31-Issue 4

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https://diglib.eg.org/handle/10.2312/173

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Browsing 31-Issue 4 by Subject "I.3.3 [Computer Graphics]"

Now showing 1 - 4 of 4
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    Analytic Tangent Irradiance Environment Maps for Anisotropic Surfaces
    (The Eurographics Association and Blackwell Publishing Ltd., 2012) Mehta, Soham Uday; Ramamoorthi, Ravi; Meyer, Mark; Hery, Christophe; Fredo Durand and Diego Gutierrez
    Environment-mapped rendering of Lambertian isotropic surfaces is common, and a popular technique is to use a quadratic spherical harmonic expansion. This compact irradiance map representation is widely adopted in interactive applications like video games. However, many materials are anisotropic, and shading is determined by the local tangent direction, rather than the surface normal. Even for visualization and illustration, it is increasingly common to define a tangent vector field, and use anisotropic shading. In this paper, we extend spherical harmonic irradiance maps to anisotropic surfaces, replacing Lambertian reflectance with the diffuse term of the popular Kajiya-Kay model. We show that there is a direct analogy, with the surface normal replaced by the tangent. Our main contribution is an analytic formula for the diffuse Kajiya-Kay BRDF in terms of spherical harmonics; this derivation is more complicated than for the standard diffuse lobe. We show that the terms decay even more rapidly than for Lambertian reflectance, going as l??3, where l is the spherical harmonic order, and with only 6 terms (l
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    Intrinsic Images by Clustering
    (The Eurographics Association and Blackwell Publishing Ltd., 2012) Garces, Elena; Munoz, Adolfo; Lopez-Moreno, Jorge; Gutierrez, Diego; Fredo Durand and Diego Gutierrez
    Decomposing an input image into its intrinsic shading and reflectance components is a long-standing ill-posed problem. We present a novel algorithm that requires no user strokes and works on a single image. Based on simple assumptions about its reflectance and luminance, we first find clusters of similar reflectance in the image, and build a linear system describing the connections and relations between them. Our assumptions are less restrictive than widely-adopted Retinex-based approaches, and can be further relaxed in conflicting situations. The resulting system is robust even in the presence of areas where our assumptions do not hold. We show a wide variety of results, including natural images, objects from the MIT dataset and texture images, along with several applications, proving the versatility of our method.
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    Per-Vertex Defocus Blur for Stochastic Rasterization
    (The Eurographics Association and Blackwell Publishing Ltd., 2012) Munkberg, Jacob; Toth, Robert; Akenine-Möller, Tomas; Fredo Durand and Diego Gutierrez
    We present user-controllable and plausible defocus blur for a stochastic rasterizer. We modify circle of confusion coefficients per vertex to express more general defocus blur, and show how the method can be applied to limit the foreground blur, extend the in-focus range, simulate tilt-shift photography, and specify per-object defocus blur. Furthermore, with two simplifying assumptions, we show that existing triangle coverage tests and tile culling tests can be used with very modest modifications. Our solution is temporally stable and handles simultaneous motion blur and depth of field.
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    A Stylized Approach for Pencil Drawing from Photographs
    (The Eurographics Association and Blackwell Publishing Ltd., 2012) Yang, Heekyung; Kwon, Yunmi; Min, Kyungha; Fredo Durand and Diego Gutierrez
    We present a stylized scheme that produces pencil drawings in a range of styles from an image. To produce controllable pencil drawing effects and remedy the problems of existing convolution-based schemes, we develop a swing bilateral LIC (SBL) filter. Our first approach to express the styled pencil drawings is to control the directions of pencil strokes that depicts both shapes and smooth tone. Another approach is to produce colors of pencil drawings by sampling colors from real color pencils. The third approach is to mimic the artistic technique that increases the details of drawings in a progressive manner. We present drawings in several styles and compare some of them directly with illustrations taken from an artists' work.