EGSR07: 18th Eurographics Symposium on Rendering
Permanent URI for this collection
The Random Camera, the Coded Aperture Camera, and Other Cameras
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Freeman, William T.
Large-Scale Data Management for PRT-Based Real-Time Rendering of Dynamically Skinned Models
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Feng, Wei-Wen
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Peng, Liang
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Jia, Yuntao
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Yu, Yizhou
Precomputed Radiance Transfer for Real-time Indirect Lighting using a Spectral Mesh Basis
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Wang, Rui
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Zhu, Jiajun
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Humphreys, Greg
Precomputed Radiance Transfer for Dynamic Scenes Taking into Account Light Interreflection
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Iwasaki, Kei
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Dobashi, Yoshinori
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Yoshimoto, Fujiichi
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Nishita, Tomoyuki
Convolution Shadow Maps
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Annen, Thomas
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Mertens, Tom
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Bekaert, Philippe
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Seidel, Hans-Peter
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Kautz, Jan
Pixel-Correct Shadow Maps with Temporal Reprojection and Shadow Test Confidence
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Scherzer, Daniel
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Jeschke, Stefan
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Wimmer, Michael
Interactive Illumination with Coherent Shadow Maps
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Ritschel, Tobias
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Grosch, Thorsten
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Kautz, Jan
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Mueller, Stefan
Ray Tracing Dynamic Scenes using Selective Restructuring
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Yoon, Sung-Eui
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Curtis, Sean
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Manocha, Dinesh
A Real-time Beam Tracer with Application to Exact Soft Shadows
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Overbeck, Ryan
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Ramamoorthi, Ravi
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Mark, William R.
Whitted Ray-Tracing for Dynamic Scenes using a Ray-Space Hierarchy on the GPU
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Roger, David
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Assarsson, Ulf
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Holzschuch, Nicolas
Instant Sound Scattering
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Tsingos, Nicolas
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Dachsbacher, Carsten
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Lefebvre, Sylvain
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Dellepiane, Matteo
Scene Collages and Flexible Camera Arrays
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Nomura, Yoshikuni
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Zhang, Li
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Nayar, Shree K.
Efficient Rendering of Human Skin
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d'Eon, Eugene
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Luebke, David
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Enderton, Eric
Dynamic Point Distribution for Stroke-based Rendering
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Vanderhaeghe, David
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Barla, Pascal
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Thollot, Joelle
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Sillion, Francois X.
Dirty Glass: Rendering Contamination on Transparent Surfaces
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Gu, Jinwei
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Ramamoorthi, Ravi
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Belhumeur, Peter
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Nayar, Shree
Material Based Splashing of Water Drops
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Garg, Kshitiz
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Krishnan, Gurunandan G.
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Nayar, Shree K.
Rapid Acquisition of Specular and Diffuse Normal Maps from Polarized Spherical Gradient Illumination
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Ma, Wan-Chun
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Hawkins, Tim
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Peers, Pieter
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Chabert, Charles-Felix
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Weiss, Malte
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Debevec, Paul
Microfacet Models for Refraction through Rough Surfaces
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Walter, Bruce
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Marschner, Stephen R.
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Li, Hongsong
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Torrance, Kenneth E.
Efficient Basis Decomposition for Scattered Reflectance Data
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Weistroffer, R. Peter
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Walcott, Kristen R.
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Humphreys, Greg
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Lawrence, Jason
Procedural Editing of Bidirectional Texture Functions
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Mueller, Gero
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Sarlette, Ralf
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Klein, Reinhard
Rendering Discrete Random Media Using Precomputed Scattering Solutions
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Moon, Jonathan T.
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Walter, Bruce
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Marschner, Stephen R.
Rendering Translucent Materials Using Photon Diffusion
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Donner, Craig
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Jensen, Henrik Wann
Physically Based Real-Time Translucency for Leaves
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Habel, Ralf
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Kusternig, Alexander
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Wimmer, Michael
Photorealistic Image Rendering with Population Monte Carlo Energy Redistribution
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Lai, Yu-Chi
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Fan, Shao Hua
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Chenney, Stephen
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Dyer, Charcle
Incremental Instant Radiosity for Real-Time Indirect Illumination
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Laine, Samuli
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Saransaari, Hannu
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Kontkanen, Janne
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Lehtinen, Jaakko
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Aila, Timo
Soft Shadows by Ray Tracing Multilayer Transparent Shadow Maps
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Xie, Feng
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Tabellion, Eric
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Pearce, Andrew
An Interactive Perceptual Rendering Pipeline using Contrast and Spatial Masking
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Drettakis, George
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Bonneel, Nicolas
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Dachsbacher, Carsten
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Lefebvre, Sylvain
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Schwarz, Michael
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Viaud-Delmon, Isabelle
Natural Image Colorization
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Luan, Qing
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Wen, Fang
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Cohen-Or, Daniel
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Liang, Lin
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Xu, Ying-Qing
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Shum, Heung-Yeung
High Dynamic Range Image Hallucination
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Wang, Lvdi
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Wei, Li-Yi
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Zhou, Kun
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Guo, Baining
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Shum, Heung-Yeung
Using Photographs to Enhance Videos of a Static Scene
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Bhat, Pravin
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Zitnick, C. Lawrence
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Snavely, Noah
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Agarwala, Aseem
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Agrawala, Maneesh
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Cohen, Michael
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Curless, Brian
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Kang, Sing Bing
Compressed Random-Access Trees for Spatially Coherent Data
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Lefebvre, Sylvain
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Hoppe, Hugues
Interactive Smooth and Curved Shell Mapping
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Jeschke, Stefan
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Mantler, Stephan
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Wimmer, Michael
Feature-Guided Dynamic Texture Synthesis on Continuous Flows
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Narain, Rahul
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Kwatra, Vivek
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Lee, Huai-Ping
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Kim, Theodore
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Carlson, Mark
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Lin, Ming C.
Browse
Recent Submissions
Item The Random Camera, the Coded Aperture Camera, and Other Cameras(The Eurographics Association, 2007) Freeman, William T.; Jan Kautz and Sumanta PattanaikI ll describe two cameras and a comparison of many cameras. In the random camera, we use a lens which creates a pseudo-random relationship between incoming light rays and resulting sensor locations. We studied various properties (both good and bad) of the resulting camera and have built a prototype. The coded aperture camera is a conventional SLR camera but with a coded pattern of holes in the aperture. This gives a depthdependent blur which is both easy to identify and easy to deblur, allowing us to estimate, from the captured image, both an all-focus image and (roughly) the depth everywhere. Finally, we analyze cameras as linear projections of the 4-d lightfield and develop a Bayesian framework to study how well any given camera can recover the incident lightfield from its data. This gives a common framework in which to compare the performance of ordinary lenses, stereo cameras, random cameras, lenticular arrays, pinhole cameras, coded aperture cameras, etc. Joint work with Frédo Durand, Rob Fergus, Anat Levin, and Antonio Torralba.Item Global Illumination for the Masses(The Eurographics Association, 2007) Gatenby, Neil; Jan Kautz and Sumanta PattanaikGlobal Illumination (GI) algorithms came to fruition in the Graphics labs of USA, Europe, Japan, and beyond, during the 1980s and 1990s. The researchers who developed the algorithms had expert knowledge of the underlying physics, and an even more expert knowledge of how their own software behaved (and misbehaved!). Ten years ago, only the most specialised applications contained GI rendering algorithms those targetted at architects, or automotive manufacturers, or digital imagery for movies/advertising. The number of seats was always small, and the price per seat was always large. Radiosity, ray tracing and photon mapping, final gathering, irradiance caches and the use of MC and QMC importance sampling may all appear on an undergraduate graphics course in 2007, but they are still not the kind of thing one overhears being discussed in the average public house, or cafe! Yet today, it is hard to find AEC or MCAD software that does not contain such algorithms. Many of the public houses and cafes where the algorithms are not discussed contain customers who have kitchen (or bathroom, or garden) design software on their PC/Mac at home. They might not use it very often, nor explore its limits when they do use it, but use it they do. There are many millions of such users, and none of them has paid very much for the software in question. This talk will discuss the difficulties and opportunities that arise when designing GI software for such a market place, and will outline some of the shortcuts and tricks that are commonly employed by those writing the code.Item Large-Scale Data Management for PRT-Based Real-Time Rendering of Dynamically Skinned Models(The Eurographics Association, 2007) Feng, Wei-Wen; Peng, Liang; Jia, Yuntao; Yu, Yizhou; Jan Kautz and Sumanta PattanaikComputer games and real-time applications frequently adopt mesh skinning as a deformation technique for virtual characters and articulated objects. Rendering skinned models with global shading effects, such as interreflection and subsurface scattering, using precomputed radiance transfer enables high-quality real-time display of dynamically deformed objects. In this approach, we need to precompute radiance transfer for many sampled poses. Resulting datasets reach hundreds of gigabytes, and are orders of magnitude larger than those for a static object. This paper presents simple but effective large-scale data management techniques so that runtime data communication, decompression and interpolation can be performed efficiently and accurately. Specifically, we have developed a mesh clustering technique based on spectral graph partitioning to facilitate interpolation from nearest neighbors and an incremental clustering method for transfer matrix compression. By exploiting additional data redundancies among different sampled poses, we can achieve higher compression ratios with the same fidelity. Our incremental clustering can make the runtime cost of per-frame data decompression and interpolation satisfy a prescribed upper bound. As a result, we can achieve real-time performance using the massive precomputed data and an efficient runtime algorithm.Item Precomputed Radiance Transfer for Real-time Indirect Lighting using a Spectral Mesh Basis(The Eurographics Association, 2007) Wang, Rui; Zhu, Jiajun; Humphreys, Greg; Jan Kautz and Sumanta PattanaikSimulating indirect lighting effects has been a challenging topic in many real-time rendering and design applications. This paper presents a novel method, based on precomputed radiance transfer, for rendering physically based, multi-bounce indirect lighting in real-time. Our key idea is to represent both the direct lighting and precomputed diffuse indirect transfer using a spectral mesh basis set derived from an arbitrary scene model [KG00]. The complete spectral basis set can approximate a spatially varying function to any degree of accuracy. For indirect lighting, we show that only 60 ~ 100 sparse basis coefficients suffice to achieve high accuracy, due to the low-frequency nature of indirect illumination. This reduces the run-time computation of per-vertex diffuse indirect lighting to simple inner products of two sparse vectors: one representing the dynamic direct lighting, and the other representing the precomputed direct to indirect transfer. The key advantage using this approach is that we are not restricted to parameterized models or any particular mesh topology. Our method simulates multiple diffuse interreflections while at the same time permitting dynamically changing surface albedos. In addition, we approximate the final bounce of glossy interreflection using a standard BRDF SH projection. Finally, we demonstrate high-quality indirect lighting effects rendered at 15 ~ 30 fps with dynamically changing lighting and materials.Item Precomputed Radiance Transfer for Dynamic Scenes Taking into Account Light Interreflection(The Eurographics Association, 2007) Iwasaki, Kei; Dobashi, Yoshinori; Yoshimoto, Fujiichi; Nishita, Tomoyuki; Jan Kautz and Sumanta PattanaikFast rendering of dynamic scenes taking into account global illumination is one of the most challenging tasks in computer graphics. This paper proposes a new precomputed radiance transfer (PRT) method for rendering dynamic scenes of rigid objects taking into account interreflections of light between surfaces with diffuse and glossy BRDFs. To compute the interreflections of light between rigid objects, we consider the objects as secondary light sources. We represent the intensity distributions on the surface of the objects with a linear combination of basis functions. We then calculate a component of the irradiance per basis function at each vertex of the object when illuminated by the secondary light source. We call this component of the irradiance, the basis irradiance. The irradiance is represented with a linear combination of the basis irradiances, which are computed efficiently at run-time by using a PRT technique. By using the basis irradiance, the calculation of multiple-bounce interreflected light is simplified and can be evaluated very quickly. We demonstrate the real-time rendering of dynamic scenes for low-frequency lighting and rendering for all-frequency lighting at interactive frame rates.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 Pixel-Correct Shadow Maps with Temporal Reprojection and Shadow Test Confidence(The Eurographics Association, 2007) Scherzer, Daniel; Jeschke, Stefan; Wimmer, Michael; Jan Kautz and Sumanta PattanaikShadow mapping suffers from spatial aliasing (visible as blocky shadows) as well as temporal aliasing (visible as flickering). Several methods have already been proposed for reducing such artifacts, but so far none is able to provide satisfying results in real time. This paper extends shadow mapping by reusing information of previously rasterized images, stored efficiently in a so-called history buffer. This buffer is updated in every frame and then used for the shadow calculation. In combination with a special confidence-based method for the history buffer update (based on the current shadow map), temporal and spatial aliasing can be completely removed. The algorithm converges in about 10 to 60 frames and during convergence, shadow borders are sharpened over time. Consequently, in case of real-time frame rates, the temporal shadow adaption is practically imperceptible. The method is simple to implement and is as fast as uniform shadow mapping, incurring only the minor speed hit of the history buffer update. It works together with advanced filtering methods like percentage closer filtering and more advanced shadow mapping techniques like perspective or light space perspective shadow maps.Item Interactive Illumination with Coherent Shadow Maps(The Eurographics Association, 2007) Ritschel, Tobias; Grosch, Thorsten; Kautz, Jan; Mueller, Stefan; Jan Kautz and Sumanta PattanaikWe present a new method for interactive illumination computations based on precomputed visibility using coherent shadow maps (CSMs). It is well-known that visibility queries dominate the cost of physically based rendering. Precomputing all visibility events, for instance in the form of many shadow maps, enables fast queries and allows for real-time computation of illumination but requires prohibitive amounts of storage. We propose a lossless compression scheme for visibility information based on shadow maps that efficiently exploits coherence. We demonstrate a Monte Carlo renderer for direct lighting using CSMs that runs entirely on graphics hardware. We support spatially varying BRDFs, normal maps, and environment maps all with high frequencies, spatial as well as angular. Multiple dynamic rigid objects can be combined in a scene. As opposed to precomputed radiance transfer techniques, that assume distant lighting, our method includes distant lighting as well as local area lights of arbitrary shape, varying intensity, or anisotropic light distribution that can freely vary over time.Item Ray Tracing Dynamic Scenes using Selective Restructuring(The Eurographics Association, 2007) Yoon, Sung-Eui; Curtis, Sean; Manocha, Dinesh; Jan Kautz and Sumanta PattanaikWe present a novel algorithm to selectively restructure bounding volume hierarchies (BVHs) for ray tracing dynamic scenes. We derive two new metrics to evaluate the culling efficiency and restructuring benefit of any BVH. Based on these metrics, we perform selective restructuring operations that efficiently reconstruct small portions of a BVH instead of the entire BVH. Our approach is general and applicable to complex and dynamic scenes, including topological changes. We use the selective restructuring algorithm to improve the performance of ray tracing dynamic scenes that consist of hundreds of thousands of triangles. In our benchmarks, we observe up to an order of magnitude improvement over prior BVH-based ray tracing algorithms.Item A Real-time Beam Tracer with Application to Exact Soft Shadows(The Eurographics Association, 2007) Overbeck, Ryan; Ramamoorthi, Ravi; Mark, William R.; Jan Kautz and Sumanta PattanaikEfficiently calculating accurate soft shadows cast by area light sources remains a difficult problem. Ray tracing based approaches are subject to noise or banding, and most other accurate methods either scale poorly with scene geometry or place restrictions on geometry and/or light source size and shape. Beam tracing is one solution which has historically been considered too slow and complicated for most practical rendering applications. Beam tracing s performance has been hindered by complex geometry intersection tests, and a lack of good acceleration structures with efficient algorithms to traverse them. We introduce fast new algorithms for beam tracing, specifically for beam triangle intersection and beam kd-tree traversal. The result is a beam tracer capable of calculating precise primary visibility and point light shadows in real-time. Moreover, beam tracing provides full area elements instead of point samples, which allows us to maintain coherence through to secondary effects and utilize the GPU for high quality antialiasing and shading with minimal extra cost. More importantly, our analysis shows that beam tracing is particularly well suited to soft shadows from area lights, and we generate essentially exact noise-free soft shadows for complex scenes in seconds rather than minutes or hours.Item Whitted Ray-Tracing for Dynamic Scenes using a Ray-Space Hierarchy on the GPU(The Eurographics Association, 2007) Roger, David; Assarsson, Ulf; Holzschuch, Nicolas; Jan Kautz and Sumanta PattanaikIn this paper, we present a new algorithm for interactive rendering of animated scenes with Whitted Ray-Tracing, running on the GPU. We focus our attention on the secondary rays (the rays generated by one or more bounces on specular objects), and use the GPU rasterizer for primary rays. Our algorithm is based on a ray-space hierarchy, allowing us to handle truly dynamic scenes without the need to rebuild or update the scene hierarchy. The rayspace hierarchy is entirely built on the GPU for every frame, using a very fast process. Traversing the ray-space hierarchy is also done on the GPU; one of the benefits of using a ray-space hierarchy is that we have a single shader, and a fixed number of passes. After traversing each level of the hierarchy, we prune empty branches using a stream reduction method. We present two different stream reduction methods, a fast one using a hierarchical algorithm, and an easy one using the Geometry shaders. Our algorithm results in interactive rendering with specular reflections and shadows for moderately complex scenes (~ 700K triangles), handles any kind of dynamic or unstructured scenes without any pre-processing, and scales well with both the scene complexity and the image resolution.Item General Linear Cameras with Finite Aperture(The Eurographics Association, 2007) Adams, Andrew; Levoy, Marc; Jan Kautz and Sumanta PattanaikA pinhole camera selects a two-dimensional set of rays from the four-dimensional light field. Pinhole cameras are a type of general linear camera, defined as planar 2D slices of the 4D light field. Cameras with finite apertures can be considered as the summation of a collection of pinhole cameras. In the limit they evaluate a two-dimensional integral of the four-dimensional light field. Hence a general linear camera with finite aperture factors the 4D light field into two integrated dimensions and two imaged dimensions. We present a simple framework for representing these slices and integral projections, based on certain eigenspaces in a two-plane parameterization of the light field. Our framework allows for easy analysis of focus and perspective, and it demonstrates their dual nature. Using our framework, we present analogous taxonomies of perspective and focus, placing within them the familiar perspective, orthographic, cross-slit, and bilinear cameras; astigmatic and anastigmatic focus; and several other varieties of perspective and focus.Item Instant Sound Scattering(The Eurographics Association, 2007) Tsingos, Nicolas; Dachsbacher, Carsten; Lefebvre, Sylvain; Dellepiane, Matteo; Jan Kautz and Sumanta PattanaikReal-time sound rendering engines often render occlusion and early sound reflection effects using geometrical techniques such as ray or beam tracing. They can only achieve interactive rendering for environments of low local complexity resulting in crude effects which can degrade the sense of immersion. However, surface detail or complex dynamic geometry has a strong influence on sound propagation and the resulting auditory perception. This paper focuses on high-quality modeling of first-order sound scattering. Based on a surface-integral formulation and the Kirchhoff approximation, we propose an efficient evaluation of scattering effects, including both diffraction and reflection, that leverages programmable graphics hardware for dense sampling of complex surfaces. We evaluate possible surface simplification techniques and show that combined normal and displacement maps can be successfully used for audio scattering calculations. We present an auralization framework that can render scattering effects interactively thus providing a more compelling experience. We demonstrate that, while only considering first order phenomena, our approach can provide realistic results for a number of practical interactive applications. It can also process highly detailed models containing millions of unorganized triangles in minutes, generating high-quality scattering filters. Resulting simulations compare well with on-site recordings showing that the Kirchhoff approximation can be used for complex scattering problems.Item Scene Collages and Flexible Camera Arrays(The Eurographics Association, 2007) Nomura, Yoshikuni; Zhang, Li; Nayar, Shree K.; Jan Kautz and Sumanta PattanaikThis paper presents an automatic method for creating a collage from a collection of photos of a scene taken from different viewpoints. The collage is constructed by aligning the images (in terms of their positions, rotations and scales) using a least-squares formulation. We have developed a graph-based optimization algorithm for layering the images so as to minimize the fragmentation of the collage. A collage can be displayed with opaque layers, with transparent layers, or with blended image boundaries. A scene collage can be viewed as a piece-wise perspective representation of a scene with visible seams. This representation has not only aesthetic value but also conveys scene structure and camera motion in an intuitive way. To capture live-action collages of dynamic scenes we have developed camera arrays that can be physically flexed by the user to continuously vary the composition of the scene. The design of our camera arrays enables a user to reconfigure them in terms of the spatial arrangement of the cameras in a matter of minutes. We show several still and dynamic examples that demonstrate that scene collages provide a new and interesting way to experience scenes.Item Efficient Rendering of Human Skin(The Eurographics Association, 2007) d'Eon, Eugene; Luebke, David; Enderton, Eric; Jan Kautz and Sumanta PattanaikExisting offline techniques for modeling subsurface scattering effects in multi-layered translucent materials such as human skin achieve remarkable realism, but require seconds or minutes to generate an image. We demonstrate rendering of multi-layer skin that achieves similar visual quality but runs orders of magnitude faster. We show that sums of Gaussians provide an accurate approximation of translucent layer diffusion profiles, and use this observation to build a novel skin rendering algorithm based on texture space diffusion and translucent shadow maps. Our technique requires a parameterized model but does not otherwise rely on any precomputed information, and thus extends trivially to animated or deforming models. We achieve about 30 frames per second for realistic real-time rendering of deformable human skin under dynamic lighting.Item Dynamic Point Distribution for Stroke-based Rendering(The Eurographics Association, 2007) Vanderhaeghe, David; Barla, Pascal; Thollot, Joelle; Sillion, Francois X.; Jan Kautz and Sumanta PattanaikWe present a new point distribution algorithm that is well adapted to stroke-based rendering systems. Its main characteristic is to deal efficiently with three conflicting constraints: the distribution of points should retain a good repartition in 2D; their motion should tightly follow the target motion in the underlying scene; and as few points as possible should be added or deleted from frame to frame. We show that previous methods fail to meet at least one of these constraints in the general case, as opposed to our approach that is independent of scene complexity and motion. As a result, our algorithm is able to take 3D scenes as well as videos as input and create non-uniform distributions with good temporal coherence and density properties. To illustrate it, we show applications in four different styles: stippling, pointillism, hatching and painterly.Item Dirty Glass: Rendering Contamination on Transparent Surfaces(The Eurographics Association, 2007) Gu, Jinwei; Ramamoorthi, Ravi; Belhumeur, Peter; Nayar, Shree; Jan Kautz and Sumanta PattanaikRendering of clean transparent objects has been well studied in computer graphics. However, real-world transparent objects are seldom clean their surfaces have a variety of contaminants such as dust, dirt, and lipids. These contaminants produce a number of complex volumetric scattering effects that must be taken into account when creating photorealistic renderings. In this paper, we take a step toward modeling and rendering these effects. We make the assumption that the contaminant is an optically thin layer and construct an analytic model following results in radiative transport theory and computer graphics. Moreover, the spatial textures created by the different types of contamination are also important in achieving visual realism. To this end, we measure the spatially varying thicknesses and the scattering parameters of a number of glass panes with various types of dust, dirt, and lipids. We also develop a simple interactive synthesis tool to create novel instances of the measured contamination patterns. We show several results that demonstrate the use of our scattering model for rendering 3D scenes, as well as modifying real 2D photographs.Item Material Based Splashing of Water Drops(The Eurographics Association, 2007) Garg, Kshitiz; Krishnan, Gurunandan G.; Nayar, Shree K.; Jan Kautz and Sumanta PattanaikThe splashing of a water drop is a fascinating phenomenon that results from a variety of complex interactions between the drop and the material it impacts. In general, the distribution of droplets of a splash depends on the drop size and velocity; the surface roughness, rigidity, and wetness; and the angle of impact. Given the number of factors involved, it is difficult to develop an analytical model for the splash distribution. Instead, we take an empirical approach. We have measured the splashing behaviors of 22 different materials that are commonly found in the real world. These materials can be broadly classified as rough (e.g., wood and brick), smooth (e.g., marble and glass), flexible (e.g., silk and paper), and miscellaneous (e.g., water and moss). We have developed a stochastic model for splash distribution that builds upon empirical models previously developed in fluid dynamics and meteorology. Our model is simple and only requires 7 coefficients for generating splashes for head-on impact for a material. A more general model for generating splashes for arbitrary impact angles (due to surface inclination or wind) requires 54 coefficients. The models of different materials may be combined to generate physically plausible splashes for novel materials that have not been measured. Our model is applicable for rendering splashes due to rain as well as water drops falling from large heights such as windowsills, trees, and rooftops.Item Rapid Acquisition of Specular and Diffuse Normal Maps from Polarized Spherical Gradient Illumination(The Eurographics Association, 2007) Ma, Wan-Chun; Hawkins, Tim; Peers, Pieter; Chabert, Charles-Felix; Weiss, Malte; Debevec, Paul; Jan Kautz and Sumanta PattanaikWe estimate surface normal maps of an object from either its diffuse or specular reflectance using four spherical gradient illumination patterns. In contrast to traditional photometric stereo, the spherical patterns allow normals to be estimated simultaneously from any number of viewpoints. We present two polarized lighting techniques that allow the diffuse and specular normal maps of an object to be measured independently. For scattering materials, we show that the specular normal maps yield the best record of detailed surface shape while the diffuse normals deviate from the true surface normal due to subsurface scattering, and that this effect is dependent on wavelength. We show several applications of this acquisition technique. First, we capture normal maps of a facial performance simultaneously from several viewing positions using time-multiplexed illumination. Second, we show that highresolution normal maps based on the specular component can be used with structured light 3D scanning to quickly acquire high-resolution facial surface geometry using off-the-shelf digital still cameras. Finally, we present a realtime shading model that uses independently estimated normal maps for the specular and diffuse color channels to reproduce some of the perceptually important effects of subsurface scattering.Item Microfacet Models for Refraction through Rough Surfaces(The Eurographics Association, 2007) Walter, Bruce; Marschner, Stephen R.; Li, Hongsong; Torrance, Kenneth E.; Jan Kautz and Sumanta PattanaikMicrofacet models have proven very successful for modeling light reflection from rough surfaces. In this paper we review microfacet theory and demonstrate how it can be extended to simulate transmission through rough surfaces such as etched glass. We compare the resulting transmission model to measured data from several real surfaces and discuss appropriate choices for the microfacet distribution and shadowing-masking functions. Since rendering transmission through media requires tracking light that crosses at least two interfaces, good importance sampling is a practical necessity. Therefore, we also describe efficient schemes for sampling the microfacet models and the corresponding probability density functions.Item Efficient Basis Decomposition for Scattered Reflectance Data(The Eurographics Association, 2007) Weistroffer, R. Peter; Walcott, Kristen R.; Humphreys, Greg; Lawrence, Jason; Jan Kautz and Sumanta PattanaikRecent progress in acquisition technology has increased the availability and quality of measured appearance data. Although representations based on dimensionality reduction provide the greatest fidelity to measured data, they require assembling a high-resolution and regularly sampled matrix from sparse and non-uniformly scattered input. Constructing and processing this immense matrix becomes a significant computational bottleneck. We describe a technique for performing basis decomposition directly from scattered measurements. Our approach is flexible in how the basis is represented and can accommodate any number of linear constraints on the factorization. Because its time- and space-complexity is proportional to the number of input measurements and the size of the output, we are able to decompose multi-gigabyte datasets faster and at lower error rates than currently available techniques. We evaluate our approach by representing measured spatially-varying reflectance within a reduced linear basis defined over radial basis functions and a database of measured BRDFs.Item Procedural Editing of Bidirectional Texture Functions(The Eurographics Association, 2007) Mueller, Gero; Sarlette, Ralf; Klein, Reinhard; Jan Kautz and Sumanta PattanaikMeasured material representations like Bidirectional Texture Functions or Reflectance Fields offer very realistic appearance but the user is currently not capable of changing this appearance in an effective and intuitive way. Such editing operations would require a low-dimensional but expressive model for appearance that exposes only a small set of intuitively editable parameters (1D-sliders, 2D-maps) to the user but preserves all visually relevant details. In this paper we present a novel editing technique for complex spatially varying materials. It is based on the observation that we are already good in modeling the basic geometric structure of many natural and manmade materials but still have not found effective models for the detailed small-scale geometry and the interaction of light with these materials. Our main idea is to use procedural geometry to define the basic structure of a material and then to enrich this structure with the BTF information captured from real materials. By employing recent algorithms for real-time texture synthesis and BTF compression our technique allows interactive editing.Item Rendering Discrete Random Media Using Precomputed Scattering Solutions(The Eurographics Association, 2007) Moon, Jonathan T.; Walter, Bruce; Marschner, Stephen R.; Jan Kautz and Sumanta PattanaikThis paper addresses light transport through a discrete random medium, which we define as a volume filled with macroscopic scattering geometry generated by a random process. This formulation is more general than standard radiative transport, because it can be applied to media that are made up of closely packed scatterers. A new approach to rendering these media is introduced, based on precomputed solutions to a local multiple scattering problem, including a new algorithm for generating paths through random media that moves through the interior of the medium in large strides without considering individual scattering events. A method for rendering homogeneous isotropic random media is described that generates paths using precomputed scattering solutions compressed and randomly sampled using Nonnegative Matrix Factorization. It can efficiently render discrete media, such as a large pile of glass objects, in which the individual scatterers are visible. The method is demonstrated on scenes containing tens of thousands of transparent, specular objects that are nearly impossible to render with standard global illumination techniques.Item Rendering Translucent Materials Using Photon Diffusion(The Eurographics Association, 2007) Donner, Craig; Jensen, Henrik Wann; Jan Kautz and Sumanta PattanaikWe present a new algorithm for rendering translucent materials that combines photon tracing with diffusion. This combination makes it possible to efficiently render highly scattering translucent materials while accounting for internal blockers, complex geometry, translucent inter-scattering, and transmission and refraction of light at the boundary causing internal caustics. These effects cannot be accounted for with previous rendering approaches using the dipole or multipole diffusion approximations that only sample the incident illumination at the surface of the material. Instead of sampling lighting at the surface we trace photons into the material and store them volumetrically at their first scattering interaction with the material. We hierarchically integrate the diffusion of light from the photons to compute the radiant emittance at points on the surface of the material. For increased accuracy we use the incidence plane of the photon and the viewpoint on the surface to blend between three analytic diffusion approximations that best describe the geometric configuration between the photon and the shading point. For this purpose we introduce a new quadpole diffusion approximation that models diffusion at right angled edges, and an attenuation kernel to more accurately model multiple scattering near a light source. The photon diffusion approach is as efficient as previous Monte Carlo sampling approaches based on the dipole or multipole diffusion approximations, and our results demonstrate that it is more accurate and capable of capturing several illumination effects previously ignored when simulating the diffusion of light in translucent materials.Item Physically Based Real-Time Translucency for Leaves(The Eurographics Association, 2007) Habel, Ralf; Kusternig, Alexander; Wimmer, Michael; Jan Kautz and Sumanta PattanaikThis paper presents a new shading model for real-time rendering of plant leaves that reproduces all important attributes of a leaf and allows for a large number of leaves to be shaded. In particular, we use a physically based model for accurate subsurface scattering on the translucent side of directly lit leaves. For real-time rendering of this model, we formulate it as an image convolution process and express the result in an efficient directional basis that is fast to evaluate. We also propose a data acquisition method for leaves that uses off-the-shelf devices.Item Photorealistic Image Rendering with Population Monte Carlo Energy Redistribution(The Eurographics Association, 2007) Lai, Yu-Chi; Fan, Shao Hua; Chenney, Stephen; Dyer, Charcle; Jan Kautz and Sumanta PattanaikThis work presents a novel global illumination algorithm which concentrates computation on important light transport paths and automatically adjusts energy distributed area for each light transport path. We adapt statistical framework of Population Monte Carlo into global illumination to improve rendering efficiency. Information collected in previous iterations is used to guide subsequent iterations by adapting the kernel function to approximate the target distribution without introducing bias into the final result. Based on this framework, our algorithm automatically adapts the amount of energy redistribution at different pixels and the area over which energy is redistributed. Our results show that the efficiency can be improved by exploring the correlated information among light transport paths.Item Incremental Instant Radiosity for Real-Time Indirect Illumination(The Eurographics Association, 2007) Laine, Samuli; Saransaari, Hannu; Kontkanen, Janne; Lehtinen, Jaakko; Aila, Timo; Jan Kautz and Sumanta PattanaikWe present a method for rendering single-bounce indirect illumination in real time on currently available graphics hardware. The method is based on the instant radiosity algorithm, where virtual point lights (VPLs) are generated by casting rays from the primary light source. Hardware shadow maps are then employed for determining the indirect illumination from the VPLs. Our main contribution is an algorithm for reusing the VPLs and incrementally maintaining their good distribution. As a result, only a few shadow maps need to be rendered per frame as long as the motion of the primary light source is reasonably smooth. This yields real-time frame rates even when hundreds of VPLs are used.Item Soft Shadows by Ray Tracing Multilayer Transparent Shadow Maps(The Eurographics Association, 2007) Xie, Feng; Tabellion, Eric; Pearce, Andrew; Jan Kautz and Sumanta PattanaikWe present a method for high quality soft shadows for area lights in cinematic lighting. The method is an extension of traditional shadow maps, so it has the advantage of image based shadow methods; the algorithm s complexity is independent of geometric complexity. We introduce multilayer transparent shadow maps, which can be used to produce high quality soft shadows for scenes with extremely complex geometry, fur, and volume objects. Instead of the traditional sampling and filtering of shadow maps, we compute the shadow factor by ray tracing the multilayer transparent shadow map. The result is soft shadows of quality similar to that achieved by stochastic ray tracing, but at a much lower cost.Item An Interactive Perceptual Rendering Pipeline using Contrast and Spatial Masking(The Eurographics Association, 2007) Drettakis, George; Bonneel, Nicolas; Dachsbacher, Carsten; Lefebvre, Sylvain; Schwarz, Michael; Viaud-Delmon, Isabelle; Jan Kautz and Sumanta PattanaikWe present a new perceptual rendering pipeline which takes into account visual masking due to contrast and spatial frequency. Our framework predicts inter-object, scene-level masking caused by partial occlusion and shadows. It is designed for interactive applications and runs efficiently on the GPU. This is achieved using a layer-based approach together with an efficient GPU-based computation of threshold maps. We build upon this prediction framework to introduce a perceptually-based level of detail control algorithm. We conducted a perceptual user study which indicates that our perceptual pipeline generates results which are consistent with what the user perceives. Our results demonstrate significant quality improvement for scenes with masking due to frequencies and contrast, such as masking due to trees or foliage, or due to high-frequency shadows.Item Natural Image Colorization(The Eurographics Association, 2007) Luan, Qing; Wen, Fang; Cohen-Or, Daniel; Liang, Lin; Xu, Ying-Qing; Shum, Heung-Yeung; Jan Kautz and Sumanta PattanaikIn this paper, we present an interactive system for users to easily colorize the natural images of complex scenes. In our system, colorization procedure is explicitly separated into two stages: Color labeling and Color mapping. Pixels that should roughly share similar colors are grouped into coherent regions in the color labeling stage, and the color mapping stage is then introduced to further fine-tune the colors in each coherent region. To handle textures commonly seen in natural images, we propose a new color labeling scheme that groups not only neighboring pixels with similar intensity but also remote pixels with similar texture. Motivated by the insight into the complementary nature possessed by the highly contrastive locations and the smooth locations, we employ a smoothness map to guide the incorporation of intensity-continuity and texture-similarity constraints in the design of our labeling algorithm. Within each coherent region obtained from the color labeling stage, the color mapping is applied to generate vivid colorization effect by assigning colors to a few pixels in the region. A set of intuitive interface tools is designed for labeling, coloring and modifying the result. We demonstrate compelling results of colorizing natural images using our system, with only a modest amount of user input.Item High Dynamic Range Image Hallucination(The Eurographics Association, 2007) Wang, Lvdi; Wei, Li-Yi; Zhou, Kun; Guo, Baining; Shum, Heung-Yeung; Jan Kautz and Sumanta PattanaikWe introduce high dynamic range image hallucination for adding high dynamic range details to the over-exposed and under-exposed regions of a low dynamic range image. Our method is based on a simple assumption: there exist high quality patches in the image with similar textures as the regions that are over or under exposed. Hence, we can add high dynamic range details to a region by simply transferring texture details from another patch that may be under different illumination levels. In our approach, a user only needs to annotate the image with a few strokes to indicate textures that can be applied to the corresponding under-exposed or over-exposed regions, and these regions are automatically hallucinated by our algorithm. Experiments demonstrate that our simple, yet effective approach is able to significantly increase the amount of texture details in a wide range of common scenarios, with a modest amount of user interaction.Item Using Photographs to Enhance Videos of a Static Scene(The Eurographics Association, 2007) Bhat, Pravin; Zitnick, C. Lawrence; Snavely, Noah; Agarwala, Aseem; Agrawala, Maneesh; Cohen, Michael; Curless, Brian; Kang, Sing Bing; Jan Kautz and Sumanta PattanaikWe present a framework for automatically enhancing videos of a static scene using a few photographs of the same scene. For example, our system can transfer photographic qualities such as high resolution, high dynamic range and better lighting from the photographs to the video. Additionally, the user can quickly modify the video by editing only a few still images of the scene. Finally, our system allows a user to remove unwanted objects and camera shake from the video. These capabilities are enabled by two technical contributions presented in this paper. First, we make several improvements to a state-of-the-art multiview stereo algorithm in order to compute view-dependent depths using video, photographs, and structure-from-motion data. Second, we present a novel image-based rendering algorithm that can re-render the input video using the appearance of the photographs while preserving certain temporal dynamics such as specularities and dynamic scene lighting.Item Compressed Random-Access Trees for Spatially Coherent Data(The Eurographics Association, 2007) Lefebvre, Sylvain; Hoppe, Hugues; Jan Kautz and Sumanta PattanaikAdaptive multiresolution hierarchies are highly efficient at representing spatially coherent graphics data. We introduce a framework for compressing such adaptive hierarchies using a compact randomly-accessible tree structure. Prior schemes have explored compressed trees, but nearly all involve entropy coding of a sequential traversal, thus preventing fine-grain random queries required by rendering algorithms. Instead, we use fixed-rate encoding for both the tree topology and its data. Key elements include the replacement of pointers by local offsets, a forested mipmap structure, vector quantization of inter-level residuals, and efficient coding of partially defined data. Both the offsets and codebook indices are stored as byte records for easy parsing by either CPU or GPU shaders. We show that continuous mipmapping over an adaptive tree is more efficient using primal subdivision than traditional dual subdivision. Finally, we demonstrate efficient compression of many data types including light maps, alpha mattes, distance fields, and HDR images.Item Interactive Smooth and Curved Shell Mapping(The Eurographics Association, 2007) Jeschke, Stefan; Mantler, Stephan; Wimmer, Michael; Jan Kautz and Sumanta PattanaikShell mapping is a technique to represent three-dimensional surface details. This is achieved by extruding the triangles of an existing mesh along their normals, and mapping a 3D function (e.g., a 3D texture) into the resulting prisms. Unfortunately, such a mapping is nonlinear. Previous approaches perform a piece-wise linear approximation by subdividing the prisms into tetrahedrons. However, such an approximation often leads to severe artifacts. In this paper we present a correct (i.e., smooth) mapping that does not rely on a decomposition into tetrahedrons. We present an efficient GPU ray casting algorithm which provides correct parallax, self-occlusion, and silhouettes, at the cost of longer rendering times. The new formulation also allows modeling shells with smooth curvatures using Coons patches within the prisms. Tangent continuity between adjacent prisms is guaranteed, while the mapping itself remains local, i.e. every curved prism content is modeled at runtime in the GPU without the need for any precomputation. This allows instantly replacing animated triangular meshes with prism-based shells.Item Feature-Guided Dynamic Texture Synthesis on Continuous Flows(The Eurographics Association, 2007) Narain, Rahul; Kwatra, Vivek; Lee, Huai-Ping; Kim, Theodore; Carlson, Mark; Lin, Ming C.; Jan Kautz and Sumanta PattanaikWe present a technique for synthesizing spatially and temporally varying textures on continuous flows using image or video input, guided by the physical characteristics of the fluid stream itself. This approach enables the generation of realistic textures on the fluid that correspond to the local flow behavior, creating the appearance of complex surface effects, such as foam and small bubbles. Our technique requires only a simple specification of texture behavior, and automatically generates and tracks the features and texture over time in a temporally coherent manner. Based on this framework, we also introduce a technique to perform feature-guided video synthesis. We demonstrate our algorithm on several simulated and recorded natural phenomena, including splashing water and lava flows. We also show how our methodology can be extended beyond realistic appearance synthesis to more general scenarios, such as temperature-guided synthesis of complex surface phenomena in a liquid during boiling.