【Unreal Engine】Creating Custom Collision Channels and Profiles

The Need for Custom Collision

When starting game development with Unreal Engine (UE), the default collision channels like WorldStatic and Pawn may be sufficient. However, as game complexity increases, you'll quickly hit walls.

Specific problem examples:

• "I want only certain types of weapon bullets to be blocked by specific enemy shields"
• "I want to create an invisible trigger zone that only the player character reacts to"
• "I want to distinguish between environmental objects (e.g., destructible walls) and other static objects (e.g., ground)"

Such fine control like "special processing only when object A collides with object B" cannot be achieved with generic channels alone. Setting everything to Block or Overlap causes unintended collisions and performance degradation.

This article thoroughly explains custom collision channels and collision profiles for solving these challenges, for beginners to intermediate developers. Mastering these will make your game's collision detection logic clearer and more efficiently manageable.

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Roles of Collision Channels and Profiles

To understand custom collision, you first need to clearly distinguish between "channels" and "profiles."

1. Collision Channel

A collision channel is like a "tag" for identifying object types. In UE, there are mainly two types:

Channel Type	Role	Main Use
Object Channel	Defines "what the object itself is."	Set on components like Static Mesh, Skeletal Mesh, Character.
Trace Channel	Defines "what queries like raycasts or shape traces want to detect."	Used for line-of-sight checks, weapon hit detection, environment scanning.

By default, channels like WorldStatic, Pawn, PhysicsBody are provided, but you can add up to 18 custom channels in project settings.

2. Collision Profile

A collision profile is a preset that bundles response settings for object channels.

For example, assume an actor with a "Player" object channel. Applying a collision profile called "Default Pawn" to this actor automatically applies the responses defined in that profile (e.g., Block for WorldStatic, Overlap for Projectile).

Collision Profile Components:

• Object Type: The channel of the object itself with this profile (e.g., Pawn).
• Collision Responses: List of responses (Ignore, Overlap, Block) to all other object channels (including custom channels).

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Creating Custom Channels Step by Step

To implement complex logic, first create custom channels. Here we'll create channels to distinguish "player shields" and "enemy bullets."

Step 1: Open Project Settings

Open Edit -> Project Settings and navigate to Engine -> Collision section.

Step 2: Add New Object Channels

In the Object Channels section, click New Object Channel... and add the following channels:

Channel Name	Default Response	Notes
Player_Shield	Block	Set on player shield components.
Enemy_Projectile	Ignore	Set on enemy bullet components.

Importance of Default Response: The default response set here is applied when response to that channel isn't explicitly defined in a profile. Normally set to Ignore and override to Block or Overlap only in necessary profiles is the best practice.

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Creating Custom Profiles

Next, create collision profiles to utilize the custom channels.

Step 1: Create New Presets (Profiles)

In the Preset section, click New and create the following two profiles.

Profile 1: Shield_Active

This profile is applied to the player's shield component.

Setting Item	Value
Preset Name	Shield_Active
Collision Enabled	Query and Physics
Object Type	Player_Shield (← custom channel created earlier)

Collision Responses Settings:

Channel	Response	Reason
Enemy_Projectile	Block	Enemy bullets are blocked by shield.
Pawn	Overlap	Player itself passes through shield.
WorldStatic	Ignore	Shield isn't affected by environment.
Others	Ignore	Ignore unnecessary ones for performance.

Profile 2: Enemy_Bullet

This profile is applied to enemy bullet components.

Setting Item	Value
Preset Name	Enemy_Bullet
Collision Enabled	Query Only (if physics simulation not needed)
Object Type	Enemy_Projectile (← custom channel created earlier)

Collision Responses Settings:

Channel	Response	Reason
Player_Shield	Block	Bullets collide with and stop at shield.
Pawn	Overlap	Overlap for damage processing when hitting player body.
WorldStatic	Block	Bullets hit walls and ground.

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Applying in Blueprint and C++

Collision profiles can be set in the Details panel of components like Static Mesh Component or Capsule Component, but can also be changed dynamically during gameplay.

Applying in Blueprint

To switch collision profiles on specific events (e.g., shield activation), use the Set Collision Profile Name node.

1. Select target component (e.g., ShieldMesh).
2. Call Set Collision Profile Name node.
3. Enter the created profile name (e.g., Shield_Active) exactly in In Profile Name.

// Blueprint pseudo-code
// Event: Shield Activation
-> ShieldMesh (StaticMeshComponent)
   -> Set Collision Profile Name (In Profile Name: "Shield_Active")

💡 About Set Collision Profile Name Node

This node only takes the In Profile Name parameter. The profile name must be a string exactly matching the name defined in project settings. If a non-existent profile name is specified, a warning log is output and collision settings won't change.

Applying in C++

To initially set or dynamically change component collision profiles in C++, use the SetCollisionProfileName function.

// C++ initial setup example (in constructor, etc.)
// MyShieldComponent is UStaticMeshComponent* or other collision-enabled component
MyShieldComponent->SetCollisionProfileName(TEXT("Shield_Active"));

// C++ dynamic change example (in specific function, etc.)
void AMyCharacter::ActivateShield()
{
    // Specify profile name with FName
    static const FName ShieldProfile(TEXT("Shield_Active"));
    MyShieldComponent->SetCollisionProfileName(ShieldProfile);
}

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Best Practices and Common Mistakes

✅ Best Practices

1. Keep Channels to a Minimum: Custom channels are limited to 18, and more channels make response management complex and affect performance. Always ask yourself "Is this channel necessary for logic that can't be achieved otherwise?"
2. Adopt Clear Naming Conventions: Don't use ambiguous names like Custom1, Custom2; use purpose-clear names like Weapon_Laser, Destructible_Wall.
3. Centralize with Profiles: Rather than directly modifying individual response settings (Custom...) on actors or components, create collision profiles (Presets) and apply them to prevent setting errors and simplify management.

❌ Common Mistakes

1. Confusing Object Type and Trace Channel:
   • Mistake: Set bullet component's Object Type to Pawn, and set raycast's Trace Channel to Enemy_Projectile.
   • Correct: Bullet component's Object Type should be Enemy_Projectile, and raycast should trace channels you want to detect (e.g., Pawn or WorldStatic).
2. Excessive Block Responses:
   • Mistake: Set all custom channel responses to Block by default.
   • Result: Unintended objects collide, causing weird physics behavior and performance degradation. Keep Ignore as default and set Block or Overlap only for necessary combinations.
3. Forgetting to Apply Custom Channels:
   • Mistake: Create custom channels in project settings but leave actual actor component Object Type at default.
   • Result: Created profiles don't work correctly. Components using custom channels must have that channel set as their Object Type.

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Key Points for Custom Collision Usage

Collision profiles and custom collision channels are powerful tools for organizing and efficiently implementing complex collision detection logic in Unreal Engine.

Key Point	Description
Custom Channel	"Tags" for subdividing object types. Two types: Object Type and Trace Channel.
Collision Profile	Presets defining responses (Ignore, Overlap, Block) between channels. Enables centralized management.
Implementation Key	Define necessary channels, create profiles defining responses for those channels, and apply to components. Use Set Collision Profile Name for dynamic changes.

Utilizing these features will give your game a more refined, easier-to-debug collision system.