Plane.js

import { Matrix3 } from './Matrix3.js';
import { Vector3 } from './Vector3.js';

const _vector1 = /*@__PURE__*/ new Vector3();
const _vector2 = /*@__PURE__*/ new Vector3();
const _normalMatrix = /*@__PURE__*/ new Matrix3();

class Plane {

	constructor( normal = new Vector3( 1, 0, 0 ), constant = 0 ) {

		// normal is assumed to be normalized

		this.normal = normal;
		this.constant = constant;

	}

	set( normal, constant ) {

		this.normal.copy( normal );
		this.constant = constant;

		return this;

	}

	setComponents( x, y, z, w ) {

		this.normal.set( x, y, z );
		this.constant = w;

		return this;

	}

	setFromNormalAndCoplanarPoint( normal, point ) {

		this.normal.copy( normal );
		this.constant = - point.dot( this.normal );

		return this;

	}

	setFromCoplanarPoints( a, b, c ) {

		const normal = _vector1.subVectors( c, b ).cross( _vector2.subVectors( a, b ) ).normalize();

		// Q: should an error be thrown if normal is zero (e.g. degenerate plane)?

		this.setFromNormalAndCoplanarPoint( normal, a );

		return this;

	}

	copy( plane ) {

		this.normal.copy( plane.normal );
		this.constant = plane.constant;

		return this;

	}

	normalize() {

		// Note: will lead to a divide by zero if the plane is invalid.

		const inverseNormalLength = 1.0 / this.normal.length();
		this.normal.multiplyScalar( inverseNormalLength );
		this.constant *= inverseNormalLength;

		return this;

	}

	negate() {

		this.constant *= - 1;
		this.normal.negate();

		return this;

	}

	distanceToPoint( point ) {

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

	}

	distanceToSphere( sphere ) {

		return this.distanceToPoint( sphere.center ) - sphere.radius;

	}

	projectPoint( point, target ) {

		return target.copy( this.normal ).multiplyScalar( - this.distanceToPoint( point ) ).add( point );

	}

	intersectLine( line, target ) {

		const direction = line.delta( _vector1 );

		const denominator = this.normal.dot( direction );

		if ( denominator === 0 ) {

			// line is coplanar, return origin
			if ( this.distanceToPoint( line.start ) === 0 ) {

				return target.copy( line.start );

			}

			// Unsure if this is the correct method to handle this case.
			return null;

		}

		const t = - ( line.start.dot( this.normal ) + this.constant ) / denominator;

		if ( t < 0 || t > 1 ) {

			return null;

		}

		return target.copy( direction ).multiplyScalar( t ).add( line.start );

	}

	intersectsLine( line ) {

		// Note: this tests if a line intersects the plane, not whether it (or its end-points) are coplanar with it.

		const startSign = this.distanceToPoint( line.start );
		const endSign = this.distanceToPoint( line.end );

		return ( startSign < 0 && endSign > 0 ) || ( endSign < 0 && startSign > 0 );

	}

	intersectsBox( box ) {

		return box.intersectsPlane( this );

	}

	intersectsSphere( sphere ) {

		return sphere.intersectsPlane( this );

	}

	coplanarPoint( target ) {

		return target.copy( this.normal ).multiplyScalar( - this.constant );

	}

	applyMatrix4( matrix, optionalNormalMatrix ) {

		const normalMatrix = optionalNormalMatrix || _normalMatrix.getNormalMatrix( matrix );

		const referencePoint = this.coplanarPoint( _vector1 ).applyMatrix4( matrix );

		const normal = this.normal.applyMatrix3( normalMatrix ).normalize();

		this.constant = - referencePoint.dot( normal );

		return this;

	}

	translate( offset ) {

		this.constant -= offset.dot( this.normal );

		return this;

	}

	equals( plane ) {

		return plane.normal.equals( this.normal ) && ( plane.constant === this.constant );

	}

	clone() {

		return new this.constructor().copy( this );

	}

}

Plane.prototype.isPlane = true;

export { Plane };