The intersection of the two bezier is empty

[ArtOfOmission]

var tt1 = new Bezier(20.294698715209961, 20.116849899291992,
 26.718513488769531, 28.516490936279297,
 33.345268249511719, 37.4105110168457,
 36.240531921386719,37.736736297607422);
var tt2 = new Bezier(43.967803955078125, 30.767040252685547,
43.967803955078125, 31.771089553833008,
35.013500213623047, 32.585041046142578,
23.967803955078125, 32.585041046142578);
var ttList = tt1.intersects(tt2);

The two bezier curves should intersect, but the result returned is empty，
Two bezier curves are marked with red lines in the figure

[Pomax]

You're not logging ttList in your console log instruction. You're logging an undefined variable tList. I can highly recommend installing a JS linting extension, or switching your theme, to make sure that undeclared variables are "obviously" highlighted as "this code has a problem even if it'll still run".

[justvanrossum]

I tried earlier, and the snippet (once the tList/ttList typo is fixed) indeed shows an empty result list, despite that the input curves indeed do visually intersect.

[ArtOfOmission]

thanks for the replay，ttList is alse empty.

[ArtOfOmission]

I tried earlier, and the snippet (once the tList/ttList typo is fixed) indeed shows an empty result list, despite that the input curves indeed do visually intersect.

I updated the code

[ArtOfOmission]

You're not logging ttList in your console log instruction. You're logging an undefined variable tList. I can highly recommend installing a JS linting extension, or switching your theme, to make sure that undeclared variables are "obviously" highlighted as "this code has a problem even if it'll still run".

I updated the code. The variable name is wrong, but the ttList is alse empty.

[Pomax]

console logging investigation:

    console.log
      running

      at Bezier.intersects (src/bezier.js:848:13)

    console.log
      curveintersects args:

      at Bezier.curveintersects (src/bezier.js:886:13)

    console.log
      c1 [
        Bezier {
          _3d: false,
          points: [ [Object], [Object], [Object], [Object] ],
          order: 3,
          dims: [ 'x', 'y' ],
          dimlen: 2,
          _linear: true,
          _lut: [],
          _t1: 0,
          _t2: 0.05158051653718898,
          dpoints: [ [Array], [Array], [Array] ],
          clockwise: false
        },
        Bezier {
          _3d: false,
          points: [ [Object], [Object], [Object], [Object] ],
          order: 3,
          dims: [ 'x', 'y' ],
          dimlen: 2,
          _linear: true,
          _lut: [],
          _t1: 0.05158051653718898,
          _t2: 0.05455413371263488,
          dpoints: [ [Array], [Array], [Array] ],
          clockwise: false
        }
      ]

      at Bezier.curveintersects (src/bezier.js:887:13)

    console.log
      c2 [
        Bezier {
          _3d: false,
          points: [ [Object], [Object], [Object], [Object] ],
          order: 3,
          dims: [ 'x', 'y' ],
          dimlen: 2,
          _linear: false,
          _lut: [],
          _t1: 0,
          _t2: 0.09,
          dpoints: [ [Array], [Array], [Array] ],
          clockwise: false
        },
        Bezier {
          _3d: false,
          points: [ [Object], [Object], [Object], [Object] ],
          order: 3,
          dims: [ 'x', 'y' ],
          dimlen: 2,
          _linear: false,
          _lut: [],
          _t1: 0.09,
          _t2: 1,
          dpoints: [ [Array], [Array], [Array] ],
          clockwise: false
        }
      ]

      at Bezier.curveintersects (src/bezier.js:888:13)

    console.log
      initial pairs []

      at Bezier.curveintersects (src/bezier.js:898:13)

    console.log
      intersections []

      at Bezier.curveintersects (src/bezier.js:913:13)

  ● Intersection testing › https://github.com/Pomax/bezierjs/issues/203

[Pomax]

Looks like the this.reduce() call in intersects yields a curve set that does not span the full [0,1] interval.

[Pomax]

   console.log
      running

      at Bezier.intersects (src/bezier.js:859:13)

    console.log
      first pass reductions: [
        Bezier {
          _3d: false,
          points: [ [Object], [Object], [Object], [Object] ],
          order: 3,
          dims: [ 'x', 'y' ],
          dimlen: 2,
          _linear: true,
          _lut: [],
          _t1: 0,
          _t2: 0.05158051653718898,
          dpoints: [ [Array], [Array], [Array] ],
          clockwise: false
        },
        Bezier {
          _3d: false,
          points: [ [Object], [Object], [Object], [Object] ],
          order: 3,
          dims: [ 'x', 'y' ],
          dimlen: 2,
          _linear: true,
          _lut: [],
          _t1: 0.05158051653718898,
          _t2: 0.05455413371263488,
          dpoints: [ [Array], [Array], [Array] ],
          clockwise: false
        },
        Bezier {
          _3d: false,
          points: [ [Object], [Object], [Object], [Object] ],
          order: 3,
          dims: [ 'x', 'y' ],
          dimlen: 2,
          _linear: false,
          _lut: [],
          _t1: 0.05455413371263488,
          _t2: 1,
          dpoints: [ [Array], [Array], [Array] ],
          clockwise: true
        }
      ]

      at Bezier.reduce (src/bezier.js:601:13)

    console.log
      second pass on: Bezier {
        _3d: false,
        points: [
          { x: 20.29469871520996, y: 20.116849899291992 },
          { x: 20.62604239936939, y: 20.550107722706766 },
          { x: 20.95792601544804, y: 20.98468086613082 },
          { x: 21.289809631526694, y: 21.419325704546704 }
        ],
        order: 3,
        dims: [ 'x', 'y' ],
        dimlen: 2,
        _linear: true,
        _lut: [],
        _t1: 0,
        _t2: 0.05158051653718898,
        dpoints: [
          [ [Object], [Object], [Object] ],
          [ [Object], [Object] ],
          [ [Object] ]
        ],
        clockwise: false
      }

      at forEach (src/bezier.js:605:15)
          at Array.forEach (<anonymous>)

    console.log
      t1: 0, t2: 1.0100000000000007

      at forEach (src/bezier.js:629:15)
          at Array.forEach (<anonymous>)

    console.log
      second pass on: Bezier {
        _3d: false,
        points: [
          { x: 21.289809631526694, y: 21.419325704546704 },
          { x: 21.308942724548533, y: 21.44438298282736 },
          { x: 21.328075817570372, y: 21.469440499388 },
          { x: 21.347208807140635, y: 21.49449801594864 }
        ],
        order: 3,
        dims: [ 'x', 'y' ],
        dimlen: 2,
        _linear: true,
        _lut: [],
        _t1: 0.05158051653718898,
        _t2: 0.05455413371263488,
        dpoints: [
          [ [Object], [Object], [Object] ],
          [ [Object], [Object] ],
          [ [Object] ]
        ],
        clockwise: false
      }

      at forEach (src/bezier.js:605:15)
          at Array.forEach (<anonymous>)

    console.log
      t1: 0, t2: 1.0100000000000007

      at forEach (src/bezier.js:629:15)
          at Array.forEach (<anonymous>)

    console.log
      second pass on: Bezier {
        _3d: false,
        points: [
          { x: 21.347208807140635, y: 21.494498015948643 },
          { x: 27.430441729082755, y: 29.46140298519073 },
          { x: 33.50321685100052, y: 37.42830795443282 },
          { x: 36.24053192138672, y: 37.73673629760742 }
        ],
        order: 3,
        dims: [ 'x', 'y' ],
        dimlen: 2,
        _linear: false,
        _lut: [],
        _t1: 0.05455413371263488,
        _t2: 1,
        dpoints: [
          [ [Object], [Object], [Object] ],
          [ [Object], [Object] ],
          [ [Object] ]
        ],
        clockwise: true
      }

      at forEach (src/bezier.js:605:15)
          at Array.forEach (<anonymous>)

[Pomax]

    console.log
      second pass on: Bezier {
        _3d: false,
        points: [
          { x: 21.347208807140635, y: 21.494498015948643 },
          { x: 27.430441729082755, y: 29.46140298519073 },
          { x: 33.50321685100052, y: 37.42830795443282 },
          { x: 36.24053192138672, y: 37.73673629760742 }
        ],
        order: 3,
        dims: [ 'x', 'y' ],
        dimlen: 2,
        _linear: false,
        _lut: [],
        _t1: 0.05455413371263488,
        _t2: 1,
        dpoints: [
          [ [Object], [Object], [Object] ],
          [ [Object], [Object] ],
          [ [Object] ]
        ],
        clockwise: true
      }

      at forEach (src/bezier.js:605:15)
          at Array.forEach (<anonymous>)

    console.log
      dead segment for t1:0 and t2:0

Looks like the second pass in the reduction function needs some proper debugging.