular, the softness of the shadow edges depends on the ratio of distances between the light source, the blockers, and the receivers. The soft shadow edges hide objectionable aliasing artifacts that are noticeable with ordinary shadow maps. Our algorithm computes shadows efficiently in image space and maps well to programmable graphics hardware.by Eric Chan.S.M

Efficient From-Point Visibility for Global Illumination in Virtual Scenes with Participating Media

Sichtbarkeitsbestimmung ist einer der fundamentalen Bausteine fotorealistischer Bildsynthese. Da die Berechnung der Sichtbarkeit allerdings äußerst kostspielig zu berechnen ist, wird nahezu die gesamte Berechnungszeit darauf verwendet. In dieser Arbeit stellen wir neue Methoden zur Speicherung, Berechnung und Approximation von Sichtbarkeit in Szenen mit streuenden Medien vor, die die Berechnung erheblich beschleunigen, dabei trotzdem qualitativ hochwertige und artefaktfreie Ergebnisse liefern