API Reference › core-geometry› Curve › RegionOps › ConstructAllXYRegionLoops

constructAllXYRegionLoops MethodStatic

Find all xy-areas bounded by the unstructured, possibly intersecting curves.

  • For best results, input curves should be parallel to the xy-plane, as z-coordinates are ignored.
  • "Holes" implied/bounded by inputs are not preserved/discovered in output; in particular ParityRegion hole loops are treated like any other positive area loops.
  • A common use case of this method is to assemble the bounding negative-area "exterior" loop for each connected component of input curves. Passing addBridges = true decreases the number of connected components for nested input Loops, and thus increases the likelihood of returning exactly one exterior loop. (This is why the default value for addBridges is true.)

constructAllXYRegionLoops(curvesAndRegions: AnyCurve | AnyCurve[], tolerance: number = Geometry.smallMetricDistance, addBridges: boolean = true): SignedLoops[]

@returns array of SignedLoops, each entry of which describes the areas bounded by a single connected component:

  • positiveAreaLoops contains "interior" loops, including holes in ParityRegion input. These loops have positive area and counterclockwise orientation.
  • negativeAreaLoops contains (probably just one) "exterior" loop which is ordered clockwise.
  • slivers contains sliver loops that have zero area, such as appear between coincident curves.
  • edges contains a LoopCurveLoopCurve object for each component edge, collecting both loops adjacent to the edge and a constituent curve in each.
Parameter Type Description
curvesAndRegions AnyCurve | AnyCurve[] Any collection of curves. Each AnyRegion contributes its children stripped of
parity context.
tolerance number optional distance tolerance for coincidence. Default is smallMetricDistance.
addBridges boolean whether to add line segments to connect nested input Loops (default is true). When false,
no line segments are added to the input curves, but the number of output components may be greater than expected.

Returns - SignedLoops[]

array of SignedLoops, each entry of which describes the areas bounded by a single connected component:

  • positiveAreaLoops contains "interior" loops, including holes in ParityRegion input. These loops have positive area and counterclockwise orientation.
  • negativeAreaLoops contains (probably just one) "exterior" loop which is ordered clockwise.
  • slivers contains sliver loops that have zero area, such as appear between coincident curves.
  • edges contains a LoopCurveLoopCurve object for each component edge, collecting both loops adjacent to the edge and a constituent curve in each.

Defined in

Last Updated: 29 October, 2025