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The Manuka rendering architecture has been designed in the spirit of the classic reyes rendering architecture: to enable the creation of visually rich computer generated imagery for visual effects in movie production. Following in the footsteps of reyes over the past 30 years, this means supporting extremely complex geometry, texturing, and shading. In the current generation of renderers, it is essential to support very accurate global illumination as a means to naturally tie together different assets in a picture. This is commonly achieved with Monte Carlo path tracing, using a paradigm often called shade on hit , in which the renderer alternates tracing rays with running shaders on the various ray hits. The shaders take the role of generating the inputs of the local material structure, which is then used by path-sampling logic to evaluate contributions and to inform what further rays to cast through the scene. We propose a shade before hit paradigm instead and minimise I/O strain on the system, leveraging locality of reference by running pattern generation shaders before we execute light transport simulation by path sampling. We describe a full architecture built around this approach, featuring spectral light transport and a flexible implementation of multiple importance sampling ( mis ), resulting in a system able to support a comparable amount of extensibility to what made the reyes rendering architecture successful over many decades.

We present a spectral rendering technique that offers a compelling set of advantages over existing approaches. The key idea is to propagate energy along paths for a small, constant number of changing wavelengths. The first of these, the hero wavelength, is randomly sampled for each path, and all directional sampling is solely based on it. The additional wavelengths are placed at equal distances from the hero wavelength, so that all path wavelengths together always evenly cover the visible range.

The emissive properties of glowing solid objects appear to be something that the graphics community has not considered in depth before. While the volumetric emission of plasma, i.e. flames, has been discussed numerous times, and while the emission characteristics of entire luminaires can be handled via IESNA profiles, the exact appearance of glowing solid objects appears to have eluded detailed scrutiny so far. In this paper, we discuss the theoretical background to thermally induced light emission of objects, describe how one can handle this behaviour with very little effort in a physically based rendering system, and provide examples for the visual importance of handling this in a plausible fashion.

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.

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.

In this article we derive the complete set of formulas 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 polarization-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 polarization effects. The formulas we derive can be directly used in a ray based renderer, and we demonstrate these capabilities in test scenes.

In Computer Graphics, the polarisation properties of light currently play a role in several contexts: in certain forms of highly realistic ray-based image synthesis (sometimes colloquially referred to as Polarisation Ray Tracing), in some 3D display systems, and in some material acquisition technologies. The properties of light that are behind all of these applications are basically the same, although the technologies for which this property of light is being used differ considerably. Also, the notations and mathematical formalisms used in these application areas differ to some degree as well. This course aims to provide a unified resource for those areas of computer graphics which require a working knowledge of light polarisation: rendering and material acquisition. Consequently, the course is structured into three main parts: I - Background, II - Polarisation Ray Tracing, and III - Polarised Light in Acquisition Technology. Care is taken so that the information provided in Part I is applicable to both Part II and III of the course, and is formulated in a way that emphasises the underlying similarities.

This course serves as a guide to the considerable potential of layered surface models that are available in many commercial products. The key advantage of using such layered materials over traditional shading language constructs is that the end result is highly physically plausible because it simulates real materials more precisely. However, this does not mean that these models cannot be used for artistic purposes. Using simple layered surface models, we demonstrate how a surprisingly large number of interesting and important surface types can be efficiently represented. We also show how handy such an approach is for the 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 general and the constraints of modeling object appearance in a physically plausible fashion by explaining basic material properties. We then demonstrate the techniques that are used to analyze such materials, both for high quality offline rendering as well as in a realtime setting. We then give examples of the surface types that can be described in this way and demonstrate how we create them in our company.

Polarisation Ray Tracing is a bit like spectral rendering. You might have heard about it, but the technical details - what exactly it is all about, how it is best done, what the benefits are, where you ought to use it, and where you can safely omit it - are not that well known. At least in principle, information about all this is available already - but it is scattered across many different sources, some of which are outside graphics literature, and consequently can be a bit hard to find at first. Also, a number of these resources - in particular publications in physics literature - were not written with graphics engineering in mind, and can prove hard to directly apply to the engineering problem of getting such a Tenderer to work. This course aims to provide a unified one-stop information resource on this topic, and should enable graphics engineers with a background in physically-based rendering to properly assess whether the phenomenon has to be included in a given simulation, and what has to be done in order to properly allow for handling of the phenomenon in a ray-based Tenderer. However, the contents of the course are also potentially very relevant for other areas of graphics beyond rendering proper: polarised light is currently being used in several other contexts, such as face scanning, highlight removal, or 3D projection technologies. Engineers and researchers in these other areas might benefit from the course insofar as the knowledge needed for an outright simulation of polarised light transport presented here is a superset of the information needed for more specialised tasks. This comprehensive overview would thus be a useful repository of knowledge for other areas as well.

We discuss issues surrounding the visualisation of the polarisation properties of light stored in the pixels of an image. In order to facilitate comparisons between the work of different researchers, and in order to aid the development and debugging of polarisation-capable rendering systems, we propose a set of four standardised, easily comprehensible visualisations. These cover all aspects of polarisation that are relevant for rendering research, but also for optical design tasks. However, the so-called luminance scaled overlay form of the proposed visualisations is conceivably also useful and instructive to a wider, non-technical audience, and can be used for educational purposes.

This course intends to serve two closely related purposes: to provide an accurate definition of the term "predictive rendering" and to present the technological foundations for research in this area. The first goal of the course (a clear definition of the term) seems to be necessary due to the extreme prevalence of its antonym: believable rendering. Practically all contemporary production graphics, as well as most current graphics research efforts, fall into the latter category. The second (much larger and technical) part of the course presents the foundations of current predictive rendering. Unlike believable rendering, where any technology that delivers visually convincing results is acceptable for a given task, a predictive pipeline has the fundamental problem that all components have to be of a uniformly high quality to ensure a reliable result. The course describes an entire predictive pipeline, and for each stage it presents the graphics technologies (in some cases surprisingly few) that can be used in such a context. This course should enable anyone with a background in graphics to bootstrap a basic predictive rendering environment that can support further research.

The key advantage of using layered BRDFs over traditional, more general shading-language constructs is that the automatic result is highly plausible. This course is a survey of the considerable potential of layered surface models. On a simple layered surface model that combines several traditional BRDF components, it demonstrates how a surprisingly large number of interesting and important surface types can be efficiently represented by using the same, not particularly complex, BRDF code. It also shows how handy such an approach is for the eventual end user, whose main concern is the ease of describing object appearance based only on a few intuitive parameters. The course begins with a discussion of layered surface models in computer graphics and the constraints of modelling object appearance in a physically plausible fashion, then demonstrates the techniques that can be used to efficiently evaluate layered BRDF models and presents examples of the surface types that can be described in this way. The course goes beyond plain-surface models to 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.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.

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.

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.

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.