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;

	}
Apply a 4x4 matrix to the plane. The matrix must be an affine, homogeneous transform.

The optional normal matrix can be pre-computed like so:
```js
const optionalNormalMatrix = new THREE.Matrix3().getNormalMatrix( matrix );
```

@param {Matrix4} matrix - The transformation matrix.
@param {Matrix4} [optionalNormalMatrix] - A pre-computed normal matrix.
@return {Plane} A reference to this plane.