32-Issue 2

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https://diglib.eg.org/handle/10.2312/180

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Browsing 32-Issue 2 by Subject "Computer Graphics"

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    Removing the Noise in Monte Carlo Rendering with General Image Denoising Algorithms
    (The Eurographics Association and Blackwell Publishing Ltd., 2013) Kalantari, Nima Khademi; Sen, Pradeep; I. Navazo, P. Poulin
    Monte Carlo rendering systems can produce important visual effects such as depth of field, motion blur, and area lighting, but the rendered images suffer from objectionable noise at low sampling rates. Although years of research in image processing has produced powerful denoising algorithms, most of them assume that the noise is spatially-invariant over the entire image and cannot be directly applied to denoise Monte Carlo rendering. In this paper, we propose a new approach that enables the use of any spatially-invariant image denoising technique to remove the noise in Monte Carlo renderings. Our key insight is to use a noise estimation metric to locally identify the amount of noise in different parts of the image, coupled with a multilevel algorithm that denoises the image in a spatially-varying manner using a standard denoising technique. We also propose a new way to perform adaptive sampling that uses the noise estimation metric to identify the noisy regions in which to place more samples. We show that our framework runs in a few seconds with modern denoising algorithms and produces results that outperform state-of-the-art techniques in Monte Carlo rendering.
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    Sifted Disks
    (The Eurographics Association and Blackwell Publishing Ltd., 2013) Ebeida, Mohamed S.; Mahmoud, Ahmed H.; Awad, Muhammad A.; Mohammed, Mohammed A.; Mitchell, Scott A.; Rand, Alexander; Owens, John D.; I. Navazo, P. Poulin
    We introduce the Sifted Disk technique for locally resampling a point cloud in order to reduce the number of points. Two neighboring points are removed and we attempt to find a single random point that is sufficient to replace them both. The resampling respects the original sizing function; In that sense it is not a coarsening. The angle and edge length guarantees of a Delaunay triangulation of the points are preserved. The sifted point cloud is still suitable for texture synthesis because the Fourier spectrum is largely unchanged. We provide an efficient algorithm, and demonstrate that sifting uniform Maximal Poisson-disk Sampling (MPS) and Delaunay Refinement (DR) points reduces the number of points by about 25 percent, and achieves a density about 1/3 more than the theoretical minimum. We show two-dimensional stippling and meshing applications to demonstrate the significance of the concept.