Skip to content

Latest commit

 

History

History
214 lines (145 loc) · 6.26 KB

polygon.md

File metadata and controls

214 lines (145 loc) · 6.26 KB
Raw

Polygon

A polygon consists of a convex shape with any number of points (specified in a counter-clockwise order).

property type description default
position Vector A vector representing the origin of the polygon (all other points are relative to this one). vector(0, 0)
points Array An array of vectors representing the points of the polygon, in counter-clockwise order. 0

example:

const polygon = new Polygon(new Vector(0, 0), [
  new Vector(0, 0),
  new Vector(40, 0),
  new Vector(40, 40),
  new Vector(0, 40)
]);

Getters

position

Returns the position of the polygon.

points

Returns the points of the polygon.

calcPoints

Returns an array of vectors of the calculated points of the polygon.

offset

Returns a vector representing the offset of the polygon.

angle

Returns the angle of the polygon, in radians.

edges

Returns an array of vectors representing the edges of the polygon.

normals

Returns an array of vectors representing the normals of the polygon.

Methods

setPoints

Set the points of the polygon. Any consecutive duplicate points will be combined.

Note: The points are counter-clockwise with respect to the coordinate system. If you directly draw the points on a screen that has the origin at the top-left corner it will appear visually that the points are being specified clockwise. This is just because of the inversion of the Y-axis when being displayed.

This is called automatically when a polygon is initialized.

property type description default
points Array An array of vectors representing the points of the polygon, in counter-clockwise order.

example:

const polygon = new Polygon(new Vector(0, 0), [
  new Vector(0, 0),
  new Vector(40, 0),
  new Vector(40, 40),
  new Vector(0, 40)
]);

polygon.setPoints([
  new Vector(0, 0),
  new Vector(80, 0),
  new Vector(80, 80),
  new Vector(0, 80)
);

setAngle

Sets the current rotation angle of the polygon.

property type description default
angle number The current rotation angle, in radians.

example:

const polygon = new Polygon(new Vector(0, 0), [
  new Vector(0, 0),
  new Vector(40, 0),
  new Vector(40, 40),
  new Vector(0, 40)
]);

polygon.setAngle(45);

setOffset

et the current offset to apply to the points before applying the angle rotation.

property type description default
offset Vector The vector representing the offset

example:

const polygon = new Polygon(new Vector(0, 0), [
  new Vector(0, 0),
  new Vector(40, 0),
  new Vector(40, 40),
  new Vector(0, 40)
]);

polygon.setOffset(new Vector(2, 5));

rotate

Rotates this Polygon counter-clockwise around the origin of its local coordinate system (i.e. position)

Note: This changes the original points (so any angle will be applied on top of this rotation).

property type description default
angle number The rangle to rotate, in radians

example:

const polygon = new Polygon(new Vector(0, 0), [
  new Vector(0, 0),
  new Vector(40, 0),
  new Vector(40, 40),
  new Vector(0, 40)
]);

polygon.rotate(45);

translate

Translates the points of this polygon by a specified amount relative to the origin of its own coordinate system (i.e. position).

Note: This changes the original points (so any offset will be applied on top of this translation)

property type description default
x number The horizontal amount to translate.
y number The vertical amount to translate.

example:

const polygon = new Polygon(new Vector(0, 0), [
  new Vector(0, 0),
  new Vector(40, 0),
  new Vector(40, 40),
  new Vector(0, 40)
]);

polygon.translate(5, 10);

getAABB

Compute the axis-aligned bounding box.

Any current state (translations/rotations) will be applied before constructing the AABB.

Note: Returns a new Polygon each time you call this.

example:

const polygon = new Polygon(new Vector(0, 0), [
  new Vector(0, 0),
  new Vector(40, 0),
  new Vector(40, 40),
  new Vector(0, 40)
]);

const polygonBoundingBox = polygon.getAABB();

getCentroid

Compute the centroid (geometric center) of the Polygon.

Any current state (translations/rotations) will be applied before computing the centroid.

See https://en.wikipedia.org/wiki/Centroid#Centroid_of_a_polygon

Note: Returns a new Vector each time you call this.

example:

const polygon = new Polygon(new Vector(0, 0), [
  new Vector(0, 0),
  new Vector(40, 0),
  new Vector(40, 40),
  new Vector(0, 40)
]);

const centroid = polygon.getCentroid();