27-Issue 1

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https://diglib.eg.org/handle/10.2312/134

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    A General Multi-step Algorithm for Voxel Traversing Along a Line
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Liu, Y. K.; Song, H. Y.; Zalik, B.
    Traversing voxels along a three dimensional (3D) line is one of the most fundamental algorithms for voxel-based applications. This paper presents a new 6-connectivity integer algorithm for this task. The proposed algorithm accepts voxels having different sizes in x, y and z directions. To explain the idea of the proposed approach, a 2D algorithm is firstly considered and then extended in 3D. This algorithm is a multi-step as up to three voxels may be added in one iteration. It accepts both integer and floating-point input.The new algorithm was compared to other popular voxel traversing algorithms. Counting the number of arithmetic operations showed that the proposed algorithm requires the least amount of operations per traversed voxel. A comparison of spent CPU time using either integer or floating-point arithmetic confirms that the proposed algorithm is the most efficient. This algorithm is simple, and in compact form which also makes it attractive for hardware implementation.
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    Point-Based Rendering of Non-Manifold Surfaces
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Balsys, Ron J.; Suffern, K. G.; Jones, Huw
    We are concerned with producing high-quality images of parametric and implicit surfaces, in particular those with non-manifold features. We present a point-based technique for rendering implicit surfaces that uses octree spatial subdivision with a natural interval exclusion test that guarantees that no parts of the surface are missed. This allows us to render non-manifold implicit surfaces at speeds comparable to parametric surfaces. We also derive criteria that guarantee complete pixel coverage of the surface. The point-based method allows for hidden surface elimination using a z-buffer, and shadow casting using a shadow buffer. We illustrate the technique with a number of surfaces, and discuss its advantages and disadvantages.
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    A Flexible Kernel for Adaptive Mesh Refinement on GPU
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Boubekeur, T.; Schlick, C.
    We present a flexible GPU kernel for adaptive on-the-fly refinement of meshes with arbitrary topology. By simply reserving a small amount of GPU memory to store a set of adaptive refinement patterns, on-the-fly refinement is performed by the GPU, without any preprocessing nor additional topology data structure. The level of adaptive refinement can be controlled by specifying a per-vertex depth-tag, in addition to usual position, normal, color and texture coordinates. This depth-tag is used by the kernel to instanciate the correct refinement pattern, which will map a refined connectivity on the input coarse polygon. Finally, the refined patch produced for each triangle can be displaced by the vertex shader, using any kind of geometric refinement, such as Bezier patch smoothing, scalar valued displacement, procedural geometry synthesis or subdivision surfaces. This refinement engine does neither require multipass rendering nor any use of fragment processing nor special preprocess of the input mesh structure. It can be implemented on any GPU with vertex shading capabilities.
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    Table of Contents, Cover
    (The Eurographics Association and Blackwell Publishing Ltd, 2008)
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    A Comparison of Methods for Generating Poisson Disk Distributions
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Lagae, Ares; Dutre, Philip
    Poisson disk distributions have many applications in the field of computer graphics. Besides sampling, Poisson disk distributions are used in object distribution, non-photorealistic rendering and procedural texturing. Over the years, a large number of methods for generating Poisson disk distributions have been proposed, making it difficult to choose the right method for a given application. In this paper, we present a detailed comparison of most techniques for generating Poisson disk distributions. The methods we study include dart throwing, relaxation dart throwing, Lloyd s relaxation, Shade s Poisson disk tiles, tiled blue noise samples, fast hierarchical importance sampling with blue noise properties, edge-based Poisson disk tiles, template Poisson disk tiles, corner-based Poisson disk tiles and recursive Wang tiles for real-time blue noise. Analysing all of these methods within a single framework is one of the major contributions of this work.
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    Volume and Isosurface Rendering with GPU-Accelerated Cell Projection*
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Marroquim, R.; Maximo, A.; Farias, R.; Esperanca, C.
    We present an efficient Graphics Processing Unit GPU-based implementation of the Projected Tetrahedra (PT) algorithm. By reducing most of the CPU-GPU data transfer, the algorithm achieves interactive frame rates (up to 2.0 M Tets/s) on current graphics hardware. Since no topology information is stored, it requires substantially less memory than recent interactive ray casting approaches. The method uses a two-pass GPU approach with two fragment shaders. This work includes extended volume inspection capabilities by supporting interactive transfer function editing and isosurface highlighting using a Phong illumination model.
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    A Sketch-Based User Interface for Reconstructing Architectural Drawings
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Lee, Sangwon; Feng, David; Grimm, Cindy; Gooch, Bruce
    We present a framework for interactive sketching that allows users to create three-dimensional (3D) architectural models quickly and easily from a source drawing. The sketching process has four steps. (1) The user calibrates a viewing camera by specifying the origin and vanishing points of the drawing. (2) The user outlines surface polygons in the drawing. (3) A 3D reconstruction algorithm uses perceptual constraints to determine the closest visual fit for the polygon. (4) The user can then adjust aesthetic controls to produce several stylistic effects in the scene: a smooth transition between day and night rendering, a horizon knockout effect and entourage figures. The major advantage of our approach lies in the combination of perception-based techniques, which allow us to minimize unnecessary interactions, and a hinging-angle scheme, which shows significant improvement in numerical stability over previous optimization-based 3D reconstruction algorithms. We also demonstrate how our reconstruction algorithm can be extended to work with perspective images, a feature unavailable in previous approaches.
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    Real-Time GPU Silhouette Refinement using Adaptively Blended Bezier Patches
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Dyken, C.; Reimers, M.; Seland, J.
    We present an algorithm for detecting and extracting the silhouette edges of a triangle mesh in real time using Graphical Processing Units (GPUs). We also propose a tessellation strategy for visualizing the mesh with smooth silhouettes through a continuous blend between Bezier patches with varying level of detail. Furthermore, we show how our techniques can be integrated with displacement and normal mapping. We give details on our GPU implementation and provide a performance analysis with respect to mesh size.
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    CGForum 2008 Cover Image
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Mezger, Johannes; Thomaszewski, Bernhard; Pabst, Simon; Strasser, Wolfgang
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    Distributed Texture Memory in a Multi-GPU Environment
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Moerschell, Adam; Owens, John D.
    In this work, we demonstrate a system that allows texture memory on multiple graphics processing unit (GPUs) to be virtualized in a manner that is both scalable and transparent to the programmer. Our system is built using a directory-based shared-memory abstraction to allow texture memory to be distributed while staying consistent. We use texture pages as our basic memory block and discuss the data structures, threading model, and consistency mechanisms necessary to implement a paging system in a multi-GPU environment. The system is demand-driven, and pages will only be loaded into the texture memory of a GPU that makes a request. The main contribution of this work is the identification of the mechanisms required to implement our abstraction, as well as the discussion of its limitations in order to make it more efficient.
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    Pressing: Smooth Isosurfaces with Flats from Binary Grids
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Chica, A.; Williams, J.; Andujar, C.; Brunet, P.; Navazo, I.; Rossignac, J.; Vinacua, A.
    We explore the automatic recovery of solids from their binary volumetric discretizations. In particular, we propose an approach, called Pressing, for smoothing isosurfaces extracted from binary volumes while recovering their large planar regions (flats). Pressing yields a surface that is guaranteed to contain the samples of the volume classified as interior and exclude those classified as exterior. It uses global optimization to identify flats and constrained bilaplacian smoothing to eliminate sharp features and high frequencies from the rest of the isosurface. It recovers sharp edges between flat regions and between flat and smooth regions. Hence, the resulting isosurface is usually a very accurate approximation of the original solid. Furthermore, the segmentation of the isosurface into flat and curved faces and the sharp/smooth labelling of their edges may be valuable for shape recognition, simplification, compression and various reverse engineering and manufacturing applications.
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    Object-Space Visibility Ordering for Point-Based and Volume Rendering
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Hofsetz, C.; Max, N.; Bastos, R.
    This paper presents a method to accelerate algorithms that need a correct and complete visibility ordering of their data for rendering. The technique works by pre-sorting primitives in object-space using three lists (one for each axis: X, Y and Z), and then combining the lists using graphics hardware by rendering each list to a texture and merging the textures in the end. We validate our algorithm by applying it to the splatting technique using several types of rendering, including point-based rendering and volume rendering. We also detail our hardware implementation for volume rendering using point sprites.
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    Occlusion Textures for Plausible Soft Shadows*
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Eisemann, E.; Decoret, X.
    This paper presents a new approach to compute plausible soft shadows for complex dynamic scenes and rectangular light sources. We estimate the occlusion at each point of the scene using prefiltered occlusion textures, which dynamically approximate the scene geometry. The algorithm is fast and its performance independent of the light s size. Being image-based, it is mostly independent of the scene complexity and type. No a priori information is needed, and there is no caster/receiver separation. This makes the method appealing and easy to use.
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    A Dynamic Model of Cracks Development Based on a 3D Discrete Shrinkage Volume Propagation
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Valette, Gilles; Prevost, Stephanie; Lucas, Laurent; Leonard, Joel
    We attempt to model and visualize the main characteristics of cracks produced on the surface of a desiccating crusted soil: their patterns, their different widths and depths and their dynamics of creation and evolution. In this purpose we propose a method to dynamically produce three-dimensional (3D) quasi-static fractures, which takes into account the characteristics of the soil. The main originality of this method is the use of a 3D discrete propagation of shrinkage volumes with respect to 2D precalculated paths. In order to get realistic cracks, we newly propose to take into account a possibly inhomogeneous thickness of the shrinking layer by using a watershed transformation to compute these paths. Moreover, we use the waterfall algorithm in order to introduce in our simulation a hierarchy notion in the cracks appearance, which is therefore linked with the initial structure of the surface. In this paper, this method is presented in detail and a validation of the cracks patterns by a comparison with real ones is given.