code: public void createQuad(float width, float height)
      {
          String vertexDescriptor = getVertexBuffer().getDescriptor();
          float[] vertices = { width * -0.5f, height * 0.5f, 0.0f, width * -0.5f,
                  height * -0.5f, 0.0f, width * 0.5f, height * 0.5f, 0.0f,
                  width * 0.5f, height * -0.5f, 0.0f };
          setVertices(vertices);
  
          if (vertexDescriptor.contains("normal"))
          {
              final float[] normals = {0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f};
              setNormals(normals);
          }
  
          if (vertexDescriptor.contains("texcoord"))
          {
              final float[] texCoords = {0.0f, 0.0f, 0.0f, 1.0f, 1.0f, 0.0f, 1.0f, 1.0f};
              setTexCoords(texCoords);
          }
  
          char[] triangles = { 0, 1, 2, 1, 3, 2 };
          setIndices(triangles);
      }
docs: Sets the contents of this mesh to be a quad consisting of two triangles,
  with the specified width and height. If the mesh descriptor allows for
  normals and/or texture coordinates, they are added.
  
  @param width
  the quad's width
  @param height
  the quad's height