Table of Contents

Class YuPengClipper

Namespace
Alis.Core.Physic.Common.PolygonManipulation
Assembly
Alis.dll

The yu peng clipper class

public static class YuPengClipper

Inheritance

Inherited Members

Fields

ClipperEpsilonSquared

The clipper epsilon squared

private const float ClipperEpsilonSquared = 1.1920929E-07

Field Value

float

Methods

BuildPolygonsFromChain(List<Edge>, out List<Vertices>)

Calculates the polygon(s) from the result simplical chain.

private static PolyClipError BuildPolygonsFromChain(List<YuPengClipper.Edge> simplicies, out List<Vertices> result)

Parameters

simplicies List<YuPengClipper.Edge>
result List<Vertices>

Returns

PolyClipError

Remarks

Used by method Execute().

CalculateBeta(Vector2, Edge, float)

Needed to calculate the characteristics function of a simplex.

private static float CalculateBeta(Vector2 point, YuPengClipper.Edge e, float coefficient)

Parameters

point Vector2
e YuPengClipper.Edge
coefficient float

Returns

float

Remarks

Used by method CalculateEdgeCharacter().

CalculateIntersections(Vertices, Vertices, out Vertices, out Vertices)

Calculates all intersections between two polygons.

private static void CalculateIntersections(Vertices polygon1, Vertices polygon2, out Vertices slicedPoly1, out Vertices slicedPoly2)

Parameters

polygon1 Vertices

The first polygon.

polygon2 Vertices

The second polygon.

slicedPoly1 Vertices

Returns the first polygon with added intersection points.

slicedPoly2 Vertices

Returns the second polygon with added intersection points.

CalculateResultChain(List<float>, List<Edge>, List<float>, List<Edge>, PolyClipType, out List<Edge>)

Calculates the characteristics function for all edges of the given simplical chains and builds the result chain.

private static void CalculateResultChain(List<float> poly1Coeff, List<YuPengClipper.Edge> poly1Simplicies, List<float> poly2Coeff, List<YuPengClipper.Edge> poly2Simplicies, PolyClipType clipType, out List<YuPengClipper.Edge> resultSimplices)

Parameters

poly1Coeff List<float>
poly1Simplicies List<YuPengClipper.Edge>
poly2Coeff List<float>
poly2Simplicies List<YuPengClipper.Edge>
clipType PolyClipType
resultSimplices List<YuPengClipper.Edge>

Remarks

Used by method Execute().

CalculateSimplexCoefficient(Vector2, Vector2, Vector2)

Returns the coefficient of a simplex.

private static float CalculateSimplexCoefficient(Vector2 a, Vector2 b, Vector2 c)

Parameters

a Vector2
b Vector2
c Vector2

Returns

float

Remarks

Used by method CalculateSimplicalChain().

CalculateSimplicalChain(Vertices, out List<float>, out List<Edge>)

Calculates the simplical chain corresponding to the input polygon.

private static void CalculateSimplicalChain(Vertices poly, out List<float> coeff, out List<YuPengClipper.Edge> simplicies)

Parameters

poly Vertices
coeff List<float>
simplicies List<YuPengClipper.Edge>

Remarks

Used by method Execute().

Difference(Vertices, Vertices, out PolyClipError)

Differences the polygon 1

public static List<Vertices> Difference(Vertices polygon1, Vertices polygon2, out PolyClipError error)

Parameters

polygon1 Vertices

The polygon

polygon2 Vertices

The polygon

error PolyClipError

The error

Returns

List<Vertices>

A list of vertices

Execute(Vertices, Vertices, PolyClipType, out PolyClipError)

Implements "A new algorithm for Boolean operations on general polygons" available here: http://liama.ia.ac.cn/wiki/_media/user:dong:dong_cg_05.pdf Merges two polygons, a subject and a clip with the specified operation. Polygons may not be self-intersecting. Warning: May yield incorrect results or even crash if polygons contain collinear points.

private static List<Vertices> Execute(Vertices subject, Vertices clip, PolyClipType clipType, out PolyClipError error)

Parameters

subject Vertices

The subject polygon.

clip Vertices

The clip polygon, which is added, substracted or intersected with the subject

clipType PolyClipType

The operation to be performed. Either Union, Difference or Intersection.

error PolyClipError

The error generated (if any)

Returns

List<Vertices>

A list of closed polygons, which make up the result of the clipping operation. Outer contours are ordered counter clockwise, holes are ordered clockwise.

GetAlpha(Vector2, Vector2, Vector2)

Needed for sorting multiple intersections points on the same edge.

private static float GetAlpha(Vector2 start, Vector2 end, Vector2 point)

Parameters

start Vector2
end Vector2
point Vector2

Returns

float

Remarks

Used by method CalculateIntersections().

Intersect(Vertices, Vertices, out PolyClipError)

Intersects the polygon 1

public static List<Vertices> Intersect(Vertices polygon1, Vertices polygon2, out PolyClipError error)

Parameters

polygon1 Vertices

The polygon

polygon2 Vertices

The polygon

error PolyClipError

The error

Returns

List<Vertices>

A list of vertices

PointInSimplex(Vector2, Edge)

Winding number test for a point in a simplex.

private static bool PointInSimplex(Vector2 point, YuPengClipper.Edge edge)

Parameters

point Vector2

The point to be tested.

edge YuPengClipper.Edge

The edge that the point is tested against.

Returns

bool

False if the winding number is even and the point is outside the simplex and True otherwise.

PointOnLineSegment(Vector2, Vector2, Vector2)

Tests if a point lies on a line segment.

private static bool PointOnLineSegment(Vector2 start, Vector2 end, Vector2 point)

Parameters

start Vector2
end Vector2
point Vector2

Returns

bool

Remarks

Used by method CalculateBeta().

Union(Vertices, Vertices, out PolyClipError)

Unions the polygon 1

public static List<Vertices> Union(Vertices polygon1, Vertices polygon2, out PolyClipError error)

Parameters

polygon1 Vertices

The polygon

polygon2 Vertices

The polygon

error PolyClipError

The error

Returns

List<Vertices>

A list of vertices

VectorEqual(Vector2, Vector2)

Describes whether vector equal

private static bool VectorEqual(Vector2 vec1, Vector2 vec2)

Parameters

vec1 Vector2

The vec

vec2 Vector2

The vec

Returns

bool

The bool