public static Segment3?CropBy(this Segment3 @this, Plane plane)
{
var signedDist = @this.Start.SignedDistanceTo(plane);
var t = -signedDist / (plane.Normal * @this.Vector);
if (t > 0 && t < 1) // plane intersects @this
{
if (signedDist > 0)
{
return(new Segment3(@this.PointAt(t), @this.End));
}
else
{
return(new Segment3(@this.Start, @this.PointAt(t)));
}
}
else // plane doesn't intersect @this
{
if (signedDist > 0)
{
return(null);
}
else
{
return(@this);
}
}
}
public void Cropping_Segment3_by_plane_produces_null_when_entire_segment_is_on_negative_side()
{
var segment = new Segment3(new Vector3(3.14, 2.88, -1.77), new Vector3(0.52, -5.08, 1.23));
var point = segment.PointAt(1.256);
var plane = new Plane(point, normal: new Vector3(0.66, 1.44, -0.87));
var crop = segment.CropBy(plane);
Expect(crop == null);
}
public void Cropping_Segment3_by_plane_produces_original_segment_when_entire_segment_is_on_positive_side()
{
var segment = new Segment3(new Vector3(3.14, 2.88, -1.77), new Vector3(0.52, -5.08, 1.23));
var point = segment.PointAt(-0.256);
var plane = new Plane(point, normal: new Vector3(0.66, 1.44, -0.87));
var crop = segment.CropBy(plane);
Expect(crop != null);
Expect(Vector3.Distance(crop.Value.Start, segment.Start), Is.LessThan(_tolerance));
Expect(Vector3.Distance(crop.Value.End, segment.End), Is.LessThan(_tolerance));
}