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Unity-CSharp-Optimize-Guildline

盡可能的讓判斷條件不要在迴圈中

調整前

private void Update()  
{  
    for (int i = 0; i < array.Length; i++)  
    {  
        if (exampleBool)  
        {  
            ExampleFunction(array[i]);  
        }  
    }  
}

調整後

private void Update()  
{  
    if (exampleBool)  
    {  
        for (int i = 0; i < array.Length; i++)  
        {  
            ExampleFunction(array[i]);  
        }  
    }  
}

只有在資料改變時再執行方法

案例1

調整前

private int m_score;  
  
public void AddScore(int value)  
{  
    m_score += value;  
}  
  
private void Update()  
{  
    DisplayScore(m_score);  
}

調整後

private int m_score;  
  
public void AddScore(int value)  
{  
    m_score += value;  
    DisplayScore(m_score);  
}

案例2

調整前

private void Update()  
{  
    ExampleGarbageGeneratingFunction(transform.position.x);  
}

調整後

private float m_curPosX;
private float m_lastPosX;  
  
private void Update()  
{  
    m_curPosX = transform.position.x;  
    if (m_lastPosX != m_curPosX)  
    {
        m_lastPosX = m_curPosX;
        ExampleGarbageGeneratingFunction(m_lastPosX);  
    }  
}

避免逐幀計算

調整前

private void Update()  
{  
    ExampleExpensiveFunction();  
}

調整後

private int m_interval = 3;  
  
private void Update()  
{  
    if (Time.frameCount % m_interval == 0)  
    {  
        ExampleExpensiveFunction();  
    }  
}

使用快取

應盡量避免生成參考類型物件，即任何 new XXXXX()，否則會導致記憶體分配

案例 GetComponent

調整前

private void Update()  
{  
    Renderer renderer = GetComponent<Renderer>();  
    ExampleFunction(renderer);  
}

調整後

private Renderer m_renderer;  
  
private void Awake()  
{  
    m_renderer = GetComponent<Renderer>();  
}  
  
private void Update()  
{  
    ExampleFunction(m_renderer);  
}

案例 FindObjectsOfType

調整前

private void OnTriggerEnter(Collider other)  
{  
    Renderer[] renderers = FindObjectsOfType<Renderer>();  
    ExampleFunction(renderers);  
}

調整後

private Renderer[] m_renderers;  
  
private void Awake()  
{  
    m_renderers = FindObjectsOfType<Renderer>();  
}  
  
private void OnTriggerEnter(Collider other)  
{  
    ExampleFunction(m_renderers);  
}

案例 List

調整前

private void Update()  
{  
    List list = new List();  
    PopulateList(list);  
}

調整後

private List m_list = new List();  
void Update()  
{  
    m_list.Clear();  
    PopulateList(m_list);  
}

案例 new WaitForSeconds

調整前

while (!isDone)  
{  
    yield return new WaitForSeconds(1f);  
}

調整後

WaitForSeconds delay = new WaitForSeconds(1f);  
  
while (!isDone)  
{  
    yield return delay;  
}

案例 transform

調整前

public void UpdateCharacter()  
{  
    var lastPos = transform.position;  
    transform.position = lastPos  
        + wantedVelocity * (speed * speedFactor  
        * Mathf.Sin(someOtherFactor)  
        * drag * friction * Time.deltaTime);  
}

調整後

private Transform m_transform;  
  
private void Awake()  
{  
    m_transform = transform;  
}  
  
public void UpdateCharacter()  
{  
    var lastPos = m_transform.position;  
    m_transform.position = lastPos  
        + wantedVelocity * (speed * speedFactor  
        * Mathf.Sin(someOtherFactor)  
        * drag * friction * Time.deltaTime);  
}

案例 Time.deltaTime

調整前

public void UpdateCharacter()  
{  
    float factor = speed * speedFactor  
        * Mathf.Sin(someOtherFactor)  
        * drag * friction * Time.deltaTime;  
  
    m_lastPos.x += wantedVelocity.x * factor;  
    m_lastPos.y += wantedVelocity.y * factor;  
    m_lastPos.z += wantedVelocity.z * factor;  
    m_transform.localPosition = m_lastPos;  
}

調整後

private float m_deltaTime;  
  
public void UpdateCharacter()  
{  
    float factor = speed * speedFactor  
        * Mathf.Sin(someOtherFactor)  
        * drag * friction * m_deltaTime;  
  
    m_lastPos.x += wantedVelocity.x * factor;  
    m_lastPos.y += wantedVelocity.y * factor;  
    m_lastPos.z += wantedVelocity.z * factor;  
    m_transform.localPosition = m_lastPos;  
}

避免使用 LINQ

雖然 LINQ 簡潔易讀寫，但通常需要更多計算及記憶體配置

避免使用下列 Unity API

使用 GameObject.CompareTag 取代 GameObject.tag

調整前

private const string TAG_PLAYER = "Player";  
  
void OnTriggerEnter(Collider other)  
{  
    bool isPlayer = other.gameObject.tag == TAG_PLAYER;  
}

調整後

private const string TAG_PLAYER = "Player";  
  
void OnTriggerEnter(Collider other)  
{  
    bool isPlayer = other.gameObject.CompareTag(TAG_PLAYER);  
}

使用 yield return null 取代 yield return 0

調整前

yield return 0;

調整後

yield return null;

減少 Vector 計算

案例1

調整前

public void UpdateCharacter()  
{  
    var lastPos = transform.position;  
    transform.position = lastPos  
        + wantedVelocity * speed * speedFactor  
        * Mathf.Sin(someOtherFactor)  
        * drag * friction * Time.deltaTime;  
}

調整後

public void UpdateCharacter()  
{  
    var lastPos = transform.position;  
    transform.position = lastPos  
        + wantedVelocity * (speed * speedFactor  
        * Mathf.Sin(someOtherFactor)  
        * drag * friction * Time.deltaTime);  
}

案例2

調整前

public void UpdateCharacter()  
{  
    m_lastPos += wantedVelocity * (speed * speedFactor  
        * Mathf.Sin(someOtherFactor)  
        * drag * friction * Time.deltaTime);  
    m_transform.localPosition = m_lastPos;  
}

調整後

public void UpdateCharacter()  
{  
    float factor = speed * speedFactor  
        * Mathf.Sin(someOtherFactor)  
        * drag * friction * Time.deltaTime;  
  
    m_lastPos.x += wantedVelocity.x * factor;  
    m_lastPos.y += wantedVelocity.y * factor;  
    m_lastPos.z += wantedVelocity.z * factor;  
    m_transform.localPosition = m_lastPos;  
}

盡可能使用 Transform.localPosition

調整前

public void UpdateCharacter()  
{  
    var lastPos = m_transform.position;  
    m_transform.position = lastPos  
        + wantedVelocity * (speed * speedFactor  
        * Mathf.Sin(someOtherFactor)  
        * drag * friction * Time.deltaTime);  
}

調整後

public void UpdateCharacter()  
{  
    var lastPos = m_transform.localPosition;  
    m_transform.localPosition= lastPos  
        + wantedVelocity * (speed * speedFactor  
        * Mathf.Sin(someOtherFactor)  
        * drag * friction * Time.deltaTime);  
}

減少取得 Transform.position、Transform.localPosition

調整前

public void UpdateCharacter()  
{  
    var lastPos = m_transform.localPosition;  
    m_transform.localPosition = lastPos  
        + wantedVelocity * (speed * speedFactor  
        * Mathf.Sin(someOtherFactor)  
        * drag * friction * Time.deltaTime);  
}

調整後

private Vector3 m_lastPos = Vector3.zero;  
  
public void UpdateCharacter()  
{  
    m_lastPos += wantedVelocity * (speed * speedFactor  
        * Mathf.Sin(someOtherFactor)  
        * drag * friction * Time.deltaTime);  
    m_transform.localPosition = m_lastPos;  
}

避免使用 foreach

調整前

foreach(int value in m_list)  
{  
    DoSomething(value);  
}

調整後

int length = m_list.Count;  
for(int i = 0; i < length; i++)  
{  
    DoSomething(m_list[i]);  
}

數據比較 (執行次數 100000)

Time ms GC Alloc
foreach 28.04 48 B
for 17.47 0 B

盡量使用 Array 取代 List

調整前

int length = m_list.Count;  
for(int i = 0; i < length; i++)  
{  
    DoSomething(m_list[i]);  
}

調整後

int length = m_array.Length;  
for (int i = 0; i < length; i++)  
{  
    DoSomething(m_array[i]);  
}

數據比較 (執行次數 100000)

Time ms GC Alloc
List 17.44 0 B
Array 8.70 0 B

避免使用 Enum 函式

調整前

Enum.GetName(typeof(State), stringValue);  
Enum.GetName(typeof(State), intValue);  
Enum.GetNames(typeof(State));  
Enum.GetValues(typeof(State));  
Enum.Parse(typeof(State), stringValue);  
 
State result;  
Enum.TryParse<State>(stringValue, out result);  
 
result.ToString();

調整後

FastEnum.GetName<State>(stringValue);  
FastEnum.GetName<State>(intValue);  
FastEnum.GetNames<State>();  
FastEnum.GetValues<State>();  
FastEnum.Parse<State>(stringValue); 
 
State result;  
FastEnum.TryParse<State>(stringValue, out result);  
 
FastEnum.ToString<State>((int)result);

數據比較 (執行次數 100000)
Enum > FastEnum

Time ms GC Alloc
GetName(string) 339.60 > 18.30 1.9 MB > 0 B
GetName(int) 662.15 > 18.56 3.8 MB > 0 B
GetNames 227.57 > 12.99 3.8 MB > 0 B
GetValues 821.96 > 15.63 8.8 MB > 1.0 KB
Parse 765.91 > 184.60 12.2 MB > 0 B
TryParse 761.73 > 185.73 12.2 MB > 0 B
ToString 579.02 > 18.10 3.8 MB > 0 B

避免使用屬性 Property

屬性 Property 底層依然是透過方法實現，使用 Property 會導致執行效能較差，但使用上及維護上會較為方便，能夠針對 get 或 set 設置不同的訪問層級和檢查機制，且支援任何方法的語言特性，如 virtual、abstract。

調整前

public int intValue { get; set; }

調整後

public int intValue;

數據比較 (執行次數 1000000)

Time ms GC Alloc
Property 41.00 0 B
Field 0 0 B

使用 is 或 as 而不是強制類型轉換

is: 能夠檢查一個對象是否兼容於其他指定類型，回傳一個 Bool 值且不會跳出異常
as: 作用跟強制類型轉換一樣，但不會跳出異常，如果轉換失敗，會回傳 null

避免大量使用 MonoBehaviour.Update、FixedUpdate、LateUpdate

由於 Unity MonoBehaviour 使用的是 Messaging System，能夠讓開發者在 MonoBehaviour 中自行定義特殊方法，如: Awake、Start、Update、FixedUpdate、LateUpdate 等。
當有使用大量 MonoBehaviour.Update、FixedUpdate、LateUpdate 需求時，應自定義功能取代。

調整前

using UnityEngine;  
public class TestMonoBehaviour : MonoBehaviour  
{  
    private int m_count;  
    private void Update()  
    {  
        m_count++;  
    }  
}

調整後

public class TestOptimizedMonoBehaviour : CoreComponent 
{  
    private int m_count;  
    public override void Tick(float deltaTime, float unscaledDeltaTime)  
    {  
        m_count++;  
    }  
}

數據比較 (執行次數 10000)

Time ms GC Alloc
MonoBehaviour 4.01 0 B
CoreComponent 1.82 0 B

大量字元串接時使用 String.Concat

調整前

char c = 'X';  
string output = string.Empty;  
for(int i = 0; i < stringLength; i++)  
{  
    output += c;  
}

調整後

char c = 'X';  
char[] chars = new char[stringLength];  
for (int i = 0; i < stringLength; i++)  
{  
    chars[i] = c;  
}  
  
string output = string.Concat(chars);

數據比較 (執行次數 100000)

Time ms GC Alloc
String += 11723.20 1.32 GB
String.Concat 27.50 3.3 MB

大量字串串接時使用 StringBuilder.Append

調整前 - String +=

string output = string.Empty;
for(int i = 0; i < count; i++)
{
    output += value;
}

調整前 - String.Format

private const string FORMAT = "{0}{1}";
string output = string.Empty;
for (int i = 0; i < count; i++)
{
    output = string.Format(FORMAT, output, value);
}

調整後

m_stringBuilder.Clear();
for (int i = 0; i < count; i++)
{
    m_stringBuilder.Append(value);
}

string output = m_stringBuilder.ToString();

數據比較 (執行次數 10000)

Time ms GC Alloc
String += 563.65 477.1 MB
String.Format 1331.72 1.07 GB
StringBuilder.Append 0.48 97.7 KB

生成大量相同物件使用 Object Pool

調整前

GameObject instance = GameObject.Instantiate(m_prefab);  
GameObject.Destroy(instance);

調整後

GameObject instance = PoolManager.Instance.Get(m_prefab);  
PoolManager.Instance.Recycle(instance);

使用 struct 取代 class

調整前

class VectorClass  
{  
    public int X { get; set; }  
    public int Y { get; set; }  
}  
  
private void Execute()  
{  
    VectorClass[] vectors = new VectorClass[10000];  
    for (int i = 0; i < vectors.Length; i++)  
    {  
        vectors[i] = new VectorClass();  
        vectors[i].X = 5;  
        vectors[i].Y = 10;  
    }  
}

調整後

struct VectorStruct  
{  
    public int X { get; set; }  
    public int Y { get; set; }  
}  
  
private void Execute()  
{  
    VectorStruct[] vectors = new VectorStruct[10000];  
    for (int i = 0; i < vectors.Length; i++)  
    {  
        vectors[i].X = 5;  
        vectors[i].Y = 10;  
    }  
}

數據比較 (執行次數 10000)

Time ms GC Alloc
class 5.68 312.5 KB
struct 2.00 78.2 KB

避免使用解構子

調整前

class SimpleWithFinalizer  
{  
    public int x { get; set; }  
  
    ~SimpleWithFinalizer()  
    {  
  
    }  
}  
  
private void Execute()  
{  
    for (int i = 0; i < 10000; i++)  
    {  
        new SimpleWithFinalizer();  
    }  
}

調整後

class Simple  
{  
    public int x { get; set; }  
}  
  
private void Execute()  
{  
    for (int i = 0; i < 10000; i++)  
    {  
        new Simple();  
    }  
}

數據比較 (執行次數 10000)

Time ms GC Alloc
有解構子 4.48 195.3 KB
沒有解構子 2.14 195.3 KB

盡可能預先快取組件

調整前

[SerializeField] protected Transform m_transform = null;
[SerializeField] protected RectTransform m_rectTransform = null;
[SerializeField] protected Canvas m_canvas = null;
[SerializeField] protected CanvasScaler m_canvasScaler = null;
[SerializeField] protected GraphicRaycaster m_graphicRaycaster = null;
[SerializeField] protected CanvasGroup m_canvasGroup = null;
[SerializeField] protected ScrollRect[] m_scrollRects = null;
[SerializeField] protected InputField[] m_inputFields = null;

private void Awake()
{
    m_transform = transform;
    m_rectTransform = GetComponent<RectTransform>();
    m_canvas = GetComponent<Canvas>();
    m_canvasScaler = GetComponent<CanvasScaler>();
    m_graphicRaycaster = GetComponent<GraphicRaycaster>();
    m_canvasGroup = GetComponent<CanvasGroup>();
    m_scrollRects = GetComponentsInChildren<ScrollRect>(true);
    m_inputFields = GetComponentsInChildren<InputField>(true);
}

調整後

[SerializeField] protected Transform m_transform = null;
[SerializeField] protected RectTransform m_rectTransform = null;
[SerializeField] protected Canvas m_canvas = null;
[SerializeField] protected CanvasScaler m_canvasScaler = null;
[SerializeField] protected GraphicRaycaster m_graphicRaycaster = null;
[SerializeField] protected CanvasGroup m_canvasGroup = null;
[SerializeField] protected ScrollRect[] m_scrollRects = null;
[SerializeField] protected InputField[] m_inputFields = null;

protected override void CacheComponents()
{
    CacheComponent(ref m_transform);
    CacheComponent(ref m_rectTransform);
    CacheComponent(ref m_canvas);
    CacheComponent(ref m_canvasScaler);
    CacheComponent(ref m_graphicRaycaster);
    CacheComponent(ref m_canvasGroup);
    CacheComponentsInChildren(ref m_scrollRects, true);
    CacheComponentsInChildren(ref m_inputFields, true);
}

看不到物件時，關閉不需要執行的組件

當物件存在於場景中，即使物件在可視範圍之外其身上的組件也會持續運作，當這類組件的數量變多時，就會開始影響遊戲性能。
建議當物件在視錐體之外或沒有顯示在畫面上時，關閉將下列組件。

  • CanvasScaler
  • ScrollRect
  • InputField
  • DynamicBone
  • 其他任何昂貴的 MonoBehaviour

設定 Shader 參數時，使用 PropertyToID

Unity 執行後會給予 Shader 參數名稱一個唯一的識別符。
比起使用參數名稱傳遞資料，使用 Shader.PropertyToID 更為高效。

調整前

private const string _Color = "_Color";
private void SetColor(Color value)
{
    m_material.SetColor(_Color, value);
}

調整後

private readonly int _Color = Shader.PropertyToID("_Color");
private void SetColor(Color value)
{
    m_material.SetColor(_Color, value);
}

數據比較 (執行次數 100000)

Time ms GC Alloc
Material.SetColor(string name, Color value) 44.38 0 B
Material.SetColor(int nameID, Color value) 29.83 0 B

設定 Animator 參數時，使用 StringToHash

同理 Shader.PropertyToID，使用 Animator.StringToHash 更為高效。

調整前

private const string _BoolParameterName = "_BoolParameterName";
private void SetBoolParameter(bool value)
{
    m_animator.SetBool(_BoolParameterName, value);
}

調整後

private readonly int _BoolParameterName = Animator.StringToHash("_BoolParameterName");
private void SetBoolParameter(bool value)
{
    m_animator.SetBool(_BoolParameterName, value);
}

數據比較 (執行次數 100000)

Time ms GC Alloc
Animator.SetBool(string name, bool value) 19.86 0 B
Animator.SetBool(int nameID, bool value) 16.78 0 B

預先定義 List 或 Dictionary 的初始化大小

調整前

private void InitializeList(int count)
{
    m_list = new List<int>();
    for(int i = 0; i < count; i++)
    {
        m_list.Add(i);
    }
}

private void InitializeDictionary(int count)
{
    m_dictionary = new Dictionary<int, int>();
    for(int i = 0; i < count; i++)
    {
        m_dictionary.Add(i, i);
    }
}

調整後

private void InitializeList(int count)
{
    m_list = new List<int>(count);
    for(int i = 0; i < count; i++)
    {
        m_list.Add(i);
    }
}

private void InitializeDictionary(int count)
{
    m_dictionary = new Dictionary<int, int>(count);
    for(int i = 0; i < count; i++)
    {
        m_dictionary.Add(i, i);
    }
}

數據比較 (執行次數 100000)

Time ms GC Alloc
List 無初始化大小 16.77 1.0 MB
List 有初始化大小 8.72 390.7 KB
Dictionary 無初始化大小 40.42 5.8 MB
Dictionary 有初始化大小 36.50 2.1 MB

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