Rendering process of digital terrain model on mobile devices

Digital Terrain Model has been used in many applications especially in Geographical Information System. However with the recent improvement in mobile devices that can support 3 Dimension (3D) content, rendering 3D based terrain on mobile devices is possible. Although mobile devices have improved its capabilities, rendering 3D terrain is tedious due to the constraint in resources of mobile devices. Furthermore, rendering DTM add more constraint and issues to the mobile devices. This paper focuses on the rendering process of DTM on mobile devices to observe some issues and current constraints occurred. Also to determine the characteristic of terrain properties that will affect the rendering performance. Experiments were performed using five datasets that derived from aerial images. The experimental results are based on speed of rendering and the appearance of the terrain surface. From these results, issues and problems that are highlighted in this paper will be the focus of future research

Análise de Walkthroughts em Cenários 3D de um jogo utilizando Algoritmos de Visibilidade e Estruturas de Particionamento Espacial

Neste trabalho, apresentamos uma análise detalhada de walkthroughs em cenários 3D de um jogo digital, usando algoritmos de culling (View Frustum Culling e Backface Culling) e estruturas de particionamento espacial (Octree e BSP-Tree). Basicamente, focamos nossa análise nos seguintes aspectos principais: tempo de processamento total e por quadro gasto, redução eficaz de triângulos enviados ao pipeline de renderização de memória consumida

Point sample rendering

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1998.Includes bibliographical references (p. 54-56).We present an algorithm suitable for real-time, high quality rendering of complex objects. Objects are represented as a dense set of surface point samples which contain colour, depth and normal information. These point samples are obtained by sampling orthographic views on an equilateral triangle lattice. They are rendered directly and independently without any knowledge of surface topology. We introduce a novel solution to the problem of surface reconstruction using a hierarchy of Z-buffers to detect tears. The algorithm is fast, easily vectorizable, and requires only modest resources.by J.P. Grossman.S.M

Accelerating Virtual Walkthrough with Visual Culling Techniques

Abstract-Virtual walkthrough application allows users to navigate and immerse in the generated 3D environment with computer graphics assist. The 3D environment requires a large amount of geometry to make it look realistic. When the number of geometry increase, the performance of the application will become slower. Consequently, it creates a conflict between the needs of realistic and real time. In this paper, we discuss the implementation of visual culling techniques such as view frustum culling, back face culling and occlusion culling in the virtual walkthrough application. We render only what we can see during the application runtime and cull away unnecessary geometry. This will accelerate the performance of the system. Without the culling techniques implemented in virtual reality application such as virtual walkthrough, the system has to allocate a large space of memory to store the geometry data. We have tested these techniques to the Ancient Malacca data. With the visual culling techniques implemented, the virtual walkthrough system can work in real time mode without scarifying realism factor

Flexible occlusion rendering for improved views of three-dimensional medical images

The goal of this work is to enable more rapid and accurate diagnosis of pathology from three-dimensional (3D) medical images by augmenting standard volume rendering techniques to display otherwise-occluded features within the volume. When displaying such data sets with volume rendering, appropriate selection of the transfer function is critical for determining which features of the data will be displayed. In many cases, however, no transfer function is able to produce the most useful views for diagnosis of pathology. Flexible Occlusion Rendering (FOR) is an addition to standard ray cast volume rendering that modulates accumulated color and opacity along each ray upon detecting features indicating the separation between objects of the same intensity range. For contrast-enhanced MRI and CT data, these separation features are intensity peaks. To detect these peaks, a dual-threshold method is used to reduce sensitivity to noise. To further reduce noise and enable control over the spatial scale of the features detected, a smoothed version of the original data set is used for feature detection, while rendering the original data at high resolution. Separating the occlusion feature detection from the volume rendering transfer function enables robust occlusion determination and seamless transition from occluded views to non-occluded views of surfaces during virtual fly-throughs. FOR has been applied to virtual arthroscopy of joints from MRI data. For example, survey views of entire shoulder socket surfaces have been rendered to enable rapid evaluation by automatically removing the occluding material of the humeral head. Such views are not possible with standard volume rendering. FOR has also been successfully applied to virtual ureteroscopy of the renal collecting system from CT data, and knee fracture visualization from CT data

View space linking, solid node compression and binary space partitioning for visibility determination in 3D walk-throughs

Today\u27s 3D games consumers are expecting more and more quality in their games. To enable high quality graphics at interactive rates, games programmers employ a technique known as hidden surface removal (HSR) or polygon culling. HSR is not just applicable to games; it may also be applied to any application that requires quality and interactive rates, including medical, military and building applications. One such commonly used technique for HSR is the binary space partition (BSP) tree, which is used for 3D ‘walk-throughs’, otherwise known as 3D static environments or first person shooters. Recent developments in 3D accelerated hardware technology do not mean that HSR is becoming redundant; in fact, HSR is increasingly becoming more important to the graphics pipeline. The well established potentially visible sets (PSV) BSP tree algorithm is used as a platform for exploring three enhanced algorithms; View Space Lighting, Solid Node Compression and hardware accelerated occlusion are shown to reducing the amounts of nodes that are traversed in a BSP tree, improving tree travel efficiency. These algorithms are proven (in cases) to improve overall efficiency

Visualización progresiva de redes tetraédricas en el dominio de wavelet

La transmisión progresiva de redes tetraédricas en el dominio wavelet es muy eficiente. Sólo es necesario transmitir primero la red base junto con los coeficientes obtenidos durante el análisis multirresolución, mientras que los detalles pueden ser transmitidos después, por paquetes y en desorden. En este trabajo proponemos un algoritmo simple y robusto para visualización progresiva de tales redes tetraédricas. Adaptamos la red en tiempo de ejecución para mostrar el máximo detalle posible mediante un esquema de refinamiento rojo/verde al tiempo que aumentamos la eficiencia del rendering reduciendo el detalle en las zonas no visibles con respecto al punto de vista.Currently, the progressive transmission of tetrahedral meshes in the wavelet domain is very efficient. It is necessary to pass on first the base mesh along with the coefficient obtained during the multi resolution analysis before transmitting the details. The details can be transmitted in packages without a specific order. In this paper we suggest a simple but strong algorithm for progressive visualization of tetrahedral meshes in the wavelet domain. We adjust the mesh during the execution time using the red/green refinement technique in order to show all the possible details. At the same time, we improve the volume renderer performance by reducing its work load in all the non visible parts with regard to the point of view.Red de Universidades con Carreras en Informática (RedUNCI

Visualización progresiva de redes tetraédricas en el dominio de wavelet

La transmisión progresiva de redes tetraédricas en el dominio wavelet es muy eficiente. Sólo es necesario transmitir primero la red base junto con los coeficientes obtenidos durante el análisis multirresolución, mientras que los detalles pueden ser transmitidos después, por paquetes y en desorden. En este trabajo proponemos un algoritmo simple y robusto para visualización progresiva de tales redes tetraédricas. Adaptamos la red en tiempo de ejecución para mostrar el máximo detalle posible mediante un esquema de refinamiento rojo/verde al tiempo que aumentamos la eficiencia del rendering reduciendo el detalle en las zonas no visibles con respecto al punto de vista.Currently, the progressive transmission of tetrahedral meshes in the wavelet domain is very efficient. It is necessary to pass on first the base mesh along with the coefficient obtained during the multi resolution analysis before transmitting the details. The details can be transmitted in packages without a specific order. In this paper we suggest a simple but strong algorithm for progressive visualization of tetrahedral meshes in the wavelet domain. We adjust the mesh during the execution time using the red/green refinement technique in order to show all the possible details. At the same time, we improve the volume renderer performance by reducing its work load in all the non visible parts with regard to the point of view.Red de Universidades con Carreras en Informática (RedUNCI

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