Mixed-Initiative Tile-Based Designer : Examining Expressive Range And Controllability For 2D Tile-Based Levels

Sammanfattning: This paper investigates the effectiveness of expressive range and controllability for 2-dimensional tile-based procedural content generation. Procedural content generation (PCG) is the automation of content, often in games, and tile-based PCG is when the generated content is constrained to a grid structure. Mixed-initiative PCG, which is the integration of user control into PCG, has been researched previously for tile-based PCG but the implementations have been limited by lack of breadth and user control over the algorithm. As a result, the expressive ranges and controllabilities of their algorithm have not been comprehensive, and in turn, the concepts of expressive range and controllability not thoroughly scrutinized. For the purpose of examining the concepts of expressive range and controllability, an implementation of declarative modelling, named Mixed-initiative Tile-based Designer (MTD), is made. The MTD combines the mission and shape grammar algorithm proposed by Dormans’ and the level generation system in Spelunky. Nine sets of input parameters, scenarios, are tested, each with 2000 levels generated. For each scenario, the expressive range of its output is examined using the standard evaluation metrics linearity and leniency. The results of the data sampling indicated that an analysis based on expressive range needs to be supported by additional analyses for the insights drawn to be more general. In particular, expressive range needs to be complemented by manual inspection, and linearity when applied to sufficiently complex levels needs to be complemented by additional evaluation metrics. On the other hand, controllability was found to have more significant limitations in its current form because of the normalization of the data that goes into the expressive range. One solution is instead to visualize the raw data of the expressive range and make liberal use of manual inspection. As a secondary study, the feasibility of implementing declarative modelling into 2-dimensional tile-based PCG is investigated through analyzing the MTD. In particular, the MTD’s user interface, procedural output and controllability is examined to determine whether declarative modelling is feasible for 2-dimensional tile-based PCG.