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Ray Tracing NPR-Style Feature Lines. A.N.M. Imroz Choudhury, S.G. Parker. In Proceedings of the 7th International Symposium on Non-Photorealistic Animation and Rendering (NPAR) 2009, pp. 5--14. 2009.
We present an algorithm for rendering high-quality line primitives of controllable on-screen width within a ray tracing framework, which can render simple NPR-style feature lines, including silhouette edges, crease lines, and primitive intersection lines. The algorithm is based on a variant of cone tracing, which measures distances in screen space and is used to detect and render feature lines. This technique opens ray tracing up to previously difficult or impossible styles of rendering, such as mesh visualization, as well as a variety of NPR techniques, such as apparent ridges.
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An Analytical Solution to Single Scattering in Homogeneous Participating Media. V. Pegoraro, S.G. Parker. In Computer Graphics Forum (Proceedings of the 30th Eurographics Conference), Vol. 28, No. 2, pp. 329--335. 2009.
Despite their numerous applications, efficiently rendering participating media remains a challenging task due to the intricacy of the radiative transport equation. As they provide a generic means of solving a wide variety of problems, numerical methods are most often used to solve the air-light integral even under simplifying assumptions. In this paper, we present a novel analytical approach to single scattering from isotropic point light sources in homogeneous media. We derive the first closed-form solution to the air-light integral in isotropic media and extend this formulation to anisotropic phase functions. The technique relies neither on pre-computation nor on storage, and we provide a practical implementation allowing for an explicit control on the accuracy of the solutions. Finally, we demonstrate its quantitative and qualitative benefits over both previous numerical and analytical approaches.
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An Analytical Approach to Single Scattering for Anisotropic Media and Light Distributions. V. Pegoraro, M. Schott, S.G. Parker. In Proceedings of the 35th Graphics Interface Conference. 2009.
Despite their numerous applications, efficiently rendering participating media remains a challenging task due to the intricacy of the radiative transport equation. While numerical techniques remain the method of choice for addressing complex problems, a closed form solution to the air-light integral in optically thin isotropic media was recently derived. In this paper, we extend this work and present a novel analytical approach to single scattering from point light sources in homogeneous media. We propose a combined formulation of the air-light integral which allows both anisotropic phase functions and light distributions to be adequately handled. The technique relies neither on precomputation nor on storage, and we provide a robust and efficient implementation allowing for an explicit control on the accuracy of the results. Finally, the performance characteristics of the method on graphics hardware are evaluated and demonstrate its suitability to real-time applications.
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Reduced Dual-Formulation for Analytical Anisotropic Single Scattering. V. Pegoraro, M. Schott, S.G. Parker. Poster Session of the 1st High-Performance Graphics Conference, 2009.
An analytical approach to solving anisotropic single scattering from point light sources in homogeneous media was recently derived via a dual-formulation of the air-light integral. In this paper, we demonstrate how to reduce the evaluation of the terms involved in the solution and provide an efficient and practical implementation substantially increasing the real-time performance characteristics.
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A Directional Occlusion Shading Model for Interactive Direct Volume Rendering. M. Schott, V. Pegoraro, C.D. Hansen, K. Boulanger, K. Bouatouch. In Computer Graphics Forum (Proceedings of Eurographics/IEEE VGTC Symposium on Visualization 2009), Berlin, Germany, Vol. 28, No. 3, pp. 855--862. 2009.
Volumetric rendering is widely used to examine 3D scalar fields from CT/MRI scanners and numerical simulation datasets. One key aspect of volumetric rendering is the ability to provide perceptual cues to aid in understanding structure contained in the data. While shading models that reproduce natural lighting conditions have been shown to better convey depth information and spatial relationships, they traditionally require considerable (pre)computation. In this paper, a shading model for interactive direct volume rendering is proposed that provides perceptual cues similar to those of ambient occlusion, for both solid and transparent surface-like features. An image space occlusion factor is derived from the radiative transport equation based on a specialized phase function. The method does not rely on any precomputation and thus allows for interactive explorations of volumetric data sets via on-the-fly editing of the shading model parameters or (multi-dimensional) transfer functions while modifications to the volume via clipping planes are incorporated into the resulting occlusion-based shading.
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A Bayesian Monte Carlo Approach to Global Illumination. J. Brouillat, C. Bouville, B. Loos, C.D. Hansen, K. Bouatouch. In Computer Graphics Forum Journal, Early View, October, 2009.
Most Monte Carlo rendering algorithms rely on importance sampling to reduce the variance of estimates. Importance sampling is efficient when the proposal sample distribution is well-suited to the form of the integrand but fails otherwise. The main reason is that the sample location information is not exploited. All sample values are given the same importance regardless of their proximity to one another. Two samples falling in a similar location will have equal importance whereas they are likely to contain redundant information. The Bayesian approach we propose in this paper uses both the location and value of the data to infer an integral value based on a prior probabilistic model of the integrand. The Bayesian estimate depends only on the sample values and locations, and not how these samples have been chosen. We show how this theory can be applied to the final gathering problem and present results that clearly demonstrate the benefits of Bayesian Monte Carlo. |
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