Comparison Between A* And Obstacle Tracing Pathfinding In Gridless Isometric Game Lailatul Husniah Informatics Department Universitas Muhammadiyah Malang Malang, Indonesia husniah@umm.ac.id Eko Cahyono Informatics Department Universitas Muhammadiyah Malang Malang, Indonesia ekobudi@umm.ac.id Rizky Mahendra Informatics Department Universitas Muhammadiyah Malang Malang, Indonesia rizky.ade.mahendra@gmail.com Ali Sofyan Kholimi Informatics Department Universitas Muhammadiyah Malang Malang, Indonesia kholimi@umm.ac.id Abstract— The pathfinding algorithms have commonly used in video games. City 2.5 is an isometric grid-less game which already implements pathfinding algorithms. However, current pathfinding algorithm unable to produce optimal route when it comes to custom shape or concave collider. This research uses A* and a method to choose the start and end node to produce an optimal route. The virtual grid node is generated to make A* works on the grid-less environment. The test results show that A* be able to produce the shortest route in concave or custom obstacles scenarios, but not on the obstacle-less scenarios and tight gap obstacles scenarios. Keywords—game, pathfinding, A*, grid-less, and isometric I. INTRODUCTION Video games genres and styles have evolved in the past decades. The current technologies make it easier for a developer to implement or combine one genre to another. One of the genres that we studied is 2D simulation games with isometric perspective. In the past time, most the 2D isometric games rely on the grid as its base. Almost every game-objects shown on that game has bounded to that grid. Grid usage also makes it easier to implement pathfinding and mapping. Common A* algorithm could have implemented very well. Unity3D is a game engine to make a high-quality 3D and 2D games [1]. Although it could produce a 2D game, all game objects occupy a 3D space. Thus a default 2D game would not become a grid based game. However, it still possible to develop a grid-based 2D game by generating the grid itself. Based on such occasion, to solve pathfinding problems, we can either generate a virtual 2D grid to implement basic A* pathfinding or create a custom pathfinding method to adapt grid-less environment. “City 2.5” is a grid-less 2D isometric city-building simulation game. Since we are part of the developer who develops this game, we can access and modify every part of this game. City 2.5 use a custom pathfinding method called Obstacle Tracing (OT) [2]. However, this method is not optimal since it cannot always guarantee the shortest path. The tendency of NPC (Non-Player Character) to encircling the obstacle could make the path even longer. NPC is also relying on obstacle collider convex shape which is means when NPC found a concave collider the path taken would be longer. This previous study [3] use Fuzzy Mamdani Logic to solve navigation problems that made better navigation on the robot hexapod fire extinguisher. Other studies [4] use A* to solve pathfinding problems in the 2.5D isometric game. The game is grid-based, which preferable for A* algorithm. The primary goal of that study is to investigate and determine the optimal pathfinding strategy based on several measures such as steps and time have taken to reach the goal using A* algorithm [5]. A* itself is favorable as a pathfinding method as it is simple to implement, is very efficient, and has lots of scope for optimization [6,7]. A* able to generate the shortest path because it uses a heuristic function to estimate the distance of any point to target point [8]. A* implementation on Unity3D has been done by [9], and so we need to adapt the implementation method for this game. A* is an algorithm which measures the heuristic distance between a given point, while the pathfinding itself rely on the search space on how the A* graph represented in the game. In this study [10,11] there are several ways to represent the search space. Previous research [12] use A* to solve pathfinding method for a grid-based graph. In this research, we will use the common A* search space representation, a rectangular grid. The advantage of using the grid is it is easier to generate automatically [13] and easy to implement map representation [14]. Some studies about comparing pathfinding methods have been done by [11,12,13,14,15]. Unfortunately, none of those paper discusses pathfinding on grid-less environment explicitly. What makes this paper different from previous studies is the case study, grid-less environment, and the method Obstacle Tracing, which is rarely used in other paper and research The goal of this paper is to solve NPC pathfinding problems on a grid-less 2D isometric game. Therefore, A* is implemented and compare it with current Obstacle Tracing method. This paper also focuses on how to implement A* properly without altering the unique rules and game design itself. Thus we will limit not to include the computational complexity of the two algorithms, but compare how the path has taken and the speed of computation. Proceeding of EECSI 2018, Malang - Indonesia, 16-18 Oct 2018 978-1-5386-8402-3/18/$31.00 ©2018 IEEE 489