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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

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

調整後

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

只有在資料改變時在執行方法

案例1

調整前

private int m_score;  
  
public void IncrementScore(int incrementBy)  
{  
    m_score += incrementBy;  
}  
  
void Update()  
{  
    DisplayScore(m_score);  
}

調整後

private int m_score;  
  
public void IncrementScore(int incrementBy)  
{  
    m_score += incrementBy;  
    DisplayScore(m_score);  
}

案例2

調整前

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

調整後

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

避免逐幀計算 Time Slicing

調整前

void Update()  
{  
    ExampleExpensiveFunction();  
}

調整後

private int m_interval = 3;  
  
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

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

調整後

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

案例 FindObjectsOfType

調整前

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

調整後

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

案例 new List()

調整前

void Update()  
{  
    List myList = new List();  
    PopulateList(myList);  
}

調整後

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

案例 new WaitForSeconds

調整前

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

調整後

WaitForSeconds delay = new WaitForSeconds(1f);  
  
while (!isComplete)  
{  
    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

GameObject.SendMessage GameObject.BroadcastMessage UnityEngine.Object.Find() UnityEngine.Object.FindWithTag() UnityEngine.Object.FindObjectOfType() UnityEngine.Object.FindObjectsOfType() UnityEngine.Object.FindGameObjectsWithTag() Camera.main

使用 GameObject.CompareTag 取代 GameObject.tag

調整前

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

調整後

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

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]);  
}

效能差異

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]);  
}

效能差異

執行次數 100000

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

使用 FastEnum 取代 Enum

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);

效能差異 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

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;

效能差異

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

避免使用大量 MonoBehaviour

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，應使用 CoreComponent 取代。

調整前

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

調整後

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

效能差異

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);

效能差異

執行次數 100000

Time ms GC Alloc
String += 11628.02 1.32 GB
String.Concat 112.28 3.3 MB

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.Destroy(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;  
    }  
}

效能差異

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();  
    }  
}

效能差異

執行次數 10000

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

資料來源

[Fixing Performance Problems][https://learn.unity.com/tutorial/fixing-performance-problems#5c7f8528edbc2a002053b595] [對 Unity 的效能建議 - Mixed Reality][https://docs.microsoft.com/zh-tw/windows/mixed-reality/develop/unity/performance-recommendations-for-unity] [Unite 2016 - Tools, Tricks and Technologies for Reaching Stutter Free 60 FPS in INSIDE][https://www.youtube.com/watch?v=mQ2KTRn4BMI] [10000 Update() calls][https://blogs.unity3d.com/2015/12/23/1k-update-calls/] [8 Techniques to Avoid GC Pressure and Improve Performance in C# .NET][https://michaelscodingspot.com/avoid-gc-pressure/]

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