Mesh:setVertexMap
Sets the vertex map for the Mesh. The vertex map describes the order in which the vertices are used when the Mesh is drawn. The vertices, vertex map, and mesh draw mode work together to determine what exactly is displayed on the screen.

The vertex map allows you to re-order or reuse vertices when drawing without changing the actual vertex parameters or duplicating vertices. It is especially useful when combined with different Mesh Draw Modes.
Mesh:setVertexMap( map )
map table A table containing a list of vertex indices to use when drawing. Values must be in the range of Mesh:getVertexCount().
Mesh:setVertexMap( vi1, vi2, vi3 )
vi1 number The index of the first vertex to use when drawing. Must be in the range of Mesh:getVertexCount().
vi2 number The index of the second vertex to use when drawing.
vi3 number The index of the third vertex to use when drawing.
Mesh:setVertexMap( data, datatype )
data Data Array of vertex indices to use when drawing. Values must be in the range of Mesh:getVertexCount()-1
datatype IndexDataType Datatype of the vertex indices array above.