Adding Stealth Mechanics in Unity

Stealth mechanics are gameplay systems that allow players to avoid detection by enemies. Commonly used in stealth-based games like *Assassin’s Creed* or *Hitman*, these mechanics include features such as vision cones, sound detection, hiding spots, and player visibility levels. Adding stealth mechanics can make gameplay more engaging by encouraging strategic thinking and rewarding careful planning.

In this tutorial, we’ll create basic stealth mechanics in Unity. The player will avoid detection by enemies who have vision cones. If the player enters the cone, they’ll be detected.

Step 1: Setting Up the Scene

Start by creating a simple Unity scene:

1. Create a new Unity project.
2. Add a Plane to serve as the ground.
3. Add a 3D model (e.g., a Capsule) to represent the Player.
4. Add another 3D model (e.g., a Cube) to represent an Enemy.
5. Position the Player and Enemy at different locations on the Plane.

Step 2: Creating the Enemy Vision Cone

We’ll simulate the enemy’s vision using a cone-shaped trigger area:

1. Right-click in the Hierarchy and select Create > 3D Object > Cylinder.
2. Resize the cylinder to look like a cone by adjusting its scale (e.g., X = 1, Y = 0.5, Z = 1).
3. Rotate it so the flat base faces forward (e.g., Rotation X = 90).
4. Attach it as a child of the Enemy GameObject.
5. Set the cone’s Collider to be a Trigger.
6. Adjust the scale and position to match the enemy's field of view.

Step 3: Writing the Enemy Detection Script

Now, let’s create a script for detecting the Player within the vision cone:

1. Create a C# script called EnemyVision.
2. Attach the script to the Enemy GameObject.
3. Use the following code:

using UnityEngine;

public class EnemyVision : MonoBehaviour
{
    public bool playerDetected = false;

    void OnTriggerEnter(Collider other)
    {
        if (other.CompareTag("Player"))
        {
            playerDetected = true;
            Debug.Log("Player Detected!");
        }
    }

    void OnTriggerExit(Collider other)
    {
        if (other.CompareTag("Player"))
        {
            playerDetected = false;
            Debug.Log("Player Lost!");
        }
    }
}

This script checks if the Player enters or exits the vision cone. Ensure the Player GameObject has the tag Player.

Step 4: Adding Player Visibility

Next, let’s implement a visibility mechanic to make detection more dynamic. The player will be harder to detect when crouching or hiding:

1. Create a new script called PlayerVisibility.
2. Attach it to the Player GameObject.
3. Use the following code:

using UnityEngine;

public class PlayerVisibility : MonoBehaviour
{
    public float visibility = 1.0f; // Full visibility

    void Update()
    {
        // Reduce visibility when crouching (e.g., pressing "C")
        if (Input.GetKey(KeyCode.C))
        {
            visibility = 0.5f;
            Debug.Log("Crouching: Reduced visibility!");
        }
        else
        {
            visibility = 1.0f; // Default visibility
        }
    }
}

This script adjusts the Player’s visibility level based on their actions. Enemies can later use this value to decide how easily the Player is detected.

Step 5: Enhancing Enemy Detection

Now, let’s combine visibility with detection. Modify the EnemyVision script as follows:

using UnityEngine;

public class EnemyVision : MonoBehaviour
{
    public bool playerDetected = false;

    void OnTriggerStay(Collider other)
    {
        if (other.CompareTag("Player"))
        {
            PlayerVisibility playerVisibility = other.GetComponent<PlayerVisibility>();

            if (playerVisibility != null && playerVisibility.visibility > 0.75f)
            {
                playerDetected = true;
                Debug.Log("Player Detected with high visibility!");
            }
            else
            {
                Debug.Log("Player not visible enough to detect.");
            }
        }
    }

    void OnTriggerExit(Collider other)
    {
        if (other.CompareTag("Player"))
        {
            playerDetected = false;
            Debug.Log("Player Lost!");
        }
    }
}

This script uses the Player’s visibility level to determine whether they are detected.

Step 6: Testing the Stealth Mechanics

To test your setup:

1. Press the Play button in the Unity Editor.
2. Move the Player into the Enemy’s vision cone to trigger detection.
3. Press the crouch button (e.g., "C") to reduce visibility and test how it affects detection.

Optional Enhancements

Here are some ideas to expand your stealth mechanics:

• Sound Detection: Add a mechanic where the enemy detects the Player based on the noise they make (e.g., running).
• Hiding Spots: Create hiding spots where the Player becomes undetectable.
• Patrolling Enemies: Program enemies to patrol along a set path using Unity’s NavMesh system.
• Alert States: Add alert levels for enemies (e.g., suspicious, searching, aggressive).

Conclusion

We've implemented basic stealth mechanics in Unity, including vision cones and visibility levels. These systems can serve as the foundation for more complex stealth gameplay. Experiment with additional features to create a fully immersive stealth experience for your game.