added some support functions

	return &i, nil

}

func calculateMidPoint(va Vertex, vb Vertex, r float64) (Vertex, error) {

	var vr Vertex

	var vt Vertex

func (v Vertex) add(a Vertex) Vertex {

	var r Vertex

	r.x = v.x + a.x

	r.y = v.y + a.y

	r.z = v.z + a.z

	return r

}

func (v Vertex) sub(a Vertex) Vertex {

	var r Vertex

	r.x = v.x - a.x

	r.y = v.y - a.y

	r.z = v.z - a.z

	return r

}

	vt.x = vb.x - va.x

	vt.y = vb.y - va.y

	vt.z = vb.z - va.z

func (v Vertex) scale(s float64) Vertex {

	var r Vertex

	r.x = v.x * s

	r.y = v.y * s

	r.z = v.z * s

	return r

}

	vr.x = va.x + (vt.x * r)

	vr.y = va.y + (vt.y * r)

	vr.z = va.z + (vt.z * r)

func calculateMidPoint(va Vertex, vb Vertex, r float64) (Vertex, error) {

	vr := va.add(vb.sub(va).scale(r))

	return vr, nil

}