SIGGRAPH ASIA 2011 Tutorial

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SIGGRAPH ASIA 2011 Tutorial

Thinking in Layers - Modelling with Layered Surfaces

Andrea Weidlich Alexander Wilkie

September 4, 2011

Abstract

This course serves as a guide on the considerable potential of layered surface models that are available

in many commercial products.The key advantage of using such layered materials over traditional,

more general shading language cons***cts is that the end result is automatically highly physically

plausible because they simulate real materials more precisely. However, this does not mean that these

models cannot be used for artistic purposes.

In particular, we demonstrate on simple layered surface models 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 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 general and the constraints of modelling object appearance

in a physically plausible fashion by explaining basic material properties. We then demonstrate the

techniques that can be used to analyse such materials, both for high quality offline rendering as well

as in a real-time setting before we give examples of the surface types that can be described in this way

and demonstrate how we create them in our company.

Course Overview

1 minute: Welcome and Introduction

Andrea Weidlich and Alexander Wilkie

Overview of the course, and motivation for attending it.

24 minutes: Layered Surfaces in Computer Graphics

Alexander Wilkie

This part of the tutorial outlines the main differences to traditional, shader-language based techniques

to describe object appearance. State-of-the-art layered surface models in commercial products will be

compared. We will also put layered materials in a broader, comparative context with analytic methods

or measured BRDFs of more complex materials and discuss when is it appropriate to use them.

25 minutes: Classifying Materials - Using Layered BRDFs to Describe Object Appearance

Alexander Wilkie

In this part of the tutorial we will classify the appearance of different materials into several groups

according to their reflectance properties. This is necessary since we later use this groups as a guideline

for modelling. This is the technical part of the course since we also discuss physical properties of

materials and how they can be transformed into the world of layered materials.

45 minutes: Modelling with Layered Surfaces

Andrea Weidlich

This part of the course showcases the power of layered materials in a practical setting. For some types

of surface where BRDF measurements are available, we also discuss the performance of the layered

model relative to these measurements, and also compared to other, simpler combined BRDFs. For

each type, we discuss the applications, and the limits of the layered approach.

About the Lecturers

AndreaWeidlich

RTT AG Munich, Germany

andrea.weidlich@rtt.ag

Andrea Weidlich is currently a technical artist at RTT AG in Munich in Germany, as well as being

an external lecturer at Vienna University of Technology in Austria. Prior to this, she was an assistant

professor at Vienna University of Technology, from where she graduated in 2005 with a M.Sc., and

from where she received her PhD in 2009. She also graduated with a M.A. in applied media design

from the University for Applied Arts Vienna (2011). Her current research interests include predictive

rendering with a special focus on appearance modellings.

AlexanderWilkie

Charles University in Prague, Czech Republic

alexander@wilkie.at

AlexanderWilkie is currently a senior lecturer at Charles University in Prague. He achieved his habilitation

in Applied Computer Science from Vienna University of Technology in June 2008, and spent

the time from 2000 to 2008 as an assistant professor at that university. He obtained both his master’s

degree (1996) and Ph.D. (2001) in computer science there. His main research interests are predictive

rendering, colour science, and appearance modelling. He has authored numerous peer-reviewed

papers about computer graphics, and has extensive teaching experience in the areas of photorealistic

rendering and colour science, which he obtained both at Vienna University of Technology, and now at Charles University.

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