Probably the most useful game AI is pathfinding. Pathfinding is all about making your way from one point to another while navigating around obstacles. Unity excels at linking the worlds of designers and programmers. AI is no different, and we'll see how to make simple pathfinding AIs without ever touching the code. Pathfinding is probably the most common AI game task, and there are many Unity plugins for it. We will be looking at three different ones.
In this chapter, you will learn:
- Working with pathfinding
- Applying pathfinding in Quick Path, React, and RAIN AI packages
- Behavior trees
- Applying characters to Character Controller
- Unity's NavMesh
Pathfinding is a way to get an object from point A to point B. Assuming that there are no obstacles, the object can just be moved in the direction of the target. But the AI part of it is all about navigating the obstacles.
A poor AI might try walking a Non-Player Character (NPC) directly to the target. Then, if it is blocked, it randomly tries to go to the right or left to look for a space that might help. The character can get caught in different areas and become permanently stuck.
A better AI will walk an NPC in an intelligent way to a target, and will never get stuck in different areas. To compute a good path for the NPC to walk, the AI system will use a graph that represents the game level, and a graph search algorithm is used to find the path. The industry-standard algorithm for pathfinding is A* (A Star), a quick graph search algorithm that uses a cost function between nodes—in pathfinding usually the distance—and the algorithm tries to minimize the overall cost (distance) of the path. If you want to learn to code your own pathfinding AI, try A* because it is simple to implement and has a lot of simple improvements that you can apply for your game's needs.
The AIs we are about to discuss will take care of the pathfinding algorithms for you, and ultimately reduce the time it takes to breathe AI life into your game. Now let's look at Quick Path AI.