The barycentric coordinate λ_j at a point is determined by first constructing a sub-tetrahedron (the translucent gray region) composed of the point of interest and all the vertices except the jth vertex. The volume of this sub-tetrahedron is then divided by the total tetrahedral volume formed by the four vertices. Notice that as the point of interest moves closer to the jth vertex, then λ_j approaches one, and as the point moves further away λ_j approaches zero.