Agent Skills: Weapon Trail

Weapon Trail

Create a ribbon trail effect that follows a weapon's movement.

Technique

Build a custom BufferGeometry that stores a history of positions in a ring buffer. Each frame, record the current world positions of trail points and update the geometry vertices to create a ribbon connecting all historical positions.

Key Concepts

• Define trail points (e.g., base and tip of weapon)
• Use a ring buffer to store position history efficiently
• Create geometry with proper UVs for texture mapping (gradient fade)
• Update vertex positions each frame with positions.needsUpdate = true
• Use localToWorld() to get world positions from the target object
• Support enabling/disabling with fade out animation

Usage

const trailPoints = [new Vector3(0, 0, 0), new Vector3(0, 1.5, 0)]

<group ref={weaponRef}>
  <mesh>{/* weapon mesh */}</mesh>
</group>
<Trail target={weaponRef} points={trailPoints} enabled={isAttacking} />

Geometry Structure

• Segments: historical snapshots (oldest to newest)
• Points per segment: trail point positions at that time
• UVs: u = position along trail (0-1), v = age (0 = newest, 1 = oldest)
• Alpha map texture for gradient fade effect

This skill is part of verekia's r3f-gamedev.