Incorporating required structure into tiles

Search based procedural content generation uses search techniques to locate high-quality content elements for use in games. This study extends an evolutionary-computation based system to generate tiles used to assemble floor plans for levels in a video game as well as evolving assembly plans. The separate evolution of assembly plans and tiles yields a decomposition of the level generation problem that saves substantial time. The tiles used in this study use a more sophisticated fitness function than earlier studies and also permit the user to specify features, e.g. rooms of a particular shape or short or long transit distances between two points in the tile. Evolutionary computation is used as an off-line tool to generate libraries of both tiles and assembly plans. Systems for rapidly assembling tile libraries can then be used to generate large levels on demand with combinatorially huge numbers of level plans available. The new fitness function can be used to control the topology of the tiles and optionally permits the incorporation of enforced symmetry in tiles. Symmetric tiles are found to have a visually striking appearance. Control is achieved by requesting that different pairwise distances between user-specified checkpoints be minimized, maximized, or left free. This study explores the new fitness functions and demonstrates the variety of tiles that can be generated as well as assembling exemplary level plans from those tiles.