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Subject: shading × Start date: 2000 × End date: 2009 × Has files: true ×

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Now showing 1 - 10 of 13
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    An Eigenvector Method for Surface Recovery
    (The Eurographics Association, 2003) Robles-Kelly, A.; Hancock, E.R.; Peter Hall and Philip Willis
    In this paper we explore how spectral methods for graph seriation can be used to develop a new shape-fromshading algorithm. We characterise the field of surface normals using a transition matrix whose elements are computed from the sectional curvature between different image locations. We use a graph seriation method to define a curvature minimising surface integration path for the purposes of height reconstruction. To smooth the reconstructed surface, we fit quadric patches to the height data. The smoothed surface normal directions are updated ensuring compliance with Lambert's law. The processes of height recovery and surface normal adjustment are interleaved and iterated until a stable surface is obtained. We provide results on synthetic and real-world imagery.
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    Preserving Realism in Real-Time Rendering of Bidirectional Texture Functions
    (The Eurographics Association, 2003) Meseth, Jan; Müller, Gero; Klein, Reinhard; Dirk Reiners
    The Bidirectional Texture Function (BTF) is a suitable representation for the appearance of highly detailed surface structures under varying illumination and viewing conditions. Since real-time rendering of the full BTF data is currently not feasible, approximations of the six-dimensional BTF are used such that the amount of data is reduced and current graphics hardware can be exploited. While existing methods work well for materials with low depth variation, realism is lost if the depth variation grows. In this paper we analyze this problem and devise a new real-time rendering method, which provides signi cant improvements with respect to realism for such highly structured materials without sacri cing the general applicability and speed of previous algorithms. We combine our approach with texture synthesis methods to drastically reduce the texture memory requirements and demonstrate the capabilities of our new rendering method with several examples.
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    Incremental and Hierarchical Hilbert Order Edge Equation Polygon Rasterization
    (The Eurographics Association, 2001) McCool, Michael D.; Wales, Cluis; Moule, Kevin; Kurt Akeley and Ulrich Neumann
    A rasterization algorithm must efficiently generate pixel fragments from geometric descriptions of primitives. ln order to accomplish per-pixel shading, shading parameters must also be interpolated across the primitive in a perspective-correct manner. lf some of these parameters are to be interpreted in later stages of the pipeline directly or indirectly as texture coordinates, then translating spatial and parametric coherence into temporal coherence will improve texture cache performance. Finally, if framebuffer access is also organized around cached blocks, then organizing rasterization so fragments are generated in block-sequential order will maximize framebuffer cache performance. Hilbert-order rasterization accomplishes these goals, and also permits efficient incrementale valuation of edge and interpolation equations.
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    Vertex-based Anisotropic Texturing
    (The Eurographics Association, 2001) Olano, Marc; Mukherjee, Shrijeet; Dorbie, Angus; Kurt Akeley and Ulrich Neumann
    MIP mapping is a common method used by graphics hardware to avoid texture aliasing. In many situations, MIP mapping over-blurs in one direction to prevent aliasing in another. Anisotropic texturing reduces this blurring by allowing differing degrees of filtering in different directions, but is not as common in hardware due to the implementation complexity of current techniques. We present a new algorithm that enables anisotropic texturing on any current MIP map graphics hardware supporting MIP level biasing, available in OpenGL 7.2 or through the GLEXT-texture-lod-bias or GL-SGIX-texture-lod-bias OpenGL extensions. The new algorithm computes anisotropic filter footprint parameters per vertex. It constructs the anisotropic filter out of several MIP map texturing passes or multitexture lookups. Each lookup uses MIP level bias and perturbed texture coordinates to place one probe used to construct the more complex filter profile.
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    Realistic Real-Time Hair Simulation and Rendering
    (The Eurographics Association, 2005) Jung, Yvonne; Rettig, Alexander; Klar, Oliver; Lehr, Timo; Mike Chantler
    We present a method for realistic rendering and simulation of human hair in real-time, which is suitable for the use in complex virtual reality applications. Neighbouring hairs are combined into wisps and animated with our cantilever beam based simulation system, which runs numerically stable and with interactive update rates. The rendering algorithm utilizes latest graphics hardware features and can even handle light coloured hair by including anisotropic reflection and internal transmission.
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    A Quadrilateral Rendering Primitive
    (The Eurographics Association, 2004) Hormann, Kai; Tarini, Marco; Tomas Akenine-Moeller and Michael McCool
    The only surface primitives that are supported by common graphics hardware are triangles and more complex shapes have to be triangulated before being sent to the rasterizer. Even quadrilaterals, which are frequently used in many applications, are rendered as a pair of triangles after splitting them along either diagonal. This creates an undesirable C1-discontinuity that is visible in the shading or texture signal. We propose a new method that overcomes this drawback and is designed to be implemented in hardware as a new rasterizer. It processes a potentially non-planar quadrilateral directly without any splitting and interpolates attributes smoothly inside the quadrilateral. This interpolation is based on a recent generalization of barycentric coordinates that we adapted to handle perspective correction and situations in which a quadrilateral is partially behind the point of view.
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    GPU-based Real-time On-surface Droplet Flow in X3D
    (The Eurographics Association, 2009) Jung, Yvonne; Behr, Johannes; Dieter W. Fellner and Alexei Sourin and Johannes Behr and Krzysztof Walczak
    This paper presents a method for the GPU-based real-time simulation of droplet flows on 3D surfaces. It is also outlined, how this approach can be embedded into X3D. Therefore, a concept and its implementation is presented, which is able to simulate droplet flow on almost any surface of a given 3D model. The droplet flow is advanced in time according to the applied external forces, and leaves a trail of liquid behind. Different viscosities are considered as well as the contact angles of droplets that are placed on the surface. Because simulation and rendering of droplet flow is completely handled on the GPU, all fluid information is hold entirely in texture memory. Hence, real-time framerates are achieved and moreover, the number of simulated drops does not influence performance.
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    Algorithms for Division Free Perspective Correct Rendering
    (The Eurographics Association, 2000) Barenbrug, B.; Peters, F.J.; Overveld, C.W.A.M. van; I. Buck and G. Humphreys and P. Hanrahan
    Well known implementations for perspective correct rendering of planar polygons require a division per rendered pixel. Such a division is better to be avoided as it is an expensive operation in terms of silicon gates and clock cycles. In this paper we present a family of efficient midpoint algorithms that can be used to avoid division operators. These algorithms do not require more than a small number of additions per pixel. We show how these can be embedded in scan line algorithms and in algorithms that use mipmaps. Experiments with software implementations show that the division free algorithms are a factor of two faster, provided that the polygons are not too small. These algorithms are however most profitable when realised in hardware.
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    Perlin Noise Pixel Shaders
    (The Eurographics Association, 2001) Hart, John C.; Kurt Akeley and Ulrich Neumann
    While working on a method for supporting real-time procedural solid texturing, we developed a general purpose multipass pixel shader to generate the Perlin noise function. We implemented this algorithm on SGI workstations using accelerated OpenGL PixelMap and PixelTransfer operations, achieving a rate of 2.5 Hz for a 256x256 image. We also implemented the noise algorithm on the NVidia GeForce2 using register combiners. Our register combiner implementation required 375 passes, but ran at 1.3 Hz. This exercise illustrated a variety of abilities and shortcomings of current graphics hardware. The paper concludes with an exploration of directions for expanding pixel shading hardware to further support iterative multipass pixel-shader applications.
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    The F-Buffer: A Rasterization-Order FIFO Buffer for Multi-Pass Rendering
    (The Eurographics Association, 2001) Mark, William R.; Proudfoot, Kekoa; Kurt Akeley and Ulrich Neumann
    Multi-pass rendering is a common method of virtualizing graphics hardware to overcome limited resources. Most current multi-pass rendering techniques use the RGBA framebuffer to store intermediate results between each pass. This method of storing intermediate results makes it difficult to conectly render partially-transparent surfaces, and reduces the performance of shaders that need to preserve more than one intermediate result between passes. We propose an alternative approach to storing intermediate results that solves these problems. This approach stores intermediate colors (or other values) that are generated by a rendering pass in a FIFO buffer as the values exit the fragment pipeline. On a subsequent pass, the contents of the FIFO buffer are fed into the top of the fragment pipeline. We refer to this FIFO buffer as a fragment-stream buffer (or F-buffer), because this approach has the effect of associating intermediate results with particular rasterization fragments, rather than with an (x,y) location in the framebuffer. Implementing an F-buffer requires some changes to current mainstream graphics architectures, but these changes can be minor. We describe the designs pace associated with implementing an F-buffer, and compare the F-buffer to recirculating pipeline designs. We implement F-buffers in the Mesa software renderer, and demonstrate our programmable-shading system running on top of this renderer.