Scene Region Selection¶

Draw a polygon on the Scene View XZ plane, then reuse it in Chat or a spatial_query. Regions are an Editor aid: drawing is disabled while Unity is entering or running Play Mode.

Draw and save a region¶

Focus the Scene View and press Shift+R.
Choose a drawing mode with Q, W, E, or R, or use the MCP Scene overlay.
Draw the shape.
Review the highlighted objects and area in the preview.
Press Enter to save the region, or Escape to discard it.

Key	Mode	Gesture
Q	Lasso	Press and drag a freehand contour; release to preview
W	Rectangle	Press at one corner, drag, and release
E	Circle	Press at the center, drag the radius, and release
R	Point by point	Click vertices; double-click or click near the first vertex to close

Press G to toggle the 0.5-unit grid snap. In point-by-point mode, Escape removes the most recent vertex; use it again at the first vertex to cancel.

The preview highlights up to 50 matching scene objects. Saving creates an eight-character region ID and, when automatic context is enabled, adds a Region chip to MCP Chat.

Query the saved geometry¶

Use the region ID returned by the chip or saved snapshot:

objects = await spatial_query(
    action="objects_in_polygon",
    region_id="a1b2c3d4",
    component="Collider",
    cap=50,
)

component is an optional, case-sensitive component-name substring filter. cap defaults to 50 and is clamped to 200.

You can run the same query without using the Scene View by supplying at least three x,z pairs:

objects = await spatial_query(
    action="objects_in_polygon",
    vertices="0,0;10,0;10,8;0,8",
    cap=50,
)

If both vertices and region_id are supplied, the inline vertices are used and the ID labels the result. See Spatial Tools for other spatial actions.

Use a region in MCP Chat¶

A saved region is represented in the prompt as:

[region:a1b2c3d4]

The resolved context includes its area, bounds, center, object count, scene name, and a bounded list of object paths. Set the chip depth to full when the polygon vertices or the complete stored path list are needed. A STALE marker means the hierarchy changed after the region was captured; query the region again before making decisions from its object list.

The Region chip menu can frame the region, copy stored object paths, or remove the region.

Persistence and limits¶

Regions are stored in Library/MCP_Regions.json, which is local to the Unity project and normally ignored by version control.

At most 20 regions are retained; the oldest is evicted when the limit is exceeded.
Regions survive a domain reload and Editor restart.
Entries older than 24 hours are dropped the next time the store loads.
Geometry uses world XZ coordinates and ignores object height.
Containment tests each GameObject's transform pivot, not its renderer or collider bounds.
The stored object-path snapshot is capped at 50, while a later spatial_query(..., cap=...) can return up to 200 current matches.

Troubleshooting¶

Symptom	What to do
The shortcut does nothing	Focus the Scene View and stop Play Mode
A point-by-point polygon will not preview	Add at least three vertices, then double-click or click near the first vertex
`Region not found`	The entry expired or was evicted; draw and save it again
The chip is marked `STALE`	The hierarchy changed; rerun `spatial_query` before editing objects
A visible object is missing	Its transform pivot may be outside the XZ polygon; use a larger region or an inline polygon
Too few results are returned	Increase `cap` (up to 200) or remove the component filter

For destructive cleanup, use region_clear with its default dry_run=True, review the paths, and only then repeat with dry_run=False.