Assembly Along the Spline

import { Steps } from ‘@astrojs/starlight/components’;

Assembly along the spline is an optional effect where a multi-part mesh starts as scattered, exploded pieces and assembles itself as it travels the path. It’s entirely opt-in. With assembly off, the deformation is bit-for-bit the normal flow.

Setting it up has two halves: baking pieces (splitting the mesh) on the Pieces tab, then tuning the assembly on the Behavior tab.

1. Bake the pieces

The Pieces tab splits one mesh into rigid chunks. Open it from the tab strip, or from a Bake Pieces… button (on the component’s hero card or the Behavior tab’s Assembly section).

1. Pick a split mode for how the mesh breaks into pieces:

   Split mode	How it splits
   Connected Faces	Into separate connected shells (the natural choice for a mesh of distinct parts).
   Materials	One piece per material slot.
   Lattice	A grid shatter, the always-works fallback that chops any mesh into chunks.
   Vertex Dissolve	A finer per-vertex break-up.

2. The Pieces tab takes over the viewport preview. Use the in-tab Play / Stop toggle to check the split:

   • Stopped → Segmentation: each piece is tinted a distinct color so you can confirm the mesh actually split. A welded mesh that collapses to a single piece is flagged here; switch split modes if you see that.
   • Playing → Assemble: the looping explode → settle, driven by the Assembly controls.

3. Click Commit to write a durable pieces mesh and bind it to the actor.

Static meshes only

Piece baking works on Static Meshes. The committed pieces asset is written under /Game/SplineJuiceGenerated and the bind is undoable. Leaving the tab or closing the panel before committing restores the mesh exactly; everything before Commit is transient.

Bake a whole group at once

With multiple actors selected, one Commit bakes every selected actor’s mesh (the button reads Commit Bake (N actors)), each split with the tab’s current settings. Actors already baked, or without a static mesh, are skipped.

2. Tune the assembly

Once pieces are committed, the Behavior tab’s Assembly section swaps from the Bake Pieces… button to the real controls:

Control	What it does
Enable Assembly	Turns the effect on. Off = pure flow deformation.
Assemble Curve	The eased global sweep that resolves pieces over the journey.
Explode Radius	How far pieces scatter while unresolved.
Tumble Turns	How much each piece spins while exploded.
Assemble Window	The fraction of the journey a single piece takes to snap into place.
Assemble Lag	Staggers pieces in time by index (0 = a purely spatial assembly front).

Assembly needs a bake first

If you enable Assembly but a selected mesh has no committed pieces, Generate warns and jumps you to the Pieces tab; it never silently picks a default split. The deform materials still generate; assembly simply stays off for that mesh until you bake and commit pieces for it.

How it fits together

• The Pieces tab owns the pieces asset: baking, previewing, and committing.
• The Behavior tab owns the assembly tuning.
• The settings panel’s Recreate action only rebuilds the material variants; it never touches your committed pieces.

Each Meshes & Materials card shows a Pieces baked ✓ / No piece bake indicator so you can see at a glance which meshes are assembly-ready.