First-person item configs

Motion uses a data-driven first-person item presentation system for local first-person items.

Each item is described by a UMotionFirstPersonItemConfig asset. The asset tells Motion which actor to spawn for local first-person presentation, which linked animation layer to use, which socket to attach to, and which relative transform to apply.

The built-in pistol uses this system through DA_FPItem_Pistol.

What a first-person item config is

A first-person item config is a UPrimaryDataAsset that defines the content-side setup for one local first-person item presentation.

The asset owns the compact set of fields that runtime code consumes:

• PresentationActorClass: actor spawned for local first-person presentation.
• LinkedLayerClass: item or stance layer linked while the item is active.
• PresentationAttachSocket: socket used for the presentation actor.
• PresentationRelativeTransform: local framing transform applied after attach.

This keeps per-item presentation in content while keeping Motion's shared first-person body logic in Motion-owned code and linked layers.

Runtime flow

At runtime, UMotionHeldItemComponent treats the active item config as the local first-person item definition for the held item path.

Animation layer responsibilities

Motion uses two item-related linked layers for the current first-person path:

• FullBody_FirstPersonItemItemSpace: item-specific helper-space or item-space adjustments.
• FullBody_FirstPersonItemUpperBody: shared Motion-owned upper-body pitch and solve behavior.

The main AnimGraph path in ABP_Mannequin_Base evaluates item space before upper body.

Built-in pistol asset

DA_FPItem_Pistol is the default first-person pistol config. It points to:

• PresentationActorClass: BP_Pistol
• LinkedLayerClass: ABP_PistolAnimLayers
• PresentationAttachSocket: weapon_r
• PresentationRelativeTransform: baseline pistol transform

B_MotionCharacter uses this through the MotionHeldItem component's DefaultDebugItemConfig.

Current scope

This system is scoped to local first-person presentation only. It does not own:

• remote third-person item presentation
• inventory semantics
• gameplay equip state
• muzzle logic
• hand target metadata
• generic item role resolution

Those systems can be layered on top of Motion's presentation contract.

Current limitations

• The config drives presentation class, linked layer, socket, and transform only.
• Live PIE tuning uses an explicit save step.
• PIE verification depends on a clean PIE session.
• New reflected editor buttons and properties may require an editor restart if they were added through Live Coding.

Practical recommendation

Use this system as the content-facing boundary for item presentation, not as a full weapon framework.

Keep item-specific attach/framing in the config asset, item-specific item-space graph logic in FullBody_FirstPersonItemItemSpace, and shared body/aim behavior in FullBody_FirstPersonItemUpperBody.

For setup steps, see How to create a first-person item config.