Obstacle avoidance in Unity - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this obstacle detection code?

Consider the following Unity C# script snippet that uses a Raycast to detect obstacles in front of a moving object. What will be printed to the console if there is an obstacle 3 units ahead?

Unity

void Update() {
    if (Physics.Raycast(transform.position, transform.forward, out RaycastHit hit, 5f)) {
        Debug.Log($"Obstacle detected at distance: {hit.distance}");
    } else {
        Debug.Log("No obstacle detected");
    }
}

A NullReferenceException at runtime

B No obstacle detected

C Obstacle detected at distance: 5

D Obstacle detected at distance: 3

💡 Hint

The Raycast checks for obstacles up to 5 units ahead and returns the closest hit distance.

The Raycast detects the obstacle at 3 units ahead, which is within the 5 unit range, so it prints the exact distance.

🧠 Conceptual

intermediate

Which method best describes obstacle avoidance behavior in Unity?

In Unity, which approach is commonly used to make a character avoid obstacles while moving forward?

A Using Raycasts to detect obstacles and steering away from them

B Ignoring obstacles and moving through them

C Using OnCollisionEnter to stop movement permanently

D Using Update() to teleport the character randomly

💡 Hint

Think about how to detect obstacles before hitting them and change direction.

Raycasts allow the character to sense obstacles ahead and adjust movement to avoid collisions.

🔧 Debug

advanced

Why does this obstacle avoidance script fail to detect obstacles?

This Unity script is intended to detect obstacles and stop the character, but it never detects anything. What is the cause?

Unity

void Update() {
    if (Physics.Raycast(transform.position, Vector3.up, out RaycastHit hit, 5f)) {
        Debug.Log("Obstacle detected");
    }
}

A The Raycast direction is upwards, so it misses obstacles in front

B The Raycast distance is too short to detect obstacles

C Physics.Raycast requires a collider on the player object

D The RaycastHit variable is not declared correctly

💡 Hint

Check the direction vector used in the Raycast.

The Raycast is cast upwards (Vector3.up) instead of forward, so it does not detect obstacles in front.

📝 Syntax

advanced

Identify the syntax error in this obstacle avoidance code snippet

Which option contains the correct syntax to perform a Raycast and check if it hits an obstacle within 10 units?

Unity

if (Physics.Raycast(transform.position, transform.forward, out RaycastHit hit, 10f)) {
    Debug.Log("Hit detected");
}

A if (Physics.Raycast(transform.position, transform.forward, out RaycastHit hit)) { Debug.Log("Hit detected"); }

B if (Physics.Raycast(transform.position, transform.forward, out RaycastHit hit, 10f)) { Debug.Log("Hit detected"); }

C if (Physics.Raycast(transform.position, transform.forward, out hit, 10f)) { Debug.Log("Hit detected"); }

D if (Physics.Raycast(transform.position, transform.forward, RaycastHit hit, 10f)) { Debug.Log("Hit detected"); }

💡 Hint

The 'out' keyword must be used with variable declaration inside the method call.

Option B correctly declares 'out RaycastHit hit' inside the Raycast call. Option B misses max distance parameter, Option B misses 'out', Option B misses type declaration.

🚀 Application

expert

What is the final position of the character after this obstacle avoidance logic runs?

A character starts at position (0,0,0) facing forward (z+). It moves forward 5 units unless an obstacle is detected within 3 units. If an obstacle is detected, it turns right 90 degrees and moves forward 2 units. There is an obstacle at (0,0,2). What is the character's final position after running this logic once?

A (0, 0, 2)

B (0, 0, 5)

C (2, 0, 0)

D (0, 0, 0)

💡 Hint

The obstacle is closer than 3 units ahead, so the character turns right and moves 2 units on x axis.

The character detects the obstacle at 2 units ahead, so it turns right (x+ direction) and moves 2 units, ending at (2,0,0).