Managing Collision Response for Fractured Mesh Fragments

In this lesson, you will learn how to optimize your Geometry Collection performance by selectively managing collision responses for individual shards to ensure your game maintains a high frame rate during destruction.

When you fracture a mesh, the engine creates dozens, or even hundreds, of individual shards. If every single shard calculates complex, high-fidelity collisions against every other object, your physics thread will quickly bottleneck. To keep performance stable, you must balance visual fidelity with engine limits.

Optimizing Collision Complexity

The primary way to handle this is by adjusting the Collision Particles settings within your Geometry Collection. Instead of using a high-detail convex hull for every fragment, you can simplify the collision representation.

1. Collision Type: In your Geometry Collection asset, navigate to the Collision settings. Switch from Level Set (which is highly accurate but expensive) to Convex or Box for smaller debris shards.
2. Removal Thresholds: You can control when shards stop being a burden by using the Removal Field. By configuring your Geometry Collection to destroy or "sleep" shards that fall below a certain velocity or exist beyond a specific time, you clear them from the physics simulation before they clutter your scene.

Managing Collision Channels

You can also use collision filtering to prevent debris from colliding with unnecessary objects. For instance, tiny shards shouldn't necessarily block player movement or line traces.

In your Geometry Collection component, modify the Collision Presets. Instead of using BlockAll, create a custom preset where your fragments overlap instead of blocking your Pawn channel:

// Pseudocode for configuring a Geometry Collection Component
GeometryCollectionComp->SetCollisionResponseToChannel(ECC_Pawn, ECR_Overlap);
GeometryCollectionComp->SetCollisionResponseToChannel(ECC_Camera, ECR_Ignore);

By setting smaller fragments to Overlap or Ignore for specific channels, you prevent the physics engine from performing expensive calculations for debris that doesn't affect gameplay, allowing you to keep the physics-heavy calculations reserved for large, structural chunks.

Key Takeaway: Balance your physics budget by simplifying collision geometries and filtering unnecessary collision responses to ensure your destruction effects remain performant during high-intensity scenes.