Components: reading and writing state

The whole write surface

There is no set-position, no set-colour, no set-scale. There is one verb:

entity::set_component(&e, "transform", &[
    ComponentField { path: "translation".into(), value: FieldValue::Vec3(there) },
]).await?;

and its exact inverse, get-component, which echoes back each path you ask for so a read feeds straight into a write.

Capability grows by registering components, never by adding verbs. Today exactly two are registered:

Component	Paths	Notes
transform	translation (vec3), rotation (quat), scale (vec3)	physics-aware, see below
material	base_color (rgba)	applies to every mesh in the subtree

Anything else — visibility, health, mass, light colour — is not writable from a mod. If your design needs one, the change is a row in the host’s whitelist, not a new verb.

transform moves physics bodies too

On a physics body, translation and rotation route to the physics position and rotation rather than the render transform, so a write genuinely moves the thing rather than fighting the simulation for a frame. scale stays on the transform.

This is what makes teleporting work:

let body = entity::body_of(&player).await?;
entity::set_component(&body, "transform", &[
    ComponentField { path: "translation".into(), value: FieldValue::Vec3(spawn) },
]).await?;

A large enough correction is presented as a cut rather than a smooth slide, because sweeping a player across the world is the wrong picture for a deliberate move.

material covers a subtree, and does not bleed

Writing base_color on an entity recolours every mesh beneath it, which is usually what you want for “make this player red”. The archetype’s shared material is cloned on the first write per mesh, so recolouring one instance never tints the others.

Writes replicate

A whitelisted write on a replicated entity reaches every peer over the same path the value took locally, and is folded into what a late joiner receives — so someone arriving after the recolour sees the recoloured thing, not the original.

Root motion is the exception: continuous position and rotation of a replicated root ride the snapshot stream instead, which is what keeps movement smooth.