three.js/src/math/convexhull/Face.js

import { HalfEdge } from './HalfEdge';
import { Vector3 } from '../Vector3';
import { Triangle } from '../Triangle';
import { Visible, Deleted } from '../../constants';

/**
 * @author Mugen87 / https://github.com/Mugen87
 *
 */

function Face() {

	this.normal = new Vector3();
	this.midpoint = new Vector3();
	this.area = 0;

	this.constant = 0; // signed distance from face to the origin
	this.outside = null; // reference to a vertex in a vertex list this face can see
	this.mark = Visible;
	this.edge = null;

}

Object.assign( Face, {

	create: function( a, b, c ) {

		var face = new Face();

		var e0 = new HalfEdge( a, face );
		var e1 = new HalfEdge( b, face );
		var e2 = new HalfEdge( c, face );

		// join edges

		e0.next = e2.prev = e1;
		e1.next = e0.prev = e2;
		e2.next = e1.prev = e0;

		// main half edge reference

		face.edge = e0;

		return face.compute();

	}

} );

Object.assign( Face.prototype, {

	getEdge: function ( i ) {

		var edge = this.edge;

		while ( i > 0 ) {

			edge = edge.next;
			i --;

		}

		while ( i < 0 ) {

			edge = edge.prev;
			i ++;

		}

		return edge;

	},

	compute: function () {

		var triangle;

		return function compute () {

			if ( triangle === undefined ) triangle = new Triangle();

			var a = this.edge.tail();
			var b = this.edge.head();
			var c = this.edge.next.head();

			triangle.set( a.point, b.point, c.point );

			triangle.normal( this.normal );
			triangle.midpoint( this.midpoint );
			this.area = triangle.area();

			this.constant = this.normal.dot( this.midpoint );

			return this;

		};

	}(),

	distanceToPoint: function ( point ) {

		return this.normal.dot( point ) - this.constant;

	}

} );


export { Face };