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Item Efficient Rendering of Local Subsurface Scattering(The Eurographics Association and Blackwell Publishing Ltd., 2005) Mertens, Tom; Kautz, Jan; Bekaert, Philippe; Van Reeth, Frank; Seidel, Hans-PeterA novel approach is presented to efficiently render local subsurface scattering effects. We introduce an importance sampling scheme for a practical subsurface scattering model. It leads to a simple and efficient rendering algorithm, which operates in image space, and which is even amenable for implementation on graphics hardware. We demonstrate the applicability of our technique to the problem of skin rendering, for which the subsurface transport of light typically remains local. Our implementation shows that plausible images can be rendered interactively using hardware acceleration.Item Deblurring by Matching(The Eurographics Association and Blackwell Publishing Ltd, 2009) Ancuti, Cosmin; Ancuti, Codruta Orniana; Bekaert, PhilippeRestoration of the photographs damaged by the camera shake is a challenging task that manifested increasing attention in the recent period. Despite of the important progress of the blind deconvolution techniques, due to the ill-posed nature of the problem, the finest details of the kernel blur cannot be recovered entirely. Moreover, the additional constraints and prior assumptions make these approaches to be relative limited.In this paper we introduce a novel technique that removes the undesired blur artifacts from photographs taken by hand-held digital cameras. Our approach is based on the observation that in general several consecutive photographs taken by the users share image regions that project the same scene content. Therefore, we took advantage of additional sharp photographs of the same scene. Based on several invariant local feature points, filtered from the given blurred/non-blurred images, our approach matches the keypoints and estimates the blur kernel using additional statistical constraints.We also present a simple deconvolution technique that preserves edges while minimizing the ringing artifacts in the restored latent image. The experimental results prove that our technique is able to infer accurately the blur kernel while reducing significantly the artifacts of the spoilt images.Item Convolution Shadow Maps(The Eurographics Association, 2007) Annen, Thomas; Mertens, Tom; Bekaert, Philippe; Seidel, Hans-Peter; Kautz, Jan; Jan Kautz and Sumanta PattanaikWe present Convolution Shadow Maps, a novel shadow representation that affords efficient arbitrary linear filtering of shadows. Traditional shadow mapping is inherently non-linear w.r.t. the stored depth values, due to the binary shadow test. We linearize the problem by approximating shadow test as a weighted summation of basis terms. We demonstrate the usefulness of this representation, and show that hardware-accelerated anti-aliasing techniques, such as tri-linear filtering, can be applied naturally to Convolution Shadow Maps. Our approach can be implemented very efficiently in current generation graphics hardware, and offers real-time frame rates.Item Texture Transfer Using Geometry Correlation(The Eurographics Association, 2006) Mertens, Tom; Kautz, Jan; Chen, Jiawen; Bekaert, Philippe; Durand, Frédo; Tomas Akenine-Moeller and Wolfgang HeidrichTexture variation on real-world objects often correlates with underlying geometric characteristics and creates a visually rich appearance. We present a technique to transfer such geometry-dependent texture variation from an example textured model to new geometry in a visually consistent way. It captures the correlation between a set of geometric features, such as curvature, and the observed diffuse texture. We perform dimensionality reduction on the overcomplete feature set which yields a compact guidance field that is used to drive a spatially varying texture synthesis model. In addition, we introduce a method to enrich the guidance field when the target geometry strongly differs from the example. Our method transfers elaborate texture variation that follows geometric features, which gives 3D models a compelling photorealistic appearance.