game-performance

game-performance

Core Philosophy

Game performance optimization is not randomly running Unity's profiler the night before release and guessing which scripts to tweak. Real-time rendering is an unyielding mathematical budget. At 60 frames per second, the entire game engine—CPU game logic, AI pathfinding, physics simulation, audio processing, GPU vertex transformation, rasterization, and post-processing—has strictly 16.66 milliseconds to finish. At 120 FPS, that budget shrinks to 8.33 milliseconds. Hitting frame budgets requires identifying bottlenecks, managing garbage collection allocations, and optimizing draw calls.

4-Step Real-Time Performance & Profiling Architecture

Step 1: The Frame Budget Breakdown (16.66ms @ 60 FPS)

1. The Dual-Engine Budget (CPU vs GPU):
   • CPU Budget (Target: $\le 10text{ms}$):
     • Game Logic & Scripts: $\le 4text{ms}$
     • Physics Simulation: $\le 3text{ms}$
     • Render Thread / Draw Call Preparation: $\le 3text{ms}$
   • GPU Budget (Target: $\le 14text{ms}$):
     • Shadow Maps & Geometry Passes: $\le 4text{ms}$
     • Shading & Lighting Passes: $\le 6text{ms}$
     • Post-Processing & UI: $\le 4text{ms}$
2. Diagnose the Bottleneck First:
   • CPU-Bound: GPU utilization is $< 85%$; frame time drops when adding AI entities or physics objects.
   • GPU-Bound: GPU utilization is $99–100%$; frame time drops when increasing screen resolution, shadow quality, or particle density.

Step 2: CPU Optimization & Garbage Collection (GC) Defense

1. Zero-Allocation in the Hot Loop:
   • In Unity / C#, executing new inside Update(), FixedUpdate(), or LateUpdate() allocates heap memory, triggering non-deterministic Garbage Collection spikes that cause visible micro-stutters.
   • Golden Rules:
     • Cache component references in Awake() or Start() (never call GetComponent() in Update).
     • Pre-allocate reusable collections (List<T>, arrays); use list.Clear() instead of new List<T>().
     • Implement Object Pooling for all ephemeral entities (bullets, particles, sound effects, damage numbers).