@article{weidlich-2009-dispersion, title = "Anomalous Dispersion in Predictive Rendering", author = "Andrea Weidlich and Alexander Wilkie", year = "2009", abstract = "In coloured media, the index of refraction does not decrease monotonically with increasing wavelength, but behaves in a quite non-monotonical way. This behaviour is called anomalous dispersion and results from the fact that the absorption of a material influences its index of refraction. So far, this interesting fact has not been widely acknowledged by the graphics community. In this paper, we demonstrate how to calculate the correct refractive index for a material based on its absorption spectrum with the Kramers-Kronig relation, and we discuss for which types of objects this effect is relevant in practice. ", month = jun, journal = "Computer Graphics Forum", volume = "28", number = "4", pages = "1065--1072", keywords = "Predictive rendering, Spectral Rendering, Dispersion", URL = "https://www.cg.tuwien.ac.at/research/publications/2009/weidlich-2009-dispersion/", } @article{wilkie-2009-cc, title = "A Robust Illumination Estimate for Chromatic Adaptation in Rendered Images", author = "Alexander Wilkie and Andrea Weidlich", year = "2009", abstract = "We propose a method that improves automatic colour correction operations for rendered images. In particular, we propose a robust technique for estimating the visible and pertinent illumination in a given scene. We do this at very low computational cost by mostly re-using information that is already being computed during the image synthesis process. Conventional illuminant estimations either operate only on 2D image data, or, if they do go beyond pure image analysis, only use information on the luminaires found in the scene. The latter is usually done with little or no regard for how the light sources actually affect the part of the scene that is being viewed. Our technique goes beyond that, and also takes object reflectance into account, as well as the incident light that is actually responsible for the colour of the objects that one sees. It is therefore able to cope with difficult cases, such as scenes with mixed illuminants, complex scenes with many light sources of varying colour, or strongly coloured indirect illumination. ", month = jun, journal = "Computer Graphics Forum", volume = "28", number = "4", pages = "1101--1109", keywords = "chromatic adaptation, predicitve rendering, colour constancy", URL = "https://www.cg.tuwien.ac.at/research/publications/2009/wilkie-2009-cc/", } @inproceedings{weidlich_2009_REL, title = "Rendering the Effect of Labradorescence", author = "Andrea Weidlich and Alexander Wilkie", year = "2009", abstract = "Labradorescence is a complex optical phenomenon that can be found in certain minerals, such as Labradorite or Spectrolite. Because of their unique colour properties these minerals are often used as gemstones and decorative objects. Since the phenomenon is strongly orientation dependent, such minerals need a special cut to make the most of their unique type of colourful sheen, which makes it desirable to be able to predict the final appearance of a given stone prior to the cutting process. Also, the peculiar properties of the effect make a believable replication with an ad-hoc shader dificult even for normal, non-predictive rendering purposes. We provide a reflectance model for labradorescence that is directly derived from the physical characteristics of such materials. Due to its inherent accuracy, it can be used for predictive rendering purposes, but also for generic rendering applications. ", month = may, isbn = "978-1-56881-470-4", publisher = "ACM", location = "Kelowna, British Columbia, Canada ", booktitle = "Proceedings of Graphics Interface 2009", pages = "79--85", keywords = "Predictive Rendering, Surface, Crystals", URL = "https://www.cg.tuwien.ac.at/research/publications/2009/weidlich_2009_REL/", } @phdthesis{weidlich-2009-thesis, title = "Pseudochromatic Colourisation of Crystals in Predictive Image Synthesis", author = "Andrea Weidlich", year = "2009", month = jan, address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", school = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", keywords = "Predictive rendering, Crystal rendering", URL = "https://www.cg.tuwien.ac.at/research/publications/2009/weidlich-2009-thesis/", } @inproceedings{weidlich_2009_EPLBM, title = "Exploring the Potential of Layered BRDF Models", author = "Andrea Weidlich and Alexander Wilkie", year = "2009", abstract = "This course serves as a guide on the considerable potential of layered surface models. The key advantage of using such layered BRDFs over traditional, more general shading language constructs is that the end result is automatically highly physically plausible. In particular, we demonstrate on a simple layered surface model that combines several traditional BRDF components how a surprisingly large number of interesting and important surface types can be efficiently represented by using the same, not particularly complex, BRDF code. We also show how handy such an approach is for the eventual end user, whose main concern is the ease with which one can describe object appearance based only on a few intuitive parameters. We first discuss layered surface models in computer graphics and the constraints of modelling object appearance in a physically plausible fashion. We then demonstrate the techniques that can be used to efficiently evaluate layered BRDF models, give examples of the surface types that can be described in this way. We also go beyond plain surface models, and showcase how a texture-based combination of layered surface components can be used to describe highly complex object appearance attributes, while implicitly remaining physically plausible.", booktitle = "SIGGRAPH Asia 2009 Courses", location = "Yokohama, Japan", publisher = "webpage: http://portal.acm.org/citation.cfm?id=1665824", URL = "https://www.cg.tuwien.ac.at/research/publications/2009/weidlich_2009_EPLBM/", } @inproceedings{wilkie-209.pr, title = "Predictive Rendering", author = "Alexander Wilkie and Andrea Weidlich and Marcus Magnor and A. Chalmers", year = "2009", abstract = "This course intends to serve two closely related purposes: to provide an accurate definition of the term predictive rendering, the sub-discipline of computer graphics that attempts to provide reliable predictions of object appearance, and to present the technological foundations on which one can currently conduct research in this area. The first goal of the course – a clear definition of what predictive rendering actually is – seems to be necessary due to the extreme prevalence of its antonym, believable rendering. Practically all contemporary production computer graphics, as well as most current graphics research efforts, fall into the latter category. Coupled with the fact that in the collective mindset of the graphics community, the distinction between these areas has, for a variety of reasons, been somewhat blurry so far, a precise clarifying statement appears to be in order. The second, much larger and technical part of the course then presents the foundations of current predictive rendering. Unlike believable rendering, where any technology that delivers visually convincing (as opposed to radiometrically correct) results is acceptable for a given task, a predictive pipeline suffers from the fundamental problem that all components – modeling, rendering, display – have to be of a uniformly high quality to ensure a predictive result. This fact has, over time, no doubt served to deter many researchers from entering this promising and interesting field, in which a large amount of work still lies ahead of us. In the second part, we cover an entire predictive rendering pipeline, and for each stage present those – in some cases surprisingly few – graphics technologies that can be used in such a context. This course should enable anyone with a solid background in graphics to bootstrap a basic predictive rendering environment, with which further research, or perhaps even specialised production work, can be conducted.", booktitle = "SIGGRAPH Asia 2009 Courses", location = "Yokohama, Japan", URL = "https://www.cg.tuwien.ac.at/research/publications/2009/wilkie-209.pr/", } @inproceedings{weidlich_2008_magwpt, title = "Modeling Aventurescent Gems with Procedural Textures", author = "Andrea Weidlich and Alexander Wilkie", year = "2008", abstract = "In this paper we present the results of an investigation on how one can model aventurescence, an interesting and optically appealing property of some gemstones. Our goal was to find a method that is both efficient and reasonably realistic, and that can still be used in the context of a global illumination rendering system.", month = apr, publisher = "ACM", location = "Budmarice", booktitle = "Proceedings of the Spring Conference on Computer Graphics (SCCG)", keywords = "gemstone rendering, aventurescence, procedural textures", URL = "https://www.cg.tuwien.ac.at/research/publications/2008/weidlich_2008_magwpt/", } @article{weidlich_2007_rrbuc, title = "Realistic Rendering of Birefringency in Uniaxial Crystals", author = "Andrea Weidlich and Alexander Wilkie", year = "2008", abstract = "In this paper we derive the complete set of formulas which is needed to generate physically plausible images of uniaxial crystals. So far no computer graphics publication contains all the formulas one needs to compute the interaction of light with such crystals in a form that is useable by a graphics application, especially if a polarisation-aware rendering system is being used. This paper contains the complete derivation of the Fresnel coefficients for birefringent transparent materials, as well as for the direction cosines of the extraordinary ray and the Mueller matrices necessary to describe polarisation effects. The formulas we derive can be directly used in a ray based renderer, and we demonstrate these capabilities in test scenes.", month = mar, journal = "ACM Transactions on Graphics", volume = "27", number = "1", pages = "6:1--6:12", keywords = "polarization, crystals, Birefringence", URL = "https://www.cg.tuwien.ac.at/research/publications/2008/weidlich_2007_rrbuc/", } @inproceedings{weidlich_2007_almfs, title = "Arbitrarily Layered Micro-Facet Surfaces", author = "Andrea Weidlich and Alexander Wilkie", year = "2007", abstract = "In this paper we present a method to combine several micro-facet based surface layers into a single unified, expressive BRDF model that is easy to use. The restriction to micro-facet based layers constitutes no loss of generality, since both perfectly specular and perfectly diffuse surfaces can be seen as limit cases of the micro-facet approach. Such multi-layered surfaces can be used to re-create the appearance of a wide range of different materials, and yield good results without having to perform explicit sub–surface scattering computations. This is achieved through suitable approximations and simplifications of the scattering within the simulated layered surface, while still taking absorption and total internal reflection into account. We also discuss the corresponding probability distribution function that is needed for sampling purposes, and investigate how the flexibility of this new approach is best put to use. ", month = dec, isbn = "978-1-59593-912-8", publisher = "ACM", location = "Perth, Australia", booktitle = "GRAPHITE 2007", pages = "171--178", URL = "https://www.cg.tuwien.ac.at/research/publications/2007/weidlich_2007_almfs/", } @inproceedings{wilkie-2006-dfs, title = "A Reflectance Model for Diffuse Fluorescent Surfaces", author = "Alexander Wilkie and Andrea Weidlich and Caroline Larboulette and Werner Purgathofer", year = "2006", abstract = "Fluorescence is an interesting and visually prominent effect, which has not been fully covered by Computer Graphics research so far. While the physical phenomenon of fluorescence has been addressed in isolation, the actual reflection behaviour of real fluorescent surfaces has never been documented, and no analytical BRDF models for such surfaces have been published yet. This paper aims to illustrate the reflection properties typical for diffuse fluorescent surfaces, and provides a BRDF model based on a layered microfacet approach that mimics them.", month = nov, isbn = "1-59593-564-9", location = "Kuala Lumpur, Malaysia", booktitle = "Proceedings of Graphite 2006", pages = "8", pages = "321--328", keywords = "Fluorescence, Analytical BRDF models", URL = "https://www.cg.tuwien.ac.at/research/publications/2006/wilkie-2006-dfs/", }