Challenge 4: Collision log

Write a C# script that reports collisions with OnCollisionEnter.

Challenge 4: Collision report

In the physics engine, when two solid Colliders make contact, the OnCollisionEnter callback fires. This method delivers colliding object name, contact points, and velocity data via the Collision parameter.

void OnCollisionEnter(Collision collision) {
    Debug.Log("Collided with: " + collision.gameObject.name);
}

Enemy impacts, bullet strikes, or wall collisions trigger their respective gameplay feedback routines inside this function.

Exercise Print collided obstacle

Assign "Obstacle" to the obstacle variable and print Collision: Obstacle to the console.

Show example solution

using System;

class Program
{
    static void Main()
    {
        string obstacle = "Obstacle";
        Console.WriteLine("Collision: " + obstacle);
    }
}

Exercise Print target and obstacle type

Assign "Spike" to target and "Hazard" to type. Print Hit: Spike | Type: Hazard to the console.

Show example solution

using System;

class Program
{
    static void Main()
    {
        string target = "Spike";
        string type = "Hazard";
        Console.WriteLine("Hit: " + target + " | Type: " + type);
    }
}

Test yourself

What type of information is contained inside the Collision parameter passed by Unity into OnCollisionEnter?
- The collided object, contact points, and impact velocity
- Only the instantaneous temperature and memory of the GPU
- The aggregate playback duration of all project audio files
- Only the current frames-per-second (FPS) count of the game
Show answer

The collided object, contact points, and impact velocity — The Collision object encapsulates comprehensive physics data including hit GameObject, surfaces, and impact velocities.

Specify collision parameter type

void OnCollisionEnter(____ collision)

Show answer

void OnCollisionEnter(Collision collision)

Collision report elements

OnCollisionEnter

Physics method on first object contact
Collision

Holds contact & colliding object data
gameObject.name

Name shown in Hierarchy panel
Debug.Log

Logs collision notification to console

Next lesson: Challenge 5: Final synthesis

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