OFFSET

Another element moved sideways by a distance: a parallel copy that follows it.

Syntax

OFFSET @source,distance
OFFSET @id,@source,distance,layer
OFFSET @id,@source,distance,layer,CORNERS="MITRE"

Argument	Meaning
@source	The element to offset.
distance	How far: positive to the left of the source's direction, negative to the right. An expression, usually a variable.
CORNERS	How its corners are joined where it opens away from the source: `"ROUND"` (the default), `"MITRE"` or `"SQUARE"`.

The id, layer and any settings after it are the element settings. Without a layer, the offset goes on the current layer; the Offset Tool writes each offset's layer, by default its source's.

Examples

BEZIER @1,P0,P3,P2,P1
GAP=10
OFFSET @2,@1,GAP
OFFSET @3,@1,-GAP

OFFSET example

P10=[0,0]
P11=[100,0]
P12=[50,150]
POLYLINE @4,[P10,P11,P12],TRUE
SA=10
OFFSET @5,@4,-SA,0,CORNERS="MITRE"
OFFSET @6,@4,-2*SA,0,CORNERS="SQUARE"

A seam allowance round a triangle (drawn anticlockwise, so its outside is to the right: a negative distance), its corners mitred; and one twice as far out, its corners squared off.

Notes

The offset is worked out from the source whenever the source or the distance changes. Lines and arcs offset exactly, other curves within a small tolerance; a closed source gives a closed offset.

Where the offset opens away from its source at a corner, the corner is rounded (the exact offset), unless CORNERS says otherwise: CORNERS="MITRE" carries the two sides on until they meet in a point, and CORNERS="SQUARE" carries them on no further than the distance and cuts across between them (a mitre where they meet within that: at corners of 90° or more). The Seam Allowance Tool writes them.