Sets the index buffer for the submesh.
A submesh is simply a separate indices array. When the mesh renderer uses multiple materials, you should ensure that there are as many submeshes as materials.
SetTriangles and ::triangles always make the mesh be composed of triangles faces. Using SetIndices you can create a mesh that's made out of lines or points, see MeshTopology enum.
See Also: subMeshCount, MeshTopology enum.