Unity Performance

Unity Performance Optimization

Overview

Systematic approach to profiling and optimizing Unity games. Covers profiling tools, CPU/GPU optimization, memory management, rendering optimization, and platform-specific considerations.

Profiling Tools

Profiler Workflow

1. Build with Development Build + Autoconnect Profiler enabled
2. Profile on target device (not in Editor -- Editor overhead distorts results)
3. Identify the bottleneck category: CPU-bound, GPU-bound, or memory pressure
4. Drill into the specific system causing the issue
5. Optimize, re-profile, and compare

Reading the Profiler

If frame time > 16.6ms (60 FPS target):
  CPU timeline > GPU timeline -> CPU-bound
  GPU timeline > CPU timeline -> GPU-bound
  GC.Alloc column shows per-frame allocations -> GC pressure

Look for spikes (single bad frames) vs. sustained high times (baseline too heavy).

CPU Optimization

Reduce Per-Frame Allocations (GC)

Object Pooling

public class ObjectPool<T> where T : Component
{
    readonly Queue<T> _pool = new();
    readonly T _prefab;
    readonly Transform _parent;

    public ObjectPool(T prefab, int preWarm, Transform parent = null)
    {
        _prefab = prefab;
        _parent = parent;
        for (int i = 0; i < preWarm; i++)
            _pool.Enqueue(CreateInstance());
    }

    public T Get(Vector3 position, Quaternion rotation)
    {
        var obj = _pool.Count > 0 ? _pool.Dequeue() : CreateInstance();
        obj.transform.SetPositionAndRotation(position, rotation);
        obj.gameObject.SetActive(true);
        return obj;
    }

    public void Return(T obj)
    {
        obj.gameObject.SetActive(false);
        _pool.Enqueue(obj);
    }

    T CreateInstance()
    {
        var obj = Object.Instantiate(_prefab, _parent);
        obj.gameObject.SetActive(false);
        return obj;
    }
}

Pool bullets, particles, enemies, UI elements -- anything instantiated/destroyed frequently. Unity 2021+ also has UnityEngine.Pool.ObjectPool<T> built-in.

Update Optimization

GPU / Rendering Optimization

Draw Call Reduction

LOD (Level of Detail)

LOD Group Setup:
  LOD 0 (0-30%):  Full-detail mesh (5000 tris)
  LOD 1 (30-60%): Medium mesh (2000 tris)
  LOD 2 (60-90%): Low mesh (500 tris)
  Culled (90%+):  Not rendered

Use LOD for meshes, but also reduce script complexity, particle counts, and physics at distance.

Occlusion Culling

Bake occlusion data for indoor/complex scenes. Mark large static occluders (walls, floors). Configure cell size based on scene scale. Use the Occlusion Culling window to visualize and test.

Shader Optimization

Memory Management

Common Memory Issues

Texture Compression Per Platform

Use "Override for [Platform]" in texture import settings. Set max texture size to the minimum needed (512 for UI icons, 1024 for props, 2048 for hero assets).

Platform-Specific Considerations

Addressables and Asset Loading

Use Addressables for async asset loading to avoid load-time hitches:

// Preload during loading screen
var handle = Addressables.LoadAssetAsync<GameObject>("enemy_boss");
await handle;

// Release when done
Addressables.Release(handle);

Use Addressable groups to control bundle granularity. Mark infrequently used assets as remote/on-demand. Profile bundle memory with the Addressables Event Viewer.

Quick Optimization Checklist

• Profile on target device, not in Editor
• Zero per-frame GC allocations in gameplay code
• Object pooling for all frequently spawned objects
• Static batching enabled for non-moving objects
• LOD groups on all 3D models visible at varying distances
• Textures compressed per platform with appropriate max sizes
• Disable Read/Write on meshes and textures not modified at runtime
• Audio clips use appropriate compression settings
• Occlusion culling baked for indoor/complex scenes
• Shader variants stripped in build settings

Additional Resources

Reference Files

• references/profiling-deep-dive.md -- Advanced Profiler usage, memory profiler snapshots, frame-by-frame analysis, custom profiler markers, automated performance testing, build size analysis, ECS/DOTS performance patterns