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Use SplitInternalLoops before Polygon is creation (Issue #881) #1043

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Use SplitInternalLoops before Polygon is creation (Issue #881) #1043

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9326630
Use SplitInternalLoops before Polygon is creation.
DmytroMuravskyi Oct 25, 2023
072c583
CHANGELOG.md
DmytroMuravskyi Oct 25, 2023
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1 change: 1 addition & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -57,6 +57,7 @@
- `IndexedPolycurve.GetSubdivisionParameters` now works correctly with `startSetbackDistance` and `endSetbackDistance` parameters.
- `Polyline.Frames` now works correctly with `startSetbackDistance` and `endSetbackDistance` parameters.
- `Polygon.Frames` now works correctly with `startSetbackDistance` and `endSetbackDistance` parameters.
- Fix exception in `Polygon.Difference` and `Profile.Difference` when a inner loop shares edges with outer loop.


### Changed
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179 changes: 18 additions & 161 deletions Elements/src/Geometry/Polygon.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -77,7 +77,7 @@ protected override void ValidateVertices()
}

this.Vertices = Vector3.RemoveSequentialDuplicates(this.Vertices, true);
DeleteVerticesForOverlappingEdges();
Vector3.DeleteVerticesForOverlappingEdges(this.Vertices);
if (this.Vertices.Count < 3)
{
throw new ArgumentException("The polygon could not be created. At least 3 vertices are required.");
Expand Down Expand Up @@ -1494,11 +1494,7 @@ private static IList<Polygon> BooleanTwoSets(IList<Polygon> subjectPolygons, ILi
var polygons = new List<Polygon>();
foreach (List<IntPoint> path in solution)
{
var result = PolygonExtensions.ToPolygon(path, tolerance);
if (result != null)
{
polygons.Add(result);
}
polygons.AddRange(path.ToPolygon(tolerance));
}
return polygons;
}
Expand Down Expand Up @@ -1544,11 +1540,7 @@ public IList<Polygon> Difference(Polygon polygon, double tolerance = Vector3.EPS
var polygons = new List<Polygon>();
foreach (List<IntPoint> path in solution)
{
var result = PolygonExtensions.ToPolygon(path, tolerance);
if (result != null)
{
polygons.Add(result);
}
polygons.AddRange(path.ToPolygon(tolerance));
}
return polygons;
}
Expand Down Expand Up @@ -1583,14 +1575,7 @@ public IList<Polygon> Difference(IList<Polygon> difPolys, double tolerance = Vec
var polygons = new List<Polygon>();
foreach (List<IntPoint> path in solution)
{
try
{
polygons.Add(PolygonExtensions.ToPolygon(path.Distinct().ToList(), tolerance));
}
catch
{
// swallow invalid polygons
}
polygons.AddRange(path.ToPolygon(tolerance));
}
return polygons;
}
Expand Down Expand Up @@ -1620,11 +1605,7 @@ public IList<Polygon> Intersection(Polygon polygon, double tolerance = Vector3.E
var polygons = new List<Polygon>();
foreach (List<IntPoint> path in solution)
{
var result = PolygonExtensions.ToPolygon(path, tolerance);
if (result != null)
{
polygons.Add(result);
}
polygons.AddRange(path.ToPolygon(tolerance));
}
return polygons;
}
Expand All @@ -1651,7 +1632,12 @@ public Polygon Union(Polygon polygon, double tolerance = Vector3.EPSILON)
{
return null;
}
return solution.First().ToPolygon(tolerance);
var polygons = solution.First().ToPolygon(tolerance);
if (polygons.Count > 1)
{
return null;
}
return polygons.First();
}

/// <summary>
Expand Down Expand Up @@ -1694,7 +1680,12 @@ public Polygon Union(IList<Polygon> polygons, double tolerance = Vector3.EPSILON
{
return null;
}
return solution.First().Distinct().ToList().ToPolygon(tolerance);
var results = solution.First().ToPolygon(tolerance);
if (results.Count > 1)
{
return null;
}
return results.First();
}

/// <summary>
Expand All @@ -1718,7 +1709,7 @@ public IList<Polygon> XOR(Polygon polygon, double tolerance = Vector3.EPSILON)
var polygons = new List<Polygon>();
foreach (List<IntPoint> path in solution)
{
polygons.Add(PolygonExtensions.ToPolygon(path, tolerance));
polygons.AddRange(path.ToPolygon(tolerance));
}
return polygons;
}
Expand Down Expand Up @@ -2398,140 +2389,6 @@ protected override Vector3[] NormalsAtVertices()
return result;
}

/// <summary>
/// Deletes Vertices that are out on overloping Edges
/// D__________C
/// | |
/// | |
/// E|_________|B_____A
/// Vertex A will be deleted
/// </summary>
private void DeleteVerticesForOverlappingEdges()
{
if (Vertices.Count < 4)
{
return;
}

for (var i = 0; i < Vertices.Count; i++)
{
var a = Vertices[i];
var b = Vertices[(i + 1) % Vertices.Count];
var c = Vertices[(i + 2) % Vertices.Count];
bool invalid = (a - b).Unitized().Dot((b - c).Unitized()) < (Vector3.EPSILON - 1);
if (invalid)
{
Vertices.Remove(b);
i--;

if (a.IsAlmostEqualTo(c))
{
Vertices.Remove(c);
}
}
}
}

/// <summary>
/// A Polygon can't have self intersections, but points can still lay on other lines.
/// This leads to hidden voids embedded in the perimeter.
/// This function checks if any points are on another line of the loop and splits into distinct loops if found.
/// </summary>
/// <returns>List of simple polygons</returns>
internal List<Polygon> SplitInternalLoops()
{
List<List<Vector3>> polygonPresets = new List<List<Vector3>>();

//Store accumulated vertices and lines between them.
List<Vector3> loopVertices = new List<Vector3>();
List<Line> openLoop = new List<Line>();

//Check if a point lay on active open loop lines.
foreach (var v in Vertices)
{
bool intersectionFound = false;
for (int i = 0; i < openLoop.Count; i++)
{
if (openLoop[i].PointOnLine(v) && v.DistanceTo(openLoop[i]) < Vector3.EPSILON)
{
//Remove points and lines from intersection points to this.
var vertices = loopVertices.Skip(i + 1).ToList();
loopVertices.RemoveRange(i + 1, vertices.Count);
openLoop.RemoveRange(i + 1, vertices.Count - 1);
//Cut intersected line and add this point to open loop.
loopVertices.Add(v);
openLoop[i] = new Line(openLoop[i].Start, v);

//Loop can possibly be just two points connected forth and back.
//Filter it early.
vertices.Add(v);
if (vertices.Count > 2)
{
polygonPresets.Add(vertices);
}
intersectionFound = true;
break;
}
}

//Then check if line (this plus last points) intersects with any accumulated points (going backward)
if (!intersectionFound)
{
Line segment = loopVertices.Any() ? new Line(loopVertices.Last(), v) : null;
for (int i = loopVertices.Count - 1; i >= 0; i--)
{
//Last point is already part of the line.
if (i == loopVertices.Count)
{
continue;
}

if (segment.PointOnLine(loopVertices[i]) && loopVertices[i].DistanceTo(segment) < Vector3.EPSILON)
{
var vertices = loopVertices.Skip(i).ToList();
segment = new Line(loopVertices[i], segment.End);

loopVertices.RemoveRange(i + 1, vertices.Count - 1);
openLoop.RemoveRange(i, vertices.Count - 1);

if (vertices.Count > 2)
{
polygonPresets.Add(vertices);
}
}
}

//If no intersection found just add point and line to open loop.
loopVertices.Add(v);
if (segment != null)
{
openLoop.Add(segment);
}
}
}

//Leftover points form last loop if it has enough points.
if (loopVertices.Count > 2)
{
polygonPresets.Add(loopVertices);
}

List<Polygon> polygons = new List<Polygon>();
foreach (var preset in polygonPresets)
{
try
{
//Polygon constructor cleanup removes any excess vertices and segments.
//This can lead to, again, having too little vertices for valid polygon.
var loop = new Polygon(preset);
polygons.Add(loop);
}
catch
{
//Just ignore polygons that failed check due to having less than 3 points.
}
}
return polygons;
}
}
}
28 changes: 27 additions & 1 deletion Elements/src/Geometry/PolygonExtensions.cs
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Expand Up @@ -34,7 +34,7 @@ internal static List<IntPoint> ToClipperPath(this Polygon p, double tolerance =
/// <param name="p"></param>
/// <param name="tolerance">Optional tolerance value. Be sure to use the same tolerance value as you used when converting to Clipper path.</param>
/// <returns></returns>
internal static Polygon ToPolygon(this List<IntPoint> p, double tolerance = Vector3.EPSILON)
internal static List<Polygon> ToPolygon(this List<IntPoint> p, double tolerance = Vector3.EPSILON)
{
var scale = Math.Round(1.0 / tolerance);
var converted = new Vector3[p.Count];
Expand All @@ -43,6 +43,32 @@ internal static Polygon ToPolygon(this List<IntPoint> p, double tolerance = Vect
var v = p[i];
converted[i] = new Vector3(v.X / scale, v.Y / scale);
}

var polygons = new List<Polygon>();
var cleaned = Vector3.RemoveSequentialDuplicates(converted, true);
Vector3.DeleteVerticesForOverlappingEdges(cleaned);
if (cleaned.Count < 3)
{
return polygons;
}

//Single perimeter can be split not only into one simple perimeter and several voids,
//but also as several independent simple perimeters.
var loops = Vector3.SplitInternalLoops(cleaned);

foreach (var loop in loops)
{
var polygon = ToPolygon(loop);
if (polygon != null)
{
polygons.Add(polygon);
}
}
return polygons;
}

private static Polygon ToPolygon(List<Vector3> converted)
{
try
{
return new Polygon(converted);
Expand Down
8 changes: 4 additions & 4 deletions Elements/src/Geometry/Polyline.cs
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Expand Up @@ -453,12 +453,12 @@ public virtual Polygon[] Offset(double offset, EndType endType, double tolerance
co.AddPath(path, JoinType.jtMiter, clEndType);
co.Execute(ref solution, offset * clipperScale); // important, scale also used here

var result = new Polygon[solution.Count];
for (var i = 0; i < result.Length; i++)
var result = new List<Polygon>();
foreach (List<IntPoint> s in solution)
{
result[i] = solution[i].ToPolygon(tolerance);
result.AddRange(s.ToPolygon(tolerance));
}
return result;
return result.ToArray();
}

/// <summary>
Expand Down
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