Arc: fix interactions negative domain in GetSubdivisionParameters, Complement and ToPolyline.

[DmytroMuravskyi]

BACKGROUND:

• While working on Arc I realized that I can't call ToPolyon for the arc that has StartAngle > EndAngle. Result had only one point.

DESCRIPTION:

• Arc.GetSubdivisionParameters: returns parameters starting from StartAngle even if StartAngle > EndAngle.EndAngle.
• Arc,ToPolyline: now works if StartAngle > EndAngle.EndAngle.
• Arc.Complement: now works if StartAngle > EndAngle.EndAngle or if both angles are negative.

TESTING:

• Tests are added for each change

FUTURE WORK:

• There is discussion about the solution in https://github.com/hypar-io/Elements/issues/994

REQUIRED:

• [x] All changes are up to date in CHANGELOG.md.

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This change is 

[andrewheumann]

I think this solution is the wrong approach — it leave's a curve's tangent vector in disagreement with its parameter space.

var arc1 = new Arc(transform, 2, 0, Math.PI / 2.0);
var arc2 = new Arc(transform, 2, Math.PI / 2.0, 0);
Assert.Equal(arc1.PointAtNormalized(0.2), arc2.PointAtNormalized(0.8));
Assert.True(arc1.TransformAtNormalized(0.2).ZAxis.Dot(arc2.TransformAtNormalized(0.8).ZAxis) < -0.9999);

This will fail with this change.

I have implemented the earlier proposed approach here, which satisfies this expectation. https://github.com/hypar-io/Elements/pull/999

[DmytroMuravskyi]

Few details I noticed about your implementation that might be by design or already known:

• Direction in TransformAt is opposite from Arc direction (may be by design):

          var arc = new Arc(Vector3.Origin, 5.0, 0.0, 180.0);
          var t = arc.TransformAt(Math.PI / 2);
          Assert.Equal(new Vector3(0, 1, 0), t.XAxis);
          Assert.Equal(new Vector3(0, 0, 1), t.YAxis);
          Assert.Equal(new Vector3(1, 0, 0), t.ZAxis);

• Literals with this approach will produce values affected by transformation (users should be well aware of this behavior and understand that numbers they see in Domain are not the final one they are getting) :

          var arc = new Arc(Vector3.Origin, 5.0, 180, 45);
          var t = arc.TransformAt(Math.PI / 2); //X = -0.707106781186, Y = 0.70710678118654, Z = 1.22464679914735E-16
          var p = arc,PointAt(Math.PI / 2); //X = -3.5355339059327373, Y = 3.5355339059327386, Z = 6.1232339957367663E-16

  Few changes that can be copied from this PR into new simplified one:

• GetSubdivisionParameters doesn't follow parametrization.

          var arc = new Arc(Vector3.Origin, 2.0, 0.0, -90.0);
          var parameters = arc.GetSubdivisionParameters();
          Assert.Equal(0, parameters.First()); //Fails and returns -PI/2

• Complement for negative arc returns more negative arc. arc = new Arc(Vector3.Origin, 1, -40, -80); comp = arc.Complement(); Assert.Equal(-40, comp.StartAngle); // returns -400 Assert.Equal(280, comp.EndAngle); //returns -80

[wynged]

@andrewheumann want to make sure you see these comments from Dmytro above.