title: Setting the indices for a 3d mesh in libGDX
body: <p>i got stuck with a problem in libGDX. I want to create a simple untextured 3d model out of a mesh. This is my code so far to create a tetrahedron:</p>
  
  <pre><code>Material material = new Material(new IntAttribute(IntAttribute.CullFace), ColorAttribute.createDiffuse(Color.GRAY));
  ModelBuilder modelBuilder = new ModelBuilder();
  Mesh mesh = new Mesh(true, 6, 20, new VertexAttribute(Usage.Position, 3, "test"));
  mesh.setVertices(new float[] { -0.5f, -0.5f, 0,
                                  0.5f, -0.5f, 0,
                                  0, 0.5f, 0,
                                  0, 0, 1});
  
  mesh.setIndices(new short[] {0, 3, 0, 2, 0, 1, 1, 3, 1, 2, 2, 3});
  modelBuilder.begin();
  modelBuilder.part("test", mesh, GL20.GL_LINE_STRIP, material);
  model = modelBuilder.end();
  </code></pre>
  
  <p>This code works fine but i don't know how to set the mesh's indices for generated vertices.
  I currently got a list with Vertices and each Vertex got a list which contains the Vertices with it is connected. 
  How i have to set the mesh's indices to realize this connections?</p>
  
  <p>Thanks in advance and sorry for my bad english. </p>