Computer Science
Grade 7
20 min
Artificial Intelligence for Games: Pathfinding and Behavior Trees
Explore AI techniques for games, including pathfinding (A*, Dijkstra's) and behavior trees, and how to implement them to control the behavior of game characters.
Tutorial Preview
1
Introduction & Learning Objectives
Learning Objectives
Define pathfinding and its role in making game characters move intelligently.
Explain what a Behavior Tree is and how it helps characters make decisions.
Differentiate between a Sequence node and a Selector node in a Behavior Tree.
Trace the logic of a simple Behavior Tree to predict a character's actions.
Design a simple Behavior Tree for a common game scenario, like a guard's patrol.
Map out a basic path for a character on a grid, avoiding obstacles.
Ever wonder how a video game enemy knows exactly how to chase you around a wall instead of running into it? 🤖 Let's find out!
In this lesson, we'll explore two advanced Artificial Intelligence (AI) topics that make game characters seem smart. We'll learn how they find their way ar...
2
Key Concepts & Vocabulary
TermDefinitionExample
PathfindingThe process of finding the shortest or best route between two points, while avoiding obstacles.A knight in a castle game finding the quickest way from the barracks to the treasure room without walking through walls.
Behavior TreeA smart flowchart that helps a game character decide what action to take. It's read from left to right, top to bottom.A zombie's Behavior Tree might decide: 'Is a player nearby? If yes, chase them. If no, wander around.'
NodeA single step or decision point in a Behavior Tree. It can be a question, a task, or a way to organize other nodes.In a guard's Behavior Tree, 'See Player?', 'Chase Player', and 'Patrol Route' are all nodes.
Selector NodeA type of node in a Behavior Tree th...
3
Core Syntax & Patterns
The Selector (?) Pattern
Selector Node -> [Action 1, Action 2, Action 3]
Use this when a character has to choose ONE action from a list of possibilities. It tries Action 1. If it succeeds, it stops. If it fails, it tries Action 2, and so on. It's for making choices.
The Sequence (→) Pattern
Sequence Node -> [Action 1, Action 2, Action 3]
Use this when a character must perform a series of actions in a specific order. It tries Action 1. If it succeeds, it tries Action 2. If any action in the list fails, the entire sequence stops and fails. It's for following a plan.
4 more steps in this tutorial
Sign up free to access the complete tutorial with worked examples and practice.
Sign Up Free to ContinueSample Practice Questions
Challenging
You are designing a shy creature. Its behaviors are: 1) If it sees a player, it must run to a hiding spot. 2) If it's hungry, it must find food. 3) Otherwise, it will wander. What is the best root node and the order of checks for its Behavior Tree?
A.Sequence -> [Hide, Find Food, Wander]
B.Selector -> [Wander, Find Food, Hide]
C.Sequence -> [Wander, Find Food, Hide]
D.Selector -> [Hide, Find Food, Wander]
Challenging
A character has this tree: `Selector -> [Is Enemy Close?, Sequence -> [Is Health Low?, Flee]]`. If the enemy is FAR away and the character's health is LOW, what is the final outcome?
A.The character flees.
B.The Selector fails, and the character does nothing from this tree.
C.The Sequence runs, but fails, so the character does nothing.
D.The character checks its health, then stands still.
Challenging
Consider the pathfinding grid from Example 1. The path D-D-D-R-R-R has a length of 6. Is this the ONLY shortest path?
A.Yes, it is the only possible path to the battery.
B.No, there is a shorter path with a length of 5.
C.No, the path R-R-R-D-D-D is also a shortest path with length 6.
D.Yes, because moving Right first is always slower.
Want to practice and check your answers?
Sign up to access all questions with instant feedback, explanations, and progress tracking.
Start Practicing Free