_addVertexToHull( eyeVertex ) {

		const horizon = [];

		this.unassigned.clear();

		// remove 'eyeVertex' from 'eyeVertex.face' so that it can't be added to the 'unassigned' vertex list

		this._removeVertexFromFace( eyeVertex, eyeVertex.face );

		this._computeHorizon( eyeVertex.point, null, eyeVertex.face, horizon );

		this._addNewFaces( eyeVertex, horizon );

		// reassign 'unassigned' vertices to the new faces

		this._resolveUnassignedPoints( this.newFaces );

		return	this;

	}
Adds a vertex to the hull with the following algorithm:

- Compute the 'horizon' which is a chain of half edges. For an edge to belong to this group
it must be the edge connecting a face that can see 'eyeVertex' and a face which cannot see 'eyeVertex'.
- All the faces that can see 'eyeVertex' have its visible vertices removed from the assigned vertex list.
- A new set of faces is created with each edge of the 'horizon' and 'eyeVertex'. Each face is connected
with the opposite horizon face and the face on the left/right.
- The vertices removed from all the visible faces are assigned to the new faces if possible.

@private
@param {VertexNode} eyeVertex - The vertex to add.
@return {ConvexHull} A reference to this convex hull.