Learning > geometry > Region Ops
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Examples of RegionOps

RegionOps.splitPathsByRegionInOnOutXY

This splits any curve into parts in, on, and outside an xy region.

25 points >
split the black path into parts inside and outside the grey area const splitParts = RegionOps.splitPathsByRegionInOnOutXY(path, loop);
(red) Path parts "inside" the region
splitParts.insideParts		 >
(green) Path parts "outside" the region
splitParts.outsideParts		 >

Remarks

Using a closed region as the cutter is a specialized high level operation, just one of the many ways that splitting may be needed. It is a combination of

a split step uses the region boundary curves but not the interior/exterior properties. const splitPaths = RegionOps.splitToPathsBetweenFlagBreaks ((pathWithIntersectionMarkup, true);
a classification step tests one point from each fragment of the splitPaths:
(a) obtain one point on a fragment being tested const pointOnChild = CurveCollection.createCurveLocationDetailOnAnyCurvePrimiitive(splitPaths);
(b) determine if that single point is inside or outside.
since the fragments have no interior crossings, that point classifies the whole fragment		 const inOnOut = RegionOps.testPointInOnOutRegionXY(region, pointOnChild.point.x, pointOnChild.point.y);

Unit Test

  • source: core\geometry\src\test\topology\RegionOps.test.ts
  • test name: "InOutSplits"
  • output: core\geometry\src\test\output\RegionOps\InOutSplits.imjs

RegionOps.testPointInOnOutRegionXY

This tests whether single points are in, out, or on an xy region.

Parity region with various test points
circle is "on"
diamond is "in"
plus is "out"		 >

Unit Test

  • source: core\geometry\src\test\topology\RegionOps.test.ts
  • test name: "MixedInOut"
  • output: core\geometry\src\test\output\RegionOps\MixedInOut.imjs

RegionOps.regionBooleanXY

Compute union, intersection, and difference among area regions.

The call form is RegionOps.regionBooleanXY(regionA, regionB, opcode) where

  • Each of regionA and regionB may be
    • a single Loop
    • a single ParityRegion
    • an array of Loop and ParityRegion
      • all the loops and parity regions within each array are considered as a union.
  • The operation between regionA and regionB is one of
    • RegionBinaryOpType.Union
    • RegionBinaryOpType.Intersection
    • RegionBinaryOpType.AMinusB
    • RegionBinaryOpType.BMinusA

For a first example, each of regionA and regionB is a single Loop:

filletedRectangle = CurveFactory.createRectangleXY(0, 0, 5, 4, 0, 1); >
splitter = CurveFactory.createRectangleXY(1, -1, 6, 2); >
Both regions, placed for operations >
union = RegionOps.regionBooleanXY(filletedRectangle, splitter, RegionBinaryOpType.Union); >
intersection = RegionOps.regionBooleanXY(filletedRectangle, splitter, RegionBinaryOpType.Intersection); >
diff = RegionOps.regionBooleanXY(filletedRectangle, splitter, RegionBinaryOpType.AMinusB); >

For a second example, each of regionA and regionB is an array of regions to be treated as a union:

  • region A is constructed by

    const manyRoundedRectangles = [];
for (let a = 0; a < 5; a += 1) {
  manyRoundedRectangles.push(CurveFactory.createRectangleXY(a, a, a + 4, a + 1.75, 0, 0.5));
}

    and region B by

      const splitterB0 = CurveFactory.createRectangleXY(0.5, 0.4, 6, 2.1, 0, 0);
  const splitterB1 = splitterB0.cloneTransformed(Transform.createFixedPointAndMatrix({ x: 1, y: 2, z: 0 }, Matrix3d.createRotationAroundAxisIndex(2, Angle.createDegrees(40)))) as Loop;
  const splitterB = [splitterB0, splitterB1];
region A >
region B >
Both regions, placed for operations >
unionB = RegionOps.regionBooleanXY(manyRoundedRectangles, splitterB, RegionBinaryOpType.Union); >
intersectionB = RegionOps.regionBooleanXY(manyRoundedRectangles, splitterB, RegionBinaryOpType.Intersection); >
diffB = RegionOps.regionBooleanXY(manyRoundedRectangles, splitterB, RegionBinaryOpType.AMinusB); >

Unit Test

  • source: core\geometry\src\test\topology\RegionBoolean.test.ts
  • test name: "DocDemo"
  • output: core\geometry\src\test\output\sweepBooleans\DocDemo.imjs

Last Updated: 02 February, 2022