Actor-Free Placement

Development docs. This page describes the unreleased 6.3 build.

Not every placement needs a character. A level editor, a city builder's grid, a room-stacking demo, or a sandbox with no inventory can place objects with nothing bound to placer_root. In 6.3 that is a supported state, not a misconfiguration: session.get_placer_root() returns null and placement works.

The rule is simple: a placer is required exactly when an enabled rule says it is. PlacementRule.requires_placer() returns false by default; rules that read the acting node for range, inventory or spending answer true — for example SpendMaterialsRuleById.

Ask the session, do not guess

var requirement:StringName = session.placer_requirement()
# "" -> this session places fine with no actor
# "spend_materials" -> that enabled rule cannot run without one

placer_requirement() resolves through the same tiers the validator runs, so a rule the profile ignores never demands a placer.

What each state does

State	Behavior
No placer, no enabled rule needs one	commits normally; reports name no placer
No placer, an enabled rule needs one	the commit lane refuses with a typed reason and mutates nothing
Placer bound, rule needs it	the rule runs against that node

The refusal is shared by the single-press and drag-release lanes so both describe the gap the same way:

No placer assigned and rule 'spend_materials' requires one. Assign the
positioner's placer_root or call PlacementSession.set_placer_root().

Setup health

Editor setup health reports an unbound placer as optional, with the reason that it is needed only when an enabled rule requires a player. PlacementOwner warnings and a missing-placer runtime issue appear only when the configuration actually demands an actor, so an actor-free scene does not start with a warning it cannot act on.

Choosing

• No actor-dependent rules? Bind nothing. Delete the placer assignment and the 6.2 PlacementOwner node if you still have one.
• Range, inventory or cost rules? Bind a placer, and expect a typed refusal rather than a silent placement whenever it is missing or freed.

Do not invent a dummy player node to satisfy the old requirement: nothing in 6.3 reads a placer that no enabled rule asked for.