void Terrain::Init()
{
  // used to track current entry in the index array

  int index = 0;
  int currentVertex;

  // loop over all vertices in the terrain map

  for (int z = 0; z < MAP_Z; z++)
  {
    for (int x = 0; x < MAP_X; x++)
    {
      // vertices are numbered left to right, top to bottom

      currentVertex = z * MAP_X + x;

      // set the values in the color array

      g_color[currentVertex][0] = g_color[currentVertex][1] =
        g_color[currentVertex][2] = g_terrain[x + MAP_X * z][1]/255.0f;

      // set the values in the texture coordinate array. since the texture

      // is tiled over each "square", we can use texture wrapping

      g_texcoord[currentVertex][0] = (float) x;
      g_texcoord[currentVertex][1] = (float) z;
    }
  }

  for (z = 0; z < MAP_Z - 1; z++)
  {
    for (int x = 0; x < MAP_X; x++)
    {
      currentVertex = z * MAP_X + x;
      g_index[index++] = currentVertex + MAP_X;
      g_index[index++] = currentVertex;
    }
  }

  // enable the vertex arrays being used

  glEnableClientState(GL_VERTEX_ARRAY);
  glEnableClientState(GL_COLOR_ARRAY);
  glEnableClientState(GL_TEXTURE_COORD_ARRAY);

  // pass the pointers to OpenGL

  glVertexPointer(3, GL_FLOAT, 0, g_terrain);
  glColorPointer(3, GL_FLOAT, 0, g_color);
  glTexCoordPointer(2, GL_FLOAT, 0, g_texcoord);
}

void Terrain::Render()
{
  // loop through all the triangle strips

  for (int z = 0; z < MAP_Z-1; z++)
  {
    // draw the triangles in this strip

    glDrawElements(GL_TRIANGLE_STRIP, MAP_X * 2, GL_UNSIGNED_INT, &g_index[z * MAP_X * 2]);
  }
}