Download a mesh data structure and read in some mesh to display. If there are quad faces in the mesh, you should draw each quad as two triangles. To draw with "flat shading", compute a single normal for each face, and use it for drawing. Next, compute one "average normal" for each vertex. An average-normal at a vertex will be the average of the normals of all the faces around the vertex. Draw the mesh with "smooth shading", using this average-normal when drawing each vertex.