Cameron Browne

A Survey of Monte Carlo Tree Search Methods

Monte Carlo tree search (MCTS) is a recently proposed search method that combines the precision of tree search with the generality of random sampling. It has received considerable interest due to its spectacular success in the difficult problem of computer Go, but has also proved beneficial in a range of other domains. This paper is a survey of the literature to date, intended to provide a snapshot of the state of the art after the first five years of MCTS research. We outline the core algorithms derivation, impart some structure on the many variations and enhancements that have been proposed, and summarize the results from the key game and nongame domains to which MCTS methods have been applied. A number of open research questions indicate that the field is ripe for future work.

Search-Based Procedural Content Generation: A Taxonomy and Survey

The focus of this survey is on research in applying evolutionary and other metaheuristic search algorithms to automatically generating content for games, both digital and nondigital (such as board games). The term search-based procedural content generation is proposed as the name for this emerging field, which at present is growing quickly. A taxonomy for procedural content generation is devised, centering on what kind of content is generated, how the content is represented and how the quality/fitness of the content is evaluated; search-based procedural content generation in particular is situated within this taxonomy. This article also contains a survey of all published papers known to the authors in which game content is generated through search or optimisation, and ends with an overview of important open research problems.

Evolutionary Game Design

It is easy to create new combinatorial games but more difficult to predict those that will interest human players. We examine the concept of game quality, its automated measurement through self-play simulations, and its use in the evolutionary search for new high-quality games. A general game system called Ludi is described and experiments conducted to test its ability to synthesize and evaluate new games. Results demonstrate the validity of the approach through the automated creation of novel, interesting, and publishable games.

Search-based procedural content generation

Recently, a small number of papers have appeared in which the authors implement stochastic search algorithms, such as evolutionary computation, to generate game content, such as levels, rules and weapons. We propose a taxonomy of such approaches, centring on what sort of content is generated, how the content is represented, and how the quality of the content is evaluated. The relation between search-based and other types of procedural content generation is described, as are some of the main research challenges in this new field. The paper ends with some successful examples of this approach.

Duotone Truchet-like tilings

This paper explores methods for colouring Truchet-like tiles, with an emphasis on the resulting visual patterns and designs. The methods are extended to non-square tilings that allow Truchet-like patterns of noticeably different character. Underlying parity issues are briefly discussed and solutions presented for parity problems that arise for tiles with odd numbers of sides. A new tile design called the arch tile is introduced and its artistic use demonstrated.

Evolving 3d buildings for the prototype video game subversion

We investigate user-guided evolution for the development of virtual 3D building structures for the prototype (commercial) game Subversion, which is being developed by Introversion Software Ltd. Buildings are described in a custom plain-text markup language that can be parsed by Subversion’s procedural generation engine, which renders the 3D models on-screen. The building descriptions are amenable to random generation, crossover and mutation, which enabled us to implement and test a user-driven evolutionary approach to building generation. We performed some fundamental experimentation with ten participants to determine how visually similar child buildings are to their parents, when generated in differing ways. We hope to demonstrate the potential of user-guided evolution for content generation in games in general, as such tools require very little training, time or effort to be employed effectively.

Elegance in Game Design

This paper explores notions of elegance and shibui in combinatorial game design, and describes simple computational models for their estimation. Elegance is related to a games simplicity, clarity, and efficiency, while shibui is a more complex concept from Japanese aesthetics that also incorporates depth. These provide new metrics for quantifying and categorizing games that are largely independent of existing measurements such as tractability and quality. Relevant ideas from Western and Eastern aesthetics are introduced, the meaning of elegance and shibui in combinatorial games is examined, and methods for estimating these values empirically are derived from complexity analyses. Elegance and shibui scores are calculated for a number of example games, for comparison. Preliminary results indicate shibui estimates to be more reliable than elegance estimates.

Rules and Mechanics

Rules are at the core of many games. So how about generating them? This chapter discusses various ways to encode and generate game rules, and occasionally game entities that are strongly tied to rules. The first part discusses ways of generating rules for board games, including Ludi, perhaps the most successful example of automatically generated game rules. The second part discusses some more tentative attempts to generate rules for video games, in particular 2D games with graphical logic. Most approaches to generating game rules have used search-based methods such as evolution, but there are also some solver-based approaches.

Deductive search for logic puzzles

Deductive search (DS) is a breadth-first, depth-limited propagation scheme for the constraint-based solution of deduction puzzles, using simple logic operations found in standard constraint satisfaction solvers. It attempts to emulate the processing limits experienced by human solvers, and, to some extent, the process by which they solve such problems. Any solution deduced by DS is guaranteed to be correct and unique. Further, it provides an estimate of the deducibility of a given problem for human solvers and offers new ways of understanding deduction puzzles. Its performance is tested on a number of problem domains including Japanese logic puzzles, a traditional logic puzzle, and a geometric placement puzzle.

Computational creativity in a closed game system

This paper describes the early stages of an experiment investigating the role of the computer as a creative collaborator in the game design process. We introduce the Shibumi set, a closed game system so simple that its rule space can be completely defined, yet deep enough to allow interesting games to emerge. Constraining the search space to such a closed system has computational benefits, but had unexpected effects on the creative process of designers during a related game design contest. These effects yield some insight into the creative process of experienced game designers, in particular, the way they search for rule sets to realise desired behaviours, and suggest a simple unified model of the game design process. We suggest ways in which these insights may be incorporated into future work, to produce software that might not only search for new games more effectively and assist the designer as a creative collaborator, but to automate the game design process in ways that might be perceived as more creative.