How to reference a GameObject from the Scene Hierarchy in C#?

Question

I am a novice in Unity. I have a Game Object named 'courtsuit'; you can see it in my Scene Hierarchy panel here:

I added that object instance to my scene by dragging an OBJ file from my Project Assets folder into the Scene Hierarchy panel.

Now I want apply a material man to the game object at runtime. That is, when I click a button, that game object needs to change its material.

I tried and succeed by attaching a script to game object itself:

Material SphereMaterial;

// Use this for initialization
void Start()
{
    SphereMaterial = Resources.Load<Material>("Materials/man");
    if (SphereMaterial == null) Debug.Log("mat null");
    else Debug.Log("mat not null");
    Debug.Log("new Material: " + SphereMaterial.name);
    MeshRenderer meshRenderer = GetComponent<MeshRenderer>();

    // Get the current material applied on the GameObject
    Material oldMaterial = meshRenderer.material;
    Debug.Log("Applied Material: " + oldMaterial.name);
    // Set the new material on the GameObject
    meshRenderer.material = SphereMaterial;
}

But I don't know how to do this from an OnClick script on a different object, because I don't know how to locate the object in my Scene Hierarchy using C# script.

I want to do something like this:

public class ButtonHandler : MonoBehaviour {

    public void ButtonInteract()
    {
        Debug.Log("changing matriel ");
        // Change the material of the game object here

    }
}

How can I change the Game Object courtsuit's material to a material named 'man' from my Resources/Material folder using C#?

DMGregory · Accepted Answer · 2019-06-20 14:13:02Z

The simplest way is to expose a public variable of the types you want to work with:

public class MaterialChangeButtonHandler : MonoBehaviour {

    public MeshRenderer rendererToChange;
    public Material materialToChangeItTo;

    public void ButtonInteract()
    {
        rendererToChange.sharedMaterial = materialToChangeItTo;
    }
}

This will add two editable fields to the Inspector interface for this script. One for a MeshRenderer - you can drag your scene instance of your object into this field, or click the circle next to the field to choose a MeshRenderer from a list of scene objects. The other for the material to apply - you can similarly drag your material from the Assets folder, or click the circle to choose it from a list.

Referencing GameObjects and their components is covered in just about every Unity tutorial out there, so please take the time to work through some beginner's training material to get a hang of the basics of the engine. This will help you form more focused questions when you come across something the tutorials didn't cover.

RagAnt · Accepted Answer · 2019-06-21 06:25:50Z

I successfully changed material at runtime

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class ButtonHandler : MonoBehaviour {
    GameObject manObj;
    MeshRenderer m;
    // Use this for initialization
    void Start () {
        manObj= GameObject.Find("courtsuit/g_CMan0205_HD2_O01P01_S_CMan0205_HD2_O01P01_S");
        if (manObj== null) Debug.LogError("game obj null");
        else Debug.Log("game NOT null");

        m = manObj.GetComponent<MeshRenderer>();
        if (m == null) Debug.LogError("mesh obj null");
        else Debug.Log("mesh NOT null");
    }

    // Update is called once per frame
    void Update () {

    }

    public void ButtonInteract()
    {
        Debug.Log("Hello chaning matrieal ");
        Material SphereMaterial = Resources.Load<Material>("Materials/man");
        if (SphereMaterial == null) Debug.LogError("mat null");
        else Debug.Log("mat not null");
        Debug.Log("new Material: " + SphereMaterial.name);
        m.material = SphereMaterial;
    }

}

I do not recommend looking up objects by name. There are usually more robust alternatives, like storing a reference in an Inspector, or finding it via a specific marker script, or using a service locator of some variety. — DMGregory
– DMGregory ♦, Commented Jun 21, 2019 at 11:04

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