Procedural modelling in Houdini based on Function Representation

Chapter 1
Introduction
In the visual effects and games <strong>in</strong>dustry, the predom<strong>in</strong>ant <strong>modell<strong>in</strong>g</strong> techniques are us<strong>in</strong>g
polygonal meshes. While these offer various benefits and are well <strong>in</strong>tegrated <strong>in</strong>to current
pipel<strong>in</strong>es, they only represent surfaces and have a given amount of detail. As a consequence,
<strong>in</strong>formation about an object <strong>in</strong>ternal structure cannot be stored and <strong>modell<strong>in</strong>g</strong> of heterogeneous
real-world objects is difficult. In other fields like CAD and 3D pr<strong>in</strong>t<strong>in</strong>g, the tradeoffs
cannot be circumvented without effort and alternative representations are needed.
One alternative is to use “Function representation <strong>in</strong> geometric <strong>modell<strong>in</strong>g</strong>” as suggested by
Pasko et al. (1995). The so-called FRep allows the def<strong>in</strong>ition of objects, operations and
relations as a mathematical function as opposed to po<strong>in</strong>t data and meshes. A lot of research
<strong>in</strong> this field has been done at the NCCA. The FRep API (Kravtsov 2011) was taken as base
for this project.
This thesis documents the design and implementation of a custom plug<strong>in</strong> for Houd<strong>in</strong>i that
was written <strong>in</strong> C++ us<strong>in</strong>g the Houd<strong>in</strong>i Development Kit (HDK). Houd<strong>in</strong>i is a high-end 3D
animation package developed by Side Effects Software and used heavily <strong>in</strong> the VFX <strong>in</strong>dustry.
Due to its node-<strong>based</strong> architecture, it is very suitable for procedural <strong>modell<strong>in</strong>g</strong>. Moreover,
many of the concepts <strong>in</strong> the FRep API, like for example the tree and node structure, translate
and <strong>in</strong>tegrate very well <strong>in</strong>to the software.
Chapter 2 gives an overview of the topic and related research. In Chapter 3, the relevant
concepts of the APIs used, namely the exist<strong>in</strong>g FRep API and the Houd<strong>in</strong>i Development Kit,
are <strong>in</strong>troduced. Chapter 4 documents the conceptual design of the plug<strong>in</strong> and further details
particular to the development environment and workflow. Furthermore, the <strong>modell<strong>in</strong>g</strong> process
and key algorithms are expla<strong>in</strong>ed. Chapter 5 presents results and gives an idea over potential
applications. The results are evaluated <strong>in</strong> Chapter 6 where future work and improvements
are discussed.
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