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    Efficient Representation of Layered Depth Images for Real-time Volumetric Tests
    (The Eurographics Association, 2008) Trapp, Matthias; Döllner, Jürgen; Ik Soo Lim and Wen Tang
    Representing Layered Depth Images (LDI) as 3D texture can be used to approximate complex, arbitrarily shaped volumes on graphics hardware. Based on this concept, a number of real-time applications such as collision detection or 3D clipping against multiple volumes can be implemented efficiently using programmable hardware. One major drawback of this image-based representation is the high video memory consumption. To compensate that disadvantage, this paper presents a concept and associated algorithms that enable a lossless, efficient LDI representation which is especially designed for the usage within shader programs. The concept comprises the application of a viewpoint selection, a cropping, and a compression algorithm. We evaluated our algorithm with different test cases and show possible use cases.
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    Image Abstraction by Structure Adaptive Filtering
    (The Eurographics Association, 2008) Kyprianidis, Jan Eric; Döllner, Jürgen; Ik Soo Lim and Wen Tang
    In this work we present a framework of automatic non-photorealistic image processing techniques that create simplified stylistic illustrations from color images, videos and 3D renderings. To smooth low-contrast regions while preserving edges, we present a new fast separated implementation of the bilateral filter. Our approach works by filtering in direction of the gradient and then filtering the intermediate result in perpendicular direction. When applied iteratively, our approach does not suffer from horizontal or vertical artifacts and creates smooth output at curved boundaries. To extract salient important edges we first apply a one-dimensional difference-of-Gaussians filter in direction of the gradient and then apply smoothing along a flow field which we derive from the smoothed structure tensor. Our method creates smooth coherent output for line and curve segments.