Filtering Physics Queries with Collision Profiles

Use collision profiles to dynamically filter which objects respond to physics sweeps and overlaps during complex gameplay events.

In this lesson, you will learn how to use Collision Profiles to dynamically filter which objects are detected during physics sweeps and overlaps.

The Problem: Too Much Noise

When you perform a physics query, like SweepSingleByChannel, Unreal checks every object that overlaps your trace path. If your world is cluttered with debris, pickups, and trigger volumes, your query might hit the wrong things, forcing you to write messy "if-statement" logic to ignore the objects you don't care about. Instead of filtering these objects manually in code, we use Collision Profiles to tell the physics engine to simply "not see" them in the first place.

Leveraging Collision Profiles

A Collision Profile is a pre-defined set of rules that dictates how an object responds to different Trace Channels. By setting up a specific profile, you create a "filter" that ignores unwanted collision responses before the query even registers a hit.

For instance, imagine a "Magic Shield" ability that should only block enemy projectiles, but pass through friendly allies and environment walls. Instead of checking Actor Has Tag or Class Is Child Of after a hit, you create a collision channel called Projectile and set your Shield to Overlap it, while setting your Shield's own collision profile to Ignore everything else.

Practical Implementation

When calling a physics query, you pass an FCollisionQueryParams object. You can configure this object to focus specifically on your profile's constraints:

FCollisionQueryParams QueryParams;
// Ignore the actor performing the trace so it doesn't hit itself
QueryParams.AddIgnoredActor(this);

// Use a specific Collision Profile or Trace Channel to filter results
FHitResult Hit;
bool bHit = GetWorld()->SweepSingleByChannel(
    Hit, StartLocation, EndLocation, FQuat::Identity, 
    ECC_GameTraceChannel1, // This is your pre-configured filtered channel
    FCollisionShape::MakeSphere(50.f), 
    QueryParams
);

By assigning your objects the correct Collision Profiles in the Editor, the physics engine will automatically discard irrelevant objects during the query phase, keeping your gameplay logic clean and your performance optimized.

Key Takeaway: Collision Profiles act as a physics-level filter, allowing you to refine your queries to interact only with intended object types, drastically simplifying your detection logic.