Mesh and mesh renderer in Unity - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Unity C# code snippet?

Consider the following code that creates a simple mesh with 3 vertices forming a triangle. What will be the number of vertices in the mesh after running this code?

Unity

Mesh mesh = new Mesh();
Vector3[] vertices = new Vector3[] {
    new Vector3(0, 0, 0),
    new Vector3(1, 0, 0),
    new Vector3(0, 1, 0)
};
int[] triangles = new int[] { 0, 1, 2 };
mesh.vertices = vertices;
mesh.triangles = triangles;
Debug.Log(mesh.vertexCount);

A 3

B 0

C 1

D 6

💡 Hint

Count how many unique points you define in the vertices array.

The mesh has exactly 3 vertices defined in the vertices array. The vertexCount property returns the number of vertices, which is 3.

🧠 Conceptual

intermediate

What does the MeshRenderer component do in Unity?

Choose the correct description of the MeshRenderer component's role in Unity.

A It handles physics collisions for the mesh.

B It defines the shape and vertices of the mesh.

C It renders the mesh on the screen using materials and lighting.

D It stores the texture data for the mesh.

💡 Hint

Think about what makes a mesh visible in the game view.

The MeshRenderer component is responsible for drawing the mesh on the screen. It uses materials and lighting to display the mesh visually. The mesh shape is defined by the Mesh component, not the renderer.

🔧 Debug

advanced

Why does this mesh not appear in the scene?

The following code creates a mesh but nothing appears in the scene. What is the most likely reason?

Unity

Mesh mesh = new Mesh();
mesh.vertices = new Vector3[] {
    new Vector3(0, 0, 0),
    new Vector3(1, 0, 0),
    new Vector3(0, 1, 0)
};
mesh.triangles = new int[] { 0, 1, 2 };

GameObject obj = new GameObject("Triangle");
obj.AddComponent<MeshFilter>().mesh = mesh;
// Missing MeshRenderer component

A The mesh vertices are all at the same position.

B The mesh triangles array is empty.

C The mesh has no vertices defined.

D The GameObject is missing a MeshRenderer component.

💡 Hint

Think about what component is needed to make a mesh visible.

Without a MeshRenderer component, the mesh will not be drawn on the screen even if the mesh data is correct. Adding a MeshRenderer will fix the issue.

📝 Syntax

advanced

Identify the syntax error in this mesh creation code

Which option correctly fixes the syntax error in the following code snippet?

Mesh mesh = new Mesh();
mesh.vertices = new Vector3[] {
    new Vector3(0, 0, 0),
    new Vector3(1, 0, 0),
    new Vector3(0, 1, 0)
};
mesh.triangles = new int[] { 0, 1, 2 } // missing semicolon

A Replace the square brackets [] with parentheses () in the arrays.

B Add a semicolon at the end of the triangles assignment line.

C Remove the commas between the Vector3 elements.

D Change 'new Vector3' to 'Vector3()' without 'new'.

💡 Hint

Check the end of each statement in C#.

In C#, each statement must end with a semicolon. The missing semicolon after the triangles array assignment causes a syntax error.

🚀 Application

expert

What is the output of this code modifying mesh normals?

This code modifies the normals of a mesh. What will be the value of mesh.normals[0] after running?

Unity

Mesh mesh = new Mesh();
mesh.vertices = new Vector3[] {
    new Vector3(0, 0, 0),
    new Vector3(1, 0, 0),
    new Vector3(0, 1, 0)
};
mesh.triangles = new int[] { 0, 1, 2 };
mesh.normals = new Vector3[] {
    new Vector3(0, 0, 1),
    new Vector3(0, 0, 1),
    new Vector3(0, 0, 1)
};
mesh.normals[0] = new Vector3(1, 0, 0);
Debug.Log(mesh.normals[0]);

A (1.0, 0.0, 0.0)

B (0.0, 0.0, 1.0)

C (0.0, 0.0, 0.0)

D NullReferenceException

💡 Hint

Think about how arrays and structs work in C# when modifying elements.

The code sets the first normal vector to (1, 0, 0). Accessing mesh.normals[0] after this change returns the updated vector.