title: libgdx point light not working on generated mesh
body: <p>I've been trying to illuminate plane meshes generated by the following:</p>
  
  <pre><code>private Model createPlane(float w, float h, Texture texture) {
     Mesh mesh = new Mesh(true, 4, 6, new VertexAttribute(Usage.Position, 3, "a_position"),
             new VertexAttribute(Usage.TextureCoordinates, 2, "a_texCoord0"),
             new VertexAttribute(Usage.Normal, 3, "a_normal")); 
  
     float w2 = w * this.CELL_SIZE;
     float h2 = h * this.CELL_SIZE;
  
      mesh.setVertices(new float[]
              { w2, 0f, h2, 0, 0, 0, 1, 0,
              w2, 0f, -h2, 0, h, 0, 1, 0,
              -w2, 0f, h2, w, 0, 0, 1, 0,
              -w2, 0f, -h2 , w,h, 0, 1, 0
              });
      mesh.setIndices(new short[] { 0, 1, 2, 1, 3, 2});
      Model model = ModelBuilder.createFromMesh(mesh, GL10.GL_TRIANGLES, new Material(TextureAttribute.createDiffuse(texture)));
      return model;
  }
  </code></pre>
  
  <p>and are rendered using:</p>
  
  <pre><code>//the environment setup
  env = new Environment();
          env.set(new ColorAttribute(ColorAttribute.AmbientLight, 0.4f, 0.4f, 0.4f, 1f));
          env.add(new PointLight().set(Color.ORANGE, 5f, 1f, 5f, 10f));
          env.add(new DirectionalLight().set(Color.WHITE, -1f, -0.8f, -0.2f));
  ...
  //the render method
  batch.begin();
  batch.render(inst, env);//inst is a ModelInstance created using the Model generated from createPlane(...)
  batch.end();
  </code></pre>
  
  <p>The meshes display correctly (UVs, textured) and seem to be properly affected by directional and ambient lighting.</p>
  
  <p>When I try to add a point light (see above environment) none of the planes generated from createPlane(...) are affected. I've tried creating another bit of geometry using the ModelBuilder class's createBox(...) and it seems to properly respond to the point light. Because of that I'm assuming that I'm not generating the plane correctly, but the fact that it's apparently being affected by directional/ambient light is throwing me off a bit.</p>
  
  <p>It's worth noting that the size of the planes generated vary, I'm not particularly sure if a point light would affect 4 vertices very much but I expected more than nothing. Moving the point light around (closer to certain vertices) doesn't do anything either.</p>
  
  <p>Any help would be greatly appreciated.</p>
  
  <p>Thanks!</p>