Pathfinding basics in Unity - Mini Project: Build & Apply

Pathfinding basics

📖 Scenario: You are creating a simple game where a character moves from one point to another on a grid. You want to teach how to find a path step-by-step using basic pathfinding logic.

🎯 Goal: Build a simple pathfinding script that finds a path from a start position to an end position on a grid using a basic algorithm.

📋 What You'll Learn

Create a grid represented by a 2D array

Set start and end positions

Implement a simple pathfinding logic to find a path

Print the path coordinates

💡 Why This Matters

🌍 Real World

Pathfinding is used in games and robotics to move characters or robots from one place to another avoiding obstacles.

💼 Career

Understanding basic pathfinding helps in game development, AI programming, and simulation tasks.

1

Create the grid data

Create a 2D integer array called grid with 3 rows and 3 columns. Fill it with zeros.

Unity

// Create a 2D integer array called grid with 3 rows and 3 columns filled with zeros
// Your code here

Hint

Use int[,] grid = new int[3, 3] and fill with zeros inside curly braces.

2

Set start and end positions

Create two variables: start and end of type Vector2Int. Set start to (0, 0) and end to (2, 2).

Unity

int[,] grid = new int[3, 3] {
    {0, 0, 0},
    {0, 0, 0},
    {0, 0, 0}
};
// Create Vector2Int variables start and end with values (0, 0) and (2, 2)
// Your code here

Hint

Use Vector2Int start = new Vector2Int(0, 0); and similarly for end.

3

Find a simple path

Create a List<Vector2Int> called path. Use a for loop to add positions from start to end moving right then down (first increase x, then y).

Unity

int[,] grid = new int[3, 3] {
    {0, 0, 0},
    {0, 0, 0},
    {0, 0, 0}
};

Vector2Int start = new Vector2Int(0, 0);
Vector2Int end = new Vector2Int(2, 2);

// Create a List called path and add positions moving right then down
// Your code here

Hint

Use two loops: one to move right (x changes), one to move down (y changes). Add each position to path.

4

Print the path

Use a foreach loop to print each position in path in the format (x, y).

Unity

using System.Collections.Generic;
using UnityEngine;

int[,] grid = new int[3, 3] {
    {0, 0, 0},
    {0, 0, 0},
    {0, 0, 0}
};

Vector2Int start = new Vector2Int(0, 0);
Vector2Int end = new Vector2Int(2, 2);

List path = new List();

for (int x = start.x; x <= end.x; x++) {
    path.Add(new Vector2Int(x, start.y));
}
for (int y = start.y + 1; y <= end.y; y++) {
    path.Add(new Vector2Int(end.x, y));
}

// Print each position in path as (x, y)
// Your code here

Hint

Use foreach (Vector2Int pos in path) and Debug.Log($"({pos.x}, {pos.y})") to print positions.

Practice

1. What is the main purpose of pathfinding in Unity games?

easy

A. To help game objects move from one point to another avoiding obstacles

B. To create visual effects like explosions

C. To manage game audio settings

D. To design user interface layouts

Solution

1. Step 1: Understand pathfinding concept

   Pathfinding is used to find a route for characters or objects to move smartly in a game world.

2. Step 2: Identify Unity's use of pathfinding

   Unity uses pathfinding to move game objects from one point to another while avoiding obstacles.

3. Final Answer:

   To help game objects move from one point to another avoiding obstacles -> Option A

4. Quick Check:

   Pathfinding = smart movement [OK]

Hint: Pathfinding = smart movement avoiding obstacles [OK]

Common Mistakes:

• Confusing pathfinding with graphics or audio
• Thinking pathfinding manages UI
• Assuming pathfinding creates effects

2. Which of the following is the correct way to set a destination for a NavMeshAgent in Unity?

easy

A. agent.Navigate(target.position);

B. agent.MoveTo(target.position);

C. agent.GoTo(target.position);

D. agent.SetDestination(target.position);

Solution

1. Step 1: Recall NavMeshAgent method for setting destination

   The correct method to set a destination is SetDestination(Vector3 target).

2. Step 2: Match method names with options

   Only agent.SetDestination(target.position); uses SetDestination correctly; others are invalid method names.

3. Final Answer:

   agent.SetDestination(target.position); -> Option D

4. Quick Check:

   SetDestination sets target [OK]

Hint: Remember NavMeshAgent uses SetDestination() method [OK]

Common Mistakes:

• Using non-existent methods like MoveTo or GoTo
• Forgetting to pass target.position as Vector3
• Confusing method names with other APIs

3. What will be the output of this Unity C# code snippet?

using UnityEngine;
using UnityEngine.AI;

public class MoveAgent : MonoBehaviour {
    public Transform target;
    private NavMeshAgent agent;

    void Start() {
        agent = GetComponent<NavMeshAgent>();
        agent.SetDestination(target.position);
    }

    void Update() {
        if (agent.remainingDistance < 0.5f) {
            Debug.Log("Reached target");
        }
    }
}

medium

A. Logs "Reached target" immediately on start

B. Logs "Reached target" when agent is close to target

C. Throws a runtime error because NavMeshAgent is missing

D. Never logs anything

Solution

1. Step 1: Understand NavMeshAgent behavior in Start()

   The agent sets its destination to the target's position at start.

2. Step 2: Check Update() condition for logging

   When the agent is within 0.5 units of the target, it logs "Reached target".

3. Final Answer:

   Logs "Reached target" when agent is close to target -> Option B

4. Quick Check:

   Agent logs on close arrival [OK]

Hint: remainingDistance < 0.5 triggers log near target [OK]

Common Mistakes:

• Assuming log happens immediately
• Ignoring NavMeshAgent setup requirement
• Thinking it throws error without NavMeshAgent component

4. Identify the error in this Unity C# code for pathfinding:

public class AgentMover : MonoBehaviour {
    public Transform target;
    private NavMeshAgent agent;

    void Start() {
        agent = GetComponent<NavMeshAgent>();
        agent.SetDestination(target);
    }
}

medium

A. SetDestination requires a Vector3, not a Transform

B. NavMeshAgent component is not assigned

C. Missing Update method to move agent

D. target variable should be private

Solution

1. Step 1: Check SetDestination parameter type

   SetDestination expects a Vector3 position, but target is a Transform object.

2. Step 2: Correct usage of SetDestination

   Use target.position to pass Vector3 instead of target directly.

3. Final Answer:

   SetDestination requires a Vector3, not a Transform -> Option A

4. Quick Check:

   SetDestination needs Vector3 [OK]

Hint: Use target.position, not target, in SetDestination [OK]

Common Mistakes:

• Passing Transform instead of Vector3
• Assuming NavMeshAgent auto-assigns
• Thinking Update method is mandatory for movement

5. You want a NavMeshAgent to move to a target only if the path is valid and reachable. Which code snippet correctly checks this before moving?

hard

A. if (agent.CalculatePath(target.position, new NavMeshPath()) && agent.SetDestination(target.position)) { /* move */ }

B. agent.SetDestination(target.position); if (agent.pathStatus == NavMeshPathStatus.PathComplete) { /* move */ }

C. NavMeshPath path = new NavMeshPath(); if (agent.CalculatePath(target.position, path) && path.status == NavMeshPathStatus.PathComplete) { agent.SetDestination(target.position); }

D. if (agent.isOnNavMesh) { agent.SetDestination(target.position); }

Solution

1. Step 1: Understand path validation with CalculatePath

   CalculatePath fills a NavMeshPath object and returns true if path calculation succeeded.

2. Step 2: Check path status for completeness

   Only if path.status is PathComplete is the path valid and reachable.

3. Step 3: Set destination only if path is valid

   NavMeshPath path = new NavMeshPath(); if (agent.CalculatePath(target.position, path) && path.status == NavMeshPathStatus.PathComplete) { agent.SetDestination(target.position); } correctly creates a path, checks status, then sets destination.

4. Final Answer:

   NavMeshPath path = new NavMeshPath(); if (agent.CalculatePath(target.position, path) && path.status == NavMeshPathStatus.PathComplete) { agent.SetDestination(target.position); } -> Option C

5. Quick Check:

   CalculatePath + PathComplete check = safe move [OK]

Hint: Use CalculatePath and check PathComplete before SetDestination [OK]

Common Mistakes:

• Ignoring path status after CalculatePath
• Calling SetDestination without path check
• Using wrong method signatures