# Biome Generation Tool: A Mixed-Initiative Software for the Procedural Generation of Biomes
## 1 Introduction  
Creating a videogame or interactive experience is a complex process that requires a balance between creativity, narrative, and technological implementation [1]. In this scenario, the map or level is an essential component in various game genres, regardless of their complexity. This is because maps provide coherence between all other components, so they must be designed to support the mechanics and characteristics of the game while providing the proper space to develop a good game flow. The confection of a map by a designer can take a lot of time and resources [2], even more when considering that a vast number of games have quite a few maps, or the maps used are extensive, or both. Nevertheless, the design and development of game maps are highly time-consuming processes. Therefore, researchers and developers work constantly to simplify these tasks in the development process. One of the reasons procedural content generation (PCG) systems were created was as an attempt to overcome this complication [3]. PCG can reduce production costs [4], but it comes with a trade-off. For PCG to generate a final product, the algorithm must be sophisticated enough or iterate multiple times and select which one to use among the results. In both cases, the designer has decreased control over the generated product, and even if the result is good, it may end up not being used if it does not follow the designer's intentions. Therefore, creativity and control in the design process become unbalanced and may lead level designers to avoid using these kinds of tools. How can we benefit from PCG algorithms without losing control over the outcome? A recent research area in content generation is _mixed-initiative_ tools. Mixed-initiative tools delve into the area of Human-AI interaction to create a system in which an algorithm andthe designer collaborate to create the content, thus reducing the workload and keeping a high degree of control. In this context, we have developed a mixed-initiative tool for the creation of map environments in the Unity3D game engine, called Biome Generation Tool (BGT). A biome is a set of plants and animals that share common characteristics due to jointly inhabiting a particular environment. These organisms usually present multiple interrelationships between themselves and their surroundings. Biomes are important in game map design, particularly in genres such as Real Time Strategy, Adventure, or Survival. This tool is expected to reduce the workload and time invested in the process of making levels while maintaining the degree of control the designer has over the generated content, allowing them to convey their intent. Most of the mixed-initiative procedural content generation tools described in the literature are standalone research platforms (see for example [5; 6; 7; 8; 9]). However, as a differential factor, BGT has been designed to be integrated into a world-class game engine, Unity3D. In this work, the creation process of BGT is described. BGT is a biome generation tool that lets the designer edit and create map environments for pre-existing maps. It allows the user to decide what objects will be part of the environment, define the area on the map where they will be placed and control the number of elements that will be included. BGT is also equipped with an AI based on an Evolutionary Algorithm (EA) [10] that evaluates the current state of the designer's work and provides insight or suggestions for modifications. An EA was selected as the AI for BGT due to its robustness and effectiveness. EAs provide good results over large populations and are less susceptible to noise or changes in input throughout the process [11]. Another advantage is that they do not need pre-existing training data as supervised learning methods do. The designer can control the interference of the AI by enabling or disabling it and choosing whether to apply or ignore the modifications.