Issue 3

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https://diglib.eg.org/handle/10.2312/111

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Now showing 1 - 20 of 49

Precise Ink Drawing of 3D Models
(Blackwell Publishers, Inc and the Eurographics Association, 2003) Sousa, Mario Costa; Foster, Kevin; Wyvill, Brian; Samavati, Faramarz
Drawings made with precise pen strokes accurately reveal the geometric forms that give subjects their characteristicshape. We present a system for non-photorealistic rendering of precise drawing strokes over dense 3Dtriangle meshes with arbitrary topology. During an automatic pre-process, we construct an extended version ofthe edge-buffer data structure to allow the calculation of shape measures at each mesh edge, by adapting numericalmethods used in geomorphology. At runtime, feature edges related to shape measures are extracted andrendered as strokes with varying thickness and pen marking styles. Stroke thickness is automatically adjusted byconsidering surface curvature. Pen marking styles and visual effects of ink distribution are both controlled by theuser. We demonstrate precise drawing strokes over complex meshes revealing a variety of shape characteristics.
Cloth Motion Capture
(Blackwell Publishers, Inc and the Eurographics Association, 2003) Pritchard, D.; Heidrich, W.
Recent years have seen an increased interest in motion capture systems. Current systems, however, are limitedto only a few degrees of freedom, so that effectively only the motion of linked rigid bodies can be acquired. Wepresent a system for the capture of deformable surfaces, most notably moving cloth, including both geometry andparameterisation. We recover geometry using stereo correspondence, and use the Scale Invariant Feature Transform(SIFT) to identify an arbitrary pattern printed on the cloth, even in the presence of fast motion. We describea novel seed-and-grow approach to adapt the SIFT algorithm to deformable geometry. Finally, we interpolatefeature points to parameterise the complete geometry.Categories and Subject Descriptors (according to ACM CCS): I.3.5 [Computer Graphics]: Physically based modelingI.4.8 [Image Processing and Computer Vision]: Scene analysis
Multi-scale Feature Extraction on Point-Sampled Surfaces
(Blackwell Publishers, Inc and the Eurographics Association, 2003) Pauly, Mark; Keiser, Richard; Gross, Markus
We present a new technique for extracting line-type features on point-sampled geometry. Given an unstructuredpoint cloud as input, our method first applies principal component analysis on local neighborhoods toclassify points according to the likelihood that they belong to a feature. Using hysteresis thresholding, we thencompute a minimum spanning graph as an initial approximation of the feature lines. To smooth out the featureswhile maintaining a close connection to the underlying surface, we use an adaptation of active contour models.Central to our method is a multi-scale classification operator that allows feature analysis at multiplescales, using the size of the local neighborhoods as a discrete scale parameter. This significantly improves thereliability of the detection phase and makes our method more robust in the presence of noise. To illustrate theusefulness of our method, we have implemented a non-photorealistic point renderer to visualize point-sampledsurfaces as line drawings of their extracted feature curves.
Interactive Design of Bonsai Tree Models
(Blackwell Publishers, Inc and the Eurographics Association, 2003) Boudon, Frederic; Prusinkiewicz, Przemyslaw; Federl, Pavol; Godin, Christophe; Karwowski, Radoslaw
Because of their complexity, plant models used in computer graphics are commonly created with proceduralmethods. A difficult problem is the user control of these models: a small number of parameters is insufficient tospecify plant characteristics in detail, while large numbers of parameters are tedious to manipulate and difficultto comprehend. To address this problem, we propose a method for managing parameters involved in plant modelmanipulation. Specifically, we introduce decomposition graphs as multiscale representations of plant structuresand present interactive tools for designing trees that operate on decomposition graphs. The supported operationsinclude browsing of the parameter space, editing of generalized parameters (scalars, functions, and branchingsystem silhouettes), and the definition of dependencies between parameters. We illustrate our method by creatingmodels of bonsai trees.Categories and Subject Descriptors (according to ACM CCS): I.3.6 [Computer Graphics]: Methodology and Techniques
Image Based Interactive Rendering with View Dependent Geometry
(Blackwell Publishers, Inc and the Eurographics Association, 2003) Evers-Senne, J.-F.; Koch, R.
In this paper we present a novel approach for interactive rendering of virtual views from real image sequences.Combining the concepts of light fields, depth-compensated image warping and view dependent texture mapping,this plenoptic modeling approach can handle large and complex scenes. A portable, handheld multi-camera systemhas been developed that allows to record multiple image streams by simply walking around the scene. Theseimage streams are automatically calibrated and depth maps for all views are generated as input to the renderingstage. For rendering a view dependent warping surface is constructed on the fly and depth-compensated imageinterpolation is applied with view-dependent texture mapping. Rendering quality is scalable to allow fast previewand to achieve high-end quality with the same approach. The system can handle large and geometrically complexscenes with hundreds of real images at interactive rates.Categories and Subject Descriptors (according to ACM CCS): I.3.3 [Computer Graphics]: Viewing algorithms, I.4.1[Image Processing and Computer Vision]: Digitization and Image Capture, I.4.8 [Image Processing and ComputerVision]: Scene Analysis
A Few Good Lines: Suggestive Drawing of 3D Models
(Blackwell Publishers, Inc and the Eurographics Association, 2003) Sousa, Mario Costa; Prusinkiewicz, Przemyslaw
We present a method for rendering 3D models in the traditionalline-drawing style used in artistic and scientificillustrations. The goal is to suggest the 3D shape of the objectsusing a small number of lines drawn with carefullychosen line qualities. The system combines several known techniquesinto a simple yet effective non-photorealisticline renderer. Feature edges related to the outline and interiorof a given 3D mesh are extracted, segmented, andsmoothed, yielding chains of lines with varying path, length, thickness,gaps, and enclosures. The paper includessample renderings obtained for a variety of models.
BDAM - Batched Dynamic Adaptive Meshes for High Performance Terrain Visualization
(Blackwell Publishers, Inc and the Eurographics Association, 2003) Cignoni, P.; Ganovelli, F.; Gobbetti, E.; Marton, F.; Ponchio, F.; Scopigno, R.
This paper describes an efficient technique for out-of-core rendering and management of large textured terrainsurfaces. The technique, called Batched Dynamic Adaptive Meshes (BDAM), is based on a paired tree structure:a tiled quadtree for texture data and a pair of bintrees of small triangular patches for the geometry. These smallpatches are TINs and are constructed and optimized off-line with high quality simplification and tristrippingalgorithms. Hierarchical view frustum culling and view-dependent texture and geometry refinement is performedat each frame through a stateless traversal algorithm. Thanks to the batched CPU/GPU communication model,the proposed technique is not processor intensive and fully harnesses the power of current graphics hardware.Both preprocessing and rendering exploit out-of-core techniques to be fully scalable and to manage large terraindatasets.Categories and Subject Descriptors (according to ACM CCS): I.3.3 [Computer Graphics]: Picture and Image Generation;I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism.
Open Issues in Photo-realistic Rendering
(Blackwell Publishers, Inc and the Eurographics Association, 2003) Purgathofer, Werner
For more than two decades Computer graphics researchers have tried to achieve photo-realism in their images as reliable as possible, mainly by simulating the physical laws of light and adding one effect after the other. The recent years have brought a change of efforts towards real-time methods, easy-to-use systems, integration with vision, modelling tools and the like. The quality of images is mostly accepted as sufficient for real world applications, but where are we really? There are still numerous problems to be solved, and there is notable progress in these areas. No question, the plug-in philosophy of some commercial products has enabled several of these new techniques to be distributed quite fast. But unfortunately, many other of these developments happen in isolated systems for the pure purpose of publication, and never make it into commercial software. This presentation wants to make people more aware of such activities, and evaluate the steps we still have to go towards perfect photo-realism.The talk will start with an attempt to give a brief overview of the rendering history, highlighting the main research directions at different times. It will explain the driving forces of the developments, which are complexity, speed, and accuracy, and maybe also expression in recent years. Solved and unsolved areas are examined, and compared to practically solved but theoretically incomplete topics such as translucency, tone mapping, light source and BTF descriptions, and error metrics for image quality evaluation. The difference lies mainly in the difference between believable, correct, and predictive images. Also, for really realistic images modelling complexity is still an issue. Finally, some recent work on polarization and fluorescence is presented.
Animating Hair with Loosely Connected Particles
(Blackwell Publishers, Inc and the Eurographics Association, 2003) Bando, Yosuke; Chen, Bing-Yu; Nishita, Tomoyuki
This paper presents a practical approach to the animation of hair at an interactive frame rate. In our approach,we model the hair as a set of particles that serve as sampling points for the volume of the hair, which covers thewhole region where hair is present. The dynamics of the hair, including hair-hair interactions, is simulated usingthe interacting particles. The novelty of this approach is that, as opposed to the traditional way of modeling hair,we release the particles from tight structures that are usually used to represent hair strands or clusters. Therefore,by making the connections between the particles loose while maintaining their overall stiffness, the hair can bedynamically split and merged during lateral motion without losing its lengthwise coherence.Categories and Subject Descriptions (according to ACM CCS): I.3.7 [Computer Graphics]: Three-DimensionalGraphics and Realism, I.3.3 [Computer Graphics]: Picture/Image Generation
Compression of 2D Vector Fields Under Guaranteed Topology Preservation
(Blackwell Publishers, Inc and the Eurographics Association, 2003) Theisel, H.; Rossl, Ch.; Seidel, H.-P.
In this paper we introduce a new compression technique for 2D vector fields which preserves the complete topology, i.e., the critical points and the connectivity of the separatrices. As the theoretical foundation of the algorithm, we show in a theorem that for local modifications of a vector field, it is possible to decide entirely by a local analysis whether or not the global topology is preserved. This result is applied in a compression algorithm which is based on a repeated local modification of the vector field - namely a repeated edge collapse of the underlying piecewise linear domain. We apply the compression technique to a number of data sets with a complex topology and obtain significantly improved compression ratios in comparison to pre-existing topology-preserving techniques.
On Visual Similarity Based 3D Model Retrieval
(Blackwell Publishers, Inc and the Eurographics Association, 2003) Chen, Ding-Yun; Tian, Xiao-Pei; Shen, Yu-Te; Ouhyoung, Ming
Sub-Voxel Topology Control for Level-Set Surfaces
(Blackwell Publishers, Inc and the Eurographics Association, 2003) Bischoff, Stephan; Kobbelt, Leif
Active contour models are an efficient, accurate, and robust tool for the segmentation of 2D and 3D image data.In particular, geometric deformable models (GDM) that represent an active contour as the level set of an implicitfunction have proven to be very effective. GDMs, however, do not provide any topology control, i.e. contours maymerge or split arbitrarily and hence change the genus of the reconstructed surface. This behavior is inadequate insettings like the segmentation of organic tissue or other objects whose genus is known beforehand. In this paperwe describe a novel method to overcome this limitation while still preserving the favorable properties of the GDMsetup. We achieve this by adding (sparse) topological information to the volume representation at locations whereit is necessary to locally resolve topological ambiguities. Since the sparse topology information is attached to theedges of the voxel grid, we can reconstruct the interfaces where the deformable surface touches itself at sub-voxelaccuracy. We also demonstrate the efficiency and robustness of our method.
Shadow Volumes on Programmable Graphics Hardware
(Blackwell Publishers, Inc and the Eurographics Association, 2003) Brabec, Stefan; Seidel, Hans-Peter
One of the best choices for fast, high quality shadows is the shadow volume algorithm. However, for real timeapplications the extraction of silhouette edges can significantly burden the CPU, especially with highly tessellatedinput geometry or when complex geometry shaders are applied.In this paper we show how this last, expensive part of the shadow volume method can be implemented on programmablegraphics hardware. This way, the originally hybrid shadow volumes algorithm can now be reformulatedas a purely hardware-accelerated approach.The benefits of this implementation is not only the increase in speed. Firstly, all computations now run on thesame hardware resulting in consistent precision within all steps of the algorithm. Secondly, programmable vertextransformations are no longer problematic when applied to shadow casting objects.Categories and Subject Descriptors (according to ACM CCS): I.3.1 [Computer Graphics]: Hardware Architecture;I.3.3 [Computer Graphics]: Picture/Image Generation; I.3.7 [Computer Graphics]: Three-Dimensional Graphicsand Realism
Adaptive Logarithmic Mapping For Displaying High Contrast Scenes
(Blackwell Publishers, Inc and the Eurographics Association, 2003) Drago, F.; Myszkowski, K.; Annen, T.; Chiba, N.
We propose a fast, high quality tone mapping technique to display high contrast images on devices with limited dynamicrange of luminance values. The method is based on logarithmic compression of luminance values, imitatingthe human response to light. A bias power function is introduced to adaptively vary logarithmic bases, resultingin good preservation of details and contrast. To improve contrast in dark areas, changes to the gamma correctionprocedure are proposed. Our adaptive logarithmic mapping technique is capable of producing perceptually tunedimages with high dynamic content and works at interactive speed. We demonstrate a successful application of ourtone mapping technique with a high dynamic range video player enabling to adjust optimal viewing conditions forany kind of display while taking into account user preference concerning brightness, contrast compression, anddetail reproduction.Categories and Subject Descriptors (according to ACM CCS): I.3.3 [Image Processing and Computer Vision]: Image Representation
Multiresolution Surface Representation Based on Displacement Volumes
(Blackwell Publishers, Inc and the Eurographics Association, 2003) Botsch, Mario; Kobbelt, Leif
We propose a new representation for multiresolution models which uses volume elements enclosed between thedifferent resolution levels to encode the detail information. Keeping these displacement volumes locally constantduring a deformation of the base surface leads to a natural behaviour of the detail features. The correspondingreconstruction operator can be implemented efficiently by a hierarchical iterative relaxation scheme, providingclose to interactive response times for moderately complex models.Based on this representation we implement a multiresolution editing tool for irregular polygon meshes that allowsthe designer to freely edit the base surface of a multiresolution model without having to care about self-intersectionsin the respective detailed surface. We demonstrate the effectiveness and robustness of the reconstructionby several examples with real-world data.
Field Functions for Blending Range Controls on Soft Objects
(Blackwell Publishers, Inc and the Eurographics Association, 2003) Hsu, P. C.; Lee, C.
This paper proposes new field functions that have adjustable inner radius and outer radius of influence. Incorporatingthe proposed field functions with soft object modeling, soft blending, Ricci's super-ellipsoid blends, Perlin'sset operations, and R-functions, etc. can have blending range controls by adjusting the inner and the outer radiiof influence of given field functions. As a result, the sizes of the resulting blending surfaces on soft objects willnot be restricted by the sizes of the blended primitive soft objects and can be enlarged and shrunk freely withoutdeforming the overall shapes of blended primitive soft objects. In addition, a small soft object can have a largeblending region, and a large one can have a small blending regionCategories and Subject Descriptors (according to ACM CCS): I.3.5 [Computer Graphics]: Computational Geometry and Object Modeling - Curve, surface, solid and object representations
Volumetric cell-and-portal generation
(Blackwell Publishers, Inc and the Eurographics Association, 2003) Haumont, D.; Debeir, O.; Sillion, F.
We present an algorithm to generate a cell-and-portal decomposition of general indoor scenes. The method is an adaptation of the 3D watershed transform, computed on a distance-to-geometry sampled field. The watershed is processed using a flooding analogy in the distance field space. Flooding originates from local minima, each minimum producing a region. Portals are built as needed to avoid the merging of regions during their growth. As a result, the cell-and-portal decomposition is closely linked to the structure of the models. In a building, the algorithm finds all the rooms, doors and windows. To restrict the memory load, a hierarchical implementation of the algorithm is presented. We also explain how to handle possible model degeneracies -such as cracks, holes and interpenetrating geometries- using a pre-voxelisation step. The hierarchical algorithm, preceded when necessary by the pre-voxelisation, was tested on a large range of models. We show that it is able to deal with classical architectural models, as well as cave-like environments and large mixed indoor/outdoor scenes. Thanks to the intermediate distance field representation, the algorithm can be used regardless of the way the model is represented: it deals with parametric curves, implicit surfaces, volumetric data and polygon soups in a unified way.
Progressive Simplification of Tetrahedral Meshes Preserving All Isosurface Topologies
(Blackwell Publishers, Inc and the Eurographics Association, 2003) Chiang, Yi-Jen; Lu, Xiang
In this paper, we propose a novel technique for constructing multiple levels of a tetrahedral volume dataset whilepreserving the topologies of all isosurfaces embedded in the data. Our simplification technique has two majorphases. In the segmentation phase, we segment the volume data into topological-equivalence regions, that is, thesub-volumes within each of which all isosurfaces have the same topology. In the simplification phase, we simplifyeach topological-equivalence region independently, one by one, by collapsing edges from the smallest to the largesterrors (within the user-specified error tolerance, for a given error metrics), and ensure that we do not collapseedges that may cause an isosurface-topology change. We also avoid creating a tetrahedral cell of negative volume(i.e., avoid the fold-over problem). In this way, we guarantee to preserve all isosurface topologies in the entiresimplification process, with a controlled geometric error bound. Our method also involves several additionalnovel ideas, including using the Morse theory and the implicit fully augmented contour tree, identifying typesof edges that are not allowed to be collapsed, and developing efficient techniques to avoid many unnecessary orexpensive checkings, all in an integrated manner. The experiments show that all the resulting isosurfaces preservethe topologies, and have good accuracies in their geometric shapes. Moreover, we obtain nice data-reductionrates, with competitively fast running times.
ShieldTester: Cell-to-Cell Visibility Test for Surface Occluders
(Blackwell Publishers, Inc and the Eurographics Association, 2003) Navazo, I.; Rossignac, J.; Jou, J.; Shariff, R.
We present a novel Cell-To-Cell Visibility (C2CV) algorithm, which given two polyhedra, AandBand a connectedand oriented manifold triangle mesh, S offers a simple, fast and conservative test for detecting when A and B areoccluded from each other by S. Previously disclosed C2CV algorithms either relied on costly occlusion fusion orwere restricted to convex or "apparently convex" occluders, which makes them inappropriate for scenes wherepotential occluders are arbitrary triangulated surfaces, such as the body of a car or a portion of a terrain. Thesimplicity of our C2CV algorithm, named ShieldTester, stems from a new Occlusion Theorem, introduced herewhich permits to establish occlusion by computing the intersection of S with a single ray from a vertex ofAtoa vertex ofB. ShieldTester may be used to establish that pairs of cells in a subdivision of space are hidden fromeach other by a relatively large surface occluder, so that when the viewer is in one cell, the objects in the othercell need not be displayed.Categories and Subject Descriptors (according to ACM CCS): I.3.3 [Computer Graphics]: Computational Geometryand Object Modeling: Occlussion Culling, Visibility Test, Triangle Meshes
Freeform Shape Representations for Efficient Geometry Processing
(Blackwell Publishers, Inc and the Eurographics Association, 2003) Kobbelt, Leif
The most important concepts for the handling and storage of freeform shapes in geometry processing applications are parametric representations and volumetric representations. Both have their specific advantages and drawbacks. While the algebraic complexity of volumetric representations is independent from the shape complexity, the domain of a parametric representation usually has to have the same structure as the surface itself (which sometimes makes it necessary to update the domain when the surface is modified).On the other hand, the topology of a parametrically defined surface can be controlled explicitly while in a volumetric representation, the surface topology can change accidentally during deformation. A volumetric representation reduces distance queries or inside/outside tests to mere function evaluations but the geodesic neighborhood relation between surface points is difficult to resolve. As a consequence, it seems promising to combine parametric and volumetric representations to effectively exploit both advantages.In this talk, a number of projects are presented and discussed in which such a combination leads to efficient and numerically stable algorithms for the solution of various geometry processing tasks. Applications include global error control for mesh decimation and smoothing, topology control for level-set surfaces, and shape modeling with unstructured point clouds.

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