Browsing by Author "Ozturk, Aydn"

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    Real-time kd-tree based importance sampling of environment maps
    (2012) Serkan Ergun; Murat Kurt; Aydin Öztürk; Ergun, Serkan; Kurt, Murat; Ozturk, Aydn
    We present a new real-time importance sampling algorithm for environment maps. Our method is based on representing environment maps using kd-tree structures and generating samples with a single data lookup. An efficient algorithm has been developed for realtime image-based lighting applications. In this paper we compared our algorithm with Inversion method [Fishman 1996]. We show that our proposed algorithm provides compactness and speedup as compared to Inversion method. Based on a number of rendered images we have demonstrated that in a fixed time frame the proposed algorithm produces images with a lower noise than that of the Inversion method. We also demonstrate that our algorithm can successfully represent a wide range of material types. © 2013 ACM. © 2013 Elsevier B.V. All rights reserved.
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    Representing BRDF by wavelet transformation of pair-copula constructions
    (2012) Ahmet Bilgili; Aydin Öztürk; Murat Kurt; Kurt, Murat; Bilgili, Ahmet; Ozturk, Aydn
    Bidirectional Reflectance Distribution Functions (BRDFs) are wellknown functions in computer graphics and these special functions represent the surface reflectance of materials. BRDFs can be viewed as multivariate probability density function (pdf) of incoming photons leaving in a particular outgoing direction. However constructing a multivariate probability distribution for modeling a given BRDF is difficult. A family of distributions namely Copula distributions have been used to approximate BRDF. In this work we employ the Pair-Copula constructions to represent the measured BRDF densities. As the measured BRDF densities have large storage needs we use Wavelet transforms for a compact BRDF representation. We also compare the proposed BRDF representation with a number of well-known BRDF models and show that our compact BRDF representation provides good approximation to measured BRDF data. © 2013 ACM. © 2013 Elsevier B.V. All rights reserved.