Enemy patrol and chase patterns in Unity - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this patrol position update?

Consider this Unity C# code snippet for enemy patrol between two points. What will be the enemy's position after one update if it starts at (0,0,0) and moves towards (5,0,0) with speed 2 and deltaTime 1?

Unity

Vector3 start = new Vector3(0,0,0);
Vector3 end = new Vector3(5,0,0);
Vector3 position = start;
float speed = 2f;
float deltaTime = 1f;
Vector3 direction = (end - position).normalized;
position += direction * speed * deltaTime;
Debug.Log(position);

A (2.0, 0.0, 0.0)

B (5.0, 0.0, 0.0)

C (1.0, 0.0, 0.0)

D (0.0, 0.0, 0.0)

💡 Hint

Think about how far the enemy moves in one second at speed 2 towards the target.

The enemy moves from (0,0,0) towards (5,0,0) at speed 2 for 1 second, so it moves 2 units along the x-axis, ending at (2,0,0).

🧠 Conceptual

intermediate

Which condition triggers enemy chase in this pattern?

In a typical enemy AI, which condition below best triggers the enemy to stop patrolling and start chasing the player?

A Player is within a certain detection radius of the enemy.

B Enemy health is below 50%.

C Enemy has completed a full patrol cycle.

D Player is outside the game map boundaries.

💡 Hint

Think about what makes the enemy notice the player.

Enemies usually start chasing when the player comes close enough, inside a detection radius.

❓ Predict Output

advanced

What is the enemy's final position after this chase update?

Given this code snippet where enemy chases player at speed 3 for 2 seconds, starting at (1,0,1) and player at (7,0,1), what is the enemy's position after update?

Unity

Vector3 enemyPos = new Vector3(1,0,1);
Vector3 playerPos = new Vector3(7,0,1);
float speed = 3f;
float deltaTime = 2f;
Vector3 direction = (playerPos - enemyPos).normalized;
enemyPos += direction * speed * deltaTime;
Debug.Log(enemyPos);

A (1.0, 0.0, 1.0)

B (7.0, 0.0, 7.0)

C (7.0, 0.0, 1.0)

D (7.0, 0.0, 4.0)

💡 Hint

Calculate the distance moved and check if enemy overshoots the player.

Enemy moves 3*2=6 units towards player from (1,0,1). Distance to player is 6 units, so enemy reaches exactly (7,0,1).

🔧 Debug

advanced

What error does this patrol code cause?

This Unity C# code snippet tries to move enemy between two points but causes an error. What error is it?

Unity

Vector3[] points = {new Vector3(0,0,0), new Vector3(5,0,0)};
int index = 1;
Vector3 position = points[index];
float speed = 2f;
float deltaTime = 1f;
Vector3 direction = (points[index + 1] - position).normalized;
position += direction * speed * deltaTime;
index++;
if(index >= points.Length) index = 0;

A DivideByZeroException

B IndexOutOfRangeException

C No error, runs fine

D NullReferenceException

💡 Hint

Check what happens when index reaches the last element.

When index is at last element, index + 1 accesses out of array bounds causing IndexOutOfRangeException.

🚀 Application

expert

How many patrol points are visited in this loop?

An enemy patrols through points: (0,0,0), (3,0,0), (3,0,3), (0,0,3) in order, moving 1 unit per second. After 10 seconds starting at (0,0,0), how many unique patrol points has the enemy reached or passed?

Unity

Vector3[] patrolPoints = {
  new Vector3(0,0,0),
  new Vector3(3,0,0),
  new Vector3(3,0,3),
  new Vector3(0,0,3)
};
float speed = 1f;
float totalTime = 10f;
int currentIndex = 0;
Vector3 position = patrolPoints[0];
float distanceToNext;
float timeLeft = totalTime;
while(timeLeft > 0) {
  Vector3 nextPoint = patrolPoints[(currentIndex + 1) % patrolPoints.Length];
  distanceToNext = Vector3.Distance(position, nextPoint);
  if(distanceToNext <= speed * timeLeft) {
    timeLeft -= distanceToNext / speed;
    position = nextPoint;
    currentIndex = (currentIndex + 1) % patrolPoints.Length;
  } else {
    position += (nextPoint - position).normalized * speed * timeLeft;
    timeLeft = 0;
  }
}
Debug.Log(currentIndex);

A 4

B 1

C 2

D 3

💡 Hint

Calculate distances between points and how many can be reached in 10 seconds.

Enemy moves along square edges of length 3 units each. Total perimeter is 12 units. In 10 seconds at speed 1, enemy covers 10 units, passing 3 points (0->3->3->0).