Epic Games Engineers Reveal the 7 Causes of Unreal Engine Issues

Unraveling The Top 7 PC Performance Challenges in Unreal Engine Games at Unreal Fest 2025

During Unreal Fest 2025 in Orlando, Epic Games Senior Engineer Ari Arnbjornsson delivered a session titled "The Great Hitch Hunt." The presentation addressed common stuttering and freezing issues in PC games developed with Unreal Engine, pinpointing their primary causes and offering practical solutions. Arnbjornsson outlined seven key performance challenges in Unreal Engine-powered games. A primary cause is level streaming, which dynamically loads and unloads parts of the game world. Overusing individual objects (e.g., tables or books) instead of optimized structures like Static Meshes Instanced (SMIs) can strain the graphics engine's memory and the garbage collection system. Epic Games is experimenting with solutions, such as Cell Transformers in Unreal Engine 5.5, which aims to automatically correct this issue during gameplay. Physics also poses a significant challenge. Arnbjornsson clarified that the Nanite system does not automatically handle collision simplification, contrary to some developers' beliefs. He advised using simple shapes (e.g., spheres and boxes) for collisions whenever possible and disabling collisions for distant objects that do not require interaction. While Epic is testing asynchronous physics reset, it is not yet recommended for commercial games.

Optimizing Unreal Engine Performance: Addressing 5 Challenges in PC Gaming

Another concern is the creation of characters and objects. Generating complex characters with multiple parts, especially in large quantities, can cause performance drops. Potential solutions include limiting the number of creations per frame or recycling existing actors through actor pooling. Although not a built-in engine feature, this approach may become more viable in the future. Pipeline State Object (PSO) compilations can create bottlenecks, particularly on PCs due to hardware diversity, in contrast to the more straightforward process on consoles. Epic addresses this by precaching PSOs in Unreal Engine 5.3 and providing tools like the PSO Cache Buster to help studios detect and optimize these issues proactively. Garbage collection, if not managed efficiently, can cause delays when numerous unused objects accumulate. Epic is developing incremental accessibility analysis and multithreaded garbage collection to mitigate these impacts. The fifth issue involves synchronous loading of resources, which halts the game's main process until a file fully loads, leading to execution delays. Arnbjornsson recommended exclusively using asynchronous loading and highlighted tools designed to identify and eliminate related bottlenecks.

Enhancing Unreal Performance: Tackling Blueprint Complexity with Unreal Insights Tool

Finally, excessive logic within Blueprints, such as complex timers and animations, can cause system instability. Epic plans to enhance the Unreal Insights tool to assist developers in identifying and resolving these problems. Arnbjornsson's presentation served as a crucial technical reminder for production teams: despite advancements in hardware and Unreal Engine updates, active optimization and clever workarounds for engine limitations remain essential. Epic anticipates that adherence to these guidelines will lead to significant performance improvements, especially for PC games built with the engine.

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