Material properties in Unity - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Unity C# code changing material color?

Consider this Unity C# script snippet that changes a material's color in the Start() method. What color will the material have after running?

Unity

using UnityEngine;

public class ColorChanger : MonoBehaviour {
    void Start() {
        Renderer rend = GetComponent<Renderer>();
        rend.material.color = Color.red;
        rend.material.color = new Color(0, 1, 0, 1); // green
    }
}

A The material color will be green.

B The material color will be red.

C The material color will be blue.

D The material color will be white.

💡 Hint

Think about the order of color assignments.

The material color is first set to red, then immediately changed to green. The last assignment determines the final color.

❓ Predict Output

intermediate

What does this shader property code print?

This Unity C# code tries to read a float property from a material. What will it print?

Unity

using UnityEngine;

public class PropertyReader : MonoBehaviour {
    public Material mat;
    void Start() {
        if (mat.HasProperty("_Glossiness")) {
            float gloss = mat.GetFloat("_Glossiness");
            Debug.Log(gloss);
        } else {
            Debug.Log("Property not found");
        }
    }
}

A It prints "Property not found".

B It throws a NullReferenceException.

C It prints the glossiness value as a float (e.g., 0.5).

D It prints 0 always.

💡 Hint

Check if the material has the property before reading it.

If the material has the property "_Glossiness", it prints its float value. Otherwise, it prints "Property not found".

🔧 Debug

advanced

Why does this code fail to change the material color?

This Unity C# script tries to change the color of a material but the color does not update in the game. Why?

Unity

using UnityEngine;

public class ColorFail : MonoBehaviour {
    public Material mat;
    void Start() {
        mat.color = Color.blue;
    }
}

A The material is null and causes a runtime error.

B The material is shared and changes do not affect the renderer's instance.

C The script is missing a call to <code>mat.Apply()</code> to update the material.

D The color property name is incorrect; it should be "_Color".

💡 Hint

Think about how Unity handles shared materials vs instances.

Changing a shared material affects all objects using it but may not update the renderer's instance color. To change color per object, use renderer.material.color instead.

📝 Syntax

advanced

Which option correctly sets a texture property on a material?

Choose the correct Unity C# code to set a texture named "_MainTex" on a material.

A mat.SetTexture("_MainTex", myTexture);

B mat.SetTexture(myTexture, "_MainTex");

C mat.SetTexture("MainTex", myTexture);

D mat.SetTexture("_mainTex", myTexture);

💡 Hint

Check the method signature and property name case sensitivity.

The method SetTexture takes the property name as the first argument and the texture as the second. The property name is case sensitive and must include the underscore.

🚀 Application

expert

How to smoothly change a material's emission color over time?

You want to make a material's emission color fade from black to red smoothly over 3 seconds in Unity. Which code snippet achieves this?

A

void Update() {
    mat.SetColor("_EmissionColor", Color.Lerp(Color.red, Color.black, Time.time / 3f));
}

B

void Update() {
    mat.SetColor("_EmissionColor", Color.red * Time.time / 3f);
}

C

void Start() {
    mat.SetColor("_EmissionColor", Color.red);
    yield return new WaitForSeconds(3);
    mat.SetColor("_EmissionColor", Color.black);
}

D

IEnumerator FadeEmission() {
    float duration = 3f;
    float elapsed = 0f;
    while (elapsed < duration) {
        float t = elapsed / duration;
        mat.SetColor("_EmissionColor", Color.Lerp(Color.black, Color.red, t));
        elapsed += Time.deltaTime;
        yield return null;
    }
}

💡 Hint

Think about using a coroutine and Color.Lerp with elapsed time.

Option D uses a coroutine to interpolate the emission color smoothly over 3 seconds from black to red. Other options either do not interpolate correctly or reverse the colors.