rig.spatial.anchor

Which cell of an entity's local bounds is the local origin. Format when present. Axes stay +X +Y +Z - the host offsets to the named cell; it does not invert signs.

Not a locator you place - that is rig.spatial.vertex. Not rig.font.anchor (named glyph point).

XY (point):

Together with height, that is a 3×3×3 cuboid cell (27 corners / edge midpoints / centre) without twenty-seven string ids.

Absent component: do not remap. Local (0,0) stays where the entity's size schema already puts it - page trim defaults to top-left; rig.geometry.rectangle keeps its authored x,y corner; centre-authored primitives (ellipse, regular_polygon, star, arc, ring) keep their authored centerX/centerY.

When present: point (and optional height) names which cell of the local axis-aligned bounds coincides with local (0,0,0) (and with rig.spatial.transform position when that is present). Then add offset. The host offsets from authored bounds to honour it - geometry field layouts do not change. Interior directions follow the host axes: an origin at top-left on a Y-up bed means the interior is +X and −Y.

Compose onto any entity that has local bounds. On a page, it is also where page-local (0,0) sits for children. height matters when the host has a Z extent (machine envelope, mesh AABB, 3D zone); planar pages may omit it. Z free-pivot (offsetZ / vec3) is not in this draft.

Do not put this enum or offset on transform - pose stays TRS only. Do not re-declare the field on rig.layout.page or geometry schemas. Do not encode origin as axis invert (signX / signY / signZ). Do not treat point and offset as alternatives - snap to the cell, then nudge.

Bounds come from the entity's size (page trim, rectangle extent, ellipse radii, host AABB for meshes). Without bounds, omit this component.

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://rig.works/schemas/rig.spatial.anchor.schema.json",
  "title": "rig.spatial.anchor",
  "type": "object",
  "additionalProperties": false,
  "properties": {
    "point": {
      "type": "string",
      "enum": [
        "top-left",
        "top-center",
        "top-right",
        "middle-left",
        "center",
        "middle-right",
        "bottom-left",
        "bottom-center",
        "bottom-right"
      ]
    },
    "height": {
      "type": "string",
      "enum": [
        "min",
        "center",
        "max"
      ]
    },
    "offset": {
      "$ref": "./_defs.schema.json#/$defs/vec2"
    }
  },
  "required": [
    "point"
  ]
}