Face

Face

Class representing a face (closed loop) in a polygon object. Face is a circular bidirectional linked list of edges. Face object cannot be instantiated with a constructor. Instead, use polygon.addFace() method.
Note, that face only set entry point to the linked list of edges but does not contain edges by itself. Container of edges is a property of the polygon object.

Constructor

new Face()

Source:
Example
// Face implements "next" iterator which enables to iterate edges in for loop:
for (let edge of face) {
     console.log(edge.shape.length)     // do something
}

// Instead, it is possible to iterate edges as linked list, starting from face.first:
let edge = face.first;
do {
  console.log(edge.shape.length);   // do something
  edge = edge.next;
} while (edge != face.first)

Classes

Face

Members

_box

Reference to the last edge in face
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box

Return bounding box of the face
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edges

Return array of edges from first to last
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perimeter

Get all edges length
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shapes

Return array of shapes which comprise face
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Methods

append(edge) → {Face}

Append edge after the last edge of the face (and before the first edge).
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Parameters:
Name Type Description
edge Edge Edge to be appended to the linked list
Returns:
Type:
Face

area() → {number}

Returns the absolute value of the area of the face
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Returns:
Type:
number

findEdgeByPoint(pt) → {Edge}

Returns edge which contains given point
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Parameters:
Name Type Description
pt Point test point
Returns:
Type:
Edge

insert(newEdge, edgeBefore) → {Face}

Insert edge newEdge into the linked list after the edge edgeBefore
Source:
Parameters:
Name Type Description
newEdge Edge Edge to be inserted into linked list
edgeBefore Edge Edge to insert newEdge after it
Returns:
Type:
Face

isSimple(edges) → {boolean}

Returns true if face of the polygon is simple (no self-intersection points found) NOTE: this method is incomplete because it does not exclude touching points. Self intersection test should check if polygon change orientation in the test point.
Source:
Parameters:
Name Type Description
edges PlanarSet reference to polygon edges to provide search index
Returns:
Type:
boolean

merge_with_next_edge(edge) → {Face}

Merge current edge with the next edge. Given edge will be extended, next edge after it will be removed. The distortion of the polygon is on the responsibility of the user of this method
Source:
Parameters:
Name Type Description
edge Edge edge to be extended
Returns:
Type:
Face

orientation() → {number}

Return face orientation: one of Flatten.ORIENTATION.CCW, Flatten.ORIENTATION.CW, Flatten.ORIENTATION.NOT_ORIENTABLE
According to Green theorem the area of a closed curve may be calculated as double integral, and the sign of the integral will be defined by the direction of the curve. When the integral ("signed area") will be negative, direction is counterclockwise, when positive - clockwise and when it is zero, polygon is not orientable. See https://mathinsight.org/greens_theorem_find_area
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Returns:
Type:
number

pointAtLength(length) → {Point}

Get point on face boundary at given length
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Parameters:
Name Type Description
length number The length along the face boundary
Returns:
Type:
Point

remove(edge) → {Face}

Remove the given edge from the linked list of the face
Source:
Parameters:
Name Type Description
edge Edge Edge to be removed
Returns:
Type:
Face

reverse()

Reverse orientation of the face: first edge become last and vice a verse, all edges starts and ends swapped, direction of arcs inverted. If face was oriented clockwise, it becomes counterclockwise and vice versa
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setArcLength()

Set arc_length property for each of the edges in the face. Arc_length of the edge it the arc length from the first edge of the face
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signedArea() → {number}

Returns signed area of the simple face. Face is simple if it has no self intersections that change its orientation. Then the area will be positive if the orientation of the face is clockwise, and negative if orientation is counterclockwise. It may be zero if polygon is degenerated.
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Returns:
Type:
number

svg() → {string}

Returns string to be assigned to "d" attribute inside defined "path"
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Returns:
Type:
string

toPolygon() → {Polygon}

Returns new polygon created from one face
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Returns:
Type:
Polygon