eng-unity-mobile-optimization

Unity Mobile Optimization

Overview

Mobile platforms have unique constraints: limited memory, battery life, thermal throttling, and variable hardware. This skill covers mobile-specific optimization techniques.

When to Use

• iOS and Android development
• Battery-sensitive applications
• Memory-constrained devices
• Thermal management
• Variable quality settings

Memory Management

Memory Budget System

public class MobileMemoryManager : MonoBehaviour
{
    [SerializeField] private long _warningThresholdMB = 800;
    [SerializeField] private long _criticalThresholdMB = 1000;
    
    public event Action OnMemoryWarning;
    public event Action OnMemoryCritical;
    
    private void Awake()
    {
        // iOS memory warning callback
        Application.lowMemory += OnLowMemory;
    }
    
    private void OnDestroy()
    {
        Application.lowMemory -= OnLowMemory;
    }
    
    private void OnLowMemory()
    {
        Debug.LogWarning("Low memory warning received");
        OnMemoryCritical?.Invoke();
        
        // Emergency cleanup
        Resources.UnloadUnusedAssets();
        GC.Collect();
    }
    
    public MemoryStatus GetMemoryStatus()
    {
        long usedMB = Profiler.GetTotalAllocatedMemoryLong() / 1_000_000;
        
        if (usedMB >= _criticalThresholdMB)
            return MemoryStatus.Critical;
        if (usedMB >= _warningThresholdMB)
            return MemoryStatus.Warning;
        return MemoryStatus.Normal;
    }
    
    public void RequestCleanup()
    {
        // Aggressive cleanup
        StartCoroutine(CleanupRoutine());
    }
    
    private IEnumerator CleanupRoutine()
    {
        // Unload unused assets
        var operation = Resources.UnloadUnusedAssets();
        yield return operation;
        
        // GC with minimal pause
        GC.Collect(0, GCCollectionMode.Optimized);
        yield return null;
        
        GC.Collect(1, GCCollectionMode.Optimized);
    }
}

public enum MemoryStatus { Normal, Warning, Critical }

Texture Memory Control

public class TextureMemoryController
{
    public static void SetQualityForDevice(DeviceTier tier)
    {
        switch (tier)
        {
            case DeviceTier.Low:
                QualitySettings.globalTextureMipmapLimit = 2; // 1/4 resolution
                QualitySettings.anisotropicFiltering = AnisotropicFiltering.Disable;
                break;
                
            case DeviceTier.Medium:
                QualitySettings.globalTextureMipmapLimit = 1; // 1/2 resolution
                QualitySettings.anisotropicFiltering = AnisotropicFiltering.Enable;
                break;
                
            case DeviceTier.High:
                QualitySettings.globalTextureMipmapLimit = 0; // Full resolution
                QualitySettings.anisotropicFiltering = AnisotropicFiltering.ForceEnable;
                break;
        }
    }
    
    public static void ForceReduceTextureMemory()
    {
        // Increase mipmap limit temporarily
        QualitySettings.globalTextureMipmapLimit++;
        
        // Force GPU to release memory
        Resources.UnloadUnusedAssets();
    }
}

Battery Optimization

Frame Rate Control

public class BatteryOptimizer : MonoBehaviour
{
    [SerializeField] private int _highPerformanceFps = 60;
    [SerializeField] private int _balancedFps = 30;
    [SerializeField] private int _batterySaverFps = 24;
    
    private PerformanceMode _currentMode = PerformanceMode.Balanced;
    
    public void SetPerformanceMode(PerformanceMode mode)
    {
        _currentMode = mode;
        
        switch (mode)
        {
            case PerformanceMode.HighPerformance:
                Application.targetFrameRate = _highPerformanceFps;
                QualitySettings.vSyncCount = 0;
                break;
                
            case PerformanceMode.Balanced:
                Application.targetFrameRate = _balancedFps;
                QualitySettings.vSyncCount = 1;
                break;
                
            case PerformanceMode.BatterySaver:
                Application.targetFrameRate = _batterySaverFps;
                QualitySettings.vSyncCount = 2;
                // Additional battery saving
                Screen.brightness = 0.5f;
                break;
        }
    }
    
    public void SetAdaptiveFrameRate(bool inCombat)
    {
        // Dynamic frame rate based on gameplay
        if (inCombat)
        {
            Application.targetFrameRate = _highPerformanceFps;
        }
        else
        {
            Application.targetFrameRate = _balancedFps;
        }
    }
}

public enum PerformanceMode { HighPerformance, Balanced, BatterySaver }

Background Behavior

public class BackgroundHandler : MonoBehaviour
{
    private bool _wasInBackground;
    
    private void OnApplicationPause(bool pauseStatus)
    {
        if (pauseStatus)
        {
            // Going to background
            OnEnterBackground();
        }
        else
        {
            // Returning from background
            OnExitBackground();
        }
        
        _wasInBackground = pauseStatus;
    }
    
    private void OnEnterBackground()
    {
        // Pause audio
        AudioListener.pause = true;
        
        // Stop expensive updates
        Time.timeScale = 0;
        
        // Release non-essential resources
        Resources.UnloadUnusedAssets();
    }
    
    private void OnExitBackground()
    {
        AudioListener.pause = false;
        Time.timeScale = 1;
        
        // Check if device overheated while backgrounded
        CheckThermalState();
    }
}

Thermal Management

Thermal State Monitoring

public class ThermalManager : MonoBehaviour
{
    public event Action<ThermalState> OnThermalStateChanged;
    
    private ThermalState _currentState = ThermalState.Normal;
    private float _checkInterval = 5f;
    
    private void Start()
    {
        InvokeRepeating(nameof(CheckThermalState), 0, _checkInterval);
    }
    
    private void CheckThermalState()
    {
#if UNITY_IOS
        var newState = GetIOSThermalState();
#elif UNITY_ANDROID
        var newState = GetAndroidThermalState();
#else
        var newState = ThermalState.Normal;
#endif
        
        if (newState != _currentState)
        {
            _currentState = newState;
            OnThermalStateChanged?.Invoke(newState);
            ApplyThermalMitigation(newState);
        }
    }
    
#if UNITY_IOS
    private ThermalState GetIOSThermalState()
    {
        // iOS provides thermal state via native plugin
        // ProcessInfo.ThermalState
        return ThermalState.Normal; // Implement native plugin
    }
#endif
    
#if UNITY_ANDROID
    private ThermalState GetAndroidThermalState()
    {
        // Android thermal API (API 29+)
        // PowerManager.getCurrentThermalStatus()
        return ThermalState.Normal; // Implement native plugin
    }
#endif
    
    private void ApplyThermalMitigation(ThermalState state)
    {
        switch (state)
        {
            case ThermalState.Normal:
                // Full performance
                Application.targetFrameRate = 60;
                QualitySettings.SetQualityLevel(2);
                break;
                
            case ThermalState.Fair:
                // Slight reduction
                Application.targetFrameRate = 45;
                break;
                
            case ThermalState.Serious:
                // Significant reduction
                Application.targetFrameRate = 30;
                QualitySettings.SetQualityLevel(1);
                break;
                
            case ThermalState.Critical:
                // Emergency mode
                Application.targetFrameRate = 24;
                QualitySettings.SetQualityLevel(0);
                ShowThermalWarning();
                break;
        }
    }
    
    private void ShowThermalWarning()
    {
        Debug.LogWarning("Device overheating - reducing performance");
        // Show UI warning to user
    }
}

public enum ThermalState { Normal, Fair, Serious, Critical }

Device Tier Detection

Hardware Classification

public class DeviceClassifier
{
    public static DeviceTier ClassifyDevice()
    {
        int systemMemoryMB = SystemInfo.systemMemorySize;
        int processorCount = SystemInfo.processorCount;
        int graphicsMemoryMB = SystemInfo.graphicsMemorySize;
        
        // Calculate tier based on specs
        int score = 0;
        
        // Memory score
        if (systemMemoryMB >= 6000) score += 3;
        else if (systemMemoryMB >= 4000) score += 2;
        else if (systemMemoryMB >= 2000) score += 1;
        
        // CPU score
        if (processorCount >= 8) score += 3;
        else if (processorCount >= 6) score += 2;
        else if (processorCount >= 4) score += 1;
        
        // GPU score
        if (graphicsMemoryMB >= 4000) score += 3;
        else if (graphicsMemoryMB >= 2000) score += 2;
        else if (graphicsMemoryMB >= 1000) score += 1;
        
        // Classify
        if (score >= 7) return DeviceTier.High;
        if (score >= 4) return DeviceTier.Medium;
        return DeviceTier.Low;
    }
    
    public static void LogDeviceInfo()
    {
        Debug.Log($"Device: {SystemInfo.deviceModel}");
        Debug.Log($"OS: {SystemInfo.operatingSystem}");
        Debug.Log($"RAM: {SystemInfo.systemMemorySize}MB");
        Debug.Log($"CPU: {SystemInfo.processorType} x{SystemInfo.processorCount}");
        Debug.Log($"GPU: {SystemInfo.graphicsDeviceName} ({SystemInfo.graphicsMemorySize}MB)");
        Debug.Log($"Tier: {ClassifyDevice()}");
    }
}

public enum DeviceTier { Low, Medium, High }

Quality Presets

public class QualityPresetManager
{
    public static void ApplyPresetForTier(DeviceTier tier)
    {
        var preset = GetPreset(tier);
        
        // Graphics
        QualitySettings.SetQualityLevel(preset.QualityLevel);
        QualitySettings.shadows = preset.Shadows;
        QualitySettings.shadowResolution = preset.ShadowResolution;
        QualitySettings.antiAliasing = preset.AntiAliasing;
        
        // Rendering
        QualitySettings.pixelLightCount = preset.PixelLights;
        QualitySettings.globalTextureMipmapLimit = preset.TextureMipLevel;
        
        // Performance
        Application.targetFrameRate = preset.TargetFps;
        
        // Physics
        Time.fixedDeltaTime = 1f / preset.PhysicsRate;
        
        Debug.Log($"Applied quality preset for {tier}: {preset.QualityLevel}");
    }
    
    private static QualityPreset GetPreset(DeviceTier tier)
    {
        return tier switch
        {
            DeviceTier.Low => new QualityPreset
            {
                QualityLevel = 0,
                Shadows = ShadowQuality.Disable,
                ShadowResolution = ShadowResolution.Low,
                AntiAliasing = 0,
                PixelLights = 1,
                TextureMipLevel = 2,
                TargetFps = 30,
                PhysicsRate = 30
            },
            DeviceTier.Medium => new QualityPreset
            {
                QualityLevel = 2,
                Shadows = ShadowQuality.HardOnly,
                ShadowResolution = ShadowResolution.Medium,
                AntiAliasing = 2,
                PixelLights = 2,
                TextureMipLevel = 1,
                TargetFps = 45,
                PhysicsRate = 45
            },
            _ => new QualityPreset
            {
                QualityLevel = 4,
                Shadows = ShadowQuality.All,
                ShadowResolution = ShadowResolution.High,
                AntiAliasing = 4,
                PixelLights = 4,
                TextureMipLevel = 0,
                TargetFps = 60,
                PhysicsRate = 60
            }
        };
    }
    
    private struct QualityPreset
    {
        public int QualityLevel;
        public ShadowQuality Shadows;
        public ShadowResolution ShadowResolution;
        public int AntiAliasing;
        public int PixelLights;
        public int TextureMipLevel;
        public int TargetFps;
        public int PhysicsRate;
    }
}

Render Pipeline Optimization

Dynamic Resolution

public class DynamicResolutionController : MonoBehaviour
{
    [SerializeField] private float _targetFrameTime = 16.67f; // 60 FPS
    [SerializeField] private float _minScale = 0.5f;
    [SerializeField] private float _maxScale = 1f;
    
    private float _currentScale = 1f;
    private float _smoothedFrameTime;
    
    private void Update()
    {
        // Smooth frame time
        float frameTime = Time.unscaledDeltaTime * 1000f;
        _smoothedFrameTime = Mathf.Lerp(_smoothedFrameTime, frameTime, 0.1f);
        
        // Adjust scale
        if (_smoothedFrameTime > _targetFrameTime * 1.2f)
        {
            // Too slow - reduce resolution
            _currentScale = Mathf.Max(_minScale, _currentScale - 0.05f);
        }
        else if (_smoothedFrameTime < _targetFrameTime * 0.8f)
        {
            // Room for improvement - increase resolution
            _currentScale = Mathf.Min(_maxScale, _currentScale + 0.02f);
        }
        
        ScalableBufferManager.ResizeBuffers(_currentScale, _currentScale);
    }
}

LOD Bias

public class LODController
{
    public static void SetLODForTier(DeviceTier tier)
    {
        switch (tier)
        {
            case DeviceTier.Low:
                QualitySettings.lodBias = 0.5f;
                QualitySettings.maximumLODLevel = 1;
                break;
                
            case DeviceTier.Medium:
                QualitySettings.lodBias = 1f;
                QualitySettings.maximumLODLevel = 0;
                break;
                
            case DeviceTier.High:
                QualitySettings.lodBias = 1.5f;
                QualitySettings.maximumLODLevel = 0;
                break;
        }
    }
}

Best Practices

1. Profile on actual devices - Not just Editor
2. Set memory budgets per device tier
3. Monitor thermal state and adapt
4. Use dynamic frame rate based on gameplay
5. Implement quality tiers automatically
6. Handle background/foreground transitions
7. Pool and reuse everything
8. Compress textures appropriately
9. Limit draw calls to <100 on low-end
10. Test on minimum spec devices

Troubleshooting

Issue	Solution
App killed by OS	Reduce memory, handle lowMemory
Device overheating	Monitor thermal, reduce quality
Battery drain	Lower frame rate, disable features
Stuttering	Profile GC, use pools
Long load times	Stream assets, show progress
Crash on low-end	Test minimum spec, reduce quality