   spot light question
  I am not sure how to do this, but I need a way to have a spotlight shine on a cube. I only want it to light up a little bit of the cube. I have tried but my attempts have ended up either lighting the whole cube or none of it.I am going to make the spotlight be movable with keyboard.  
  Lighting calculations are pretty much per-vertex.  This means that you must have many vertices for a spotlight to look good.  Each face of the cube must be represented by a large number of triangles.  If you don''t want to subdivide the faces, lightmapping may be an option for you.  You can use a texture map for luminosity so parts of the cube end up looking darker than others. 