Actually, you do not have to use a base object to create an effect of the ground under your buildings. Virtual reality applications provides a Ground Color option for the Background helper, which enables you to set the color of the view port below the horizon free 3d max models.
Another option is to hide the faces you do not want instead of deleting them. Because the exporter does not export hidden faces, those faces will not be part of the eventual download file size. MAX still counts the hidden faces, however, and you will not have a completely accurate face count during the modeling process for free 3d max models.
Whether you delete or hide faces is up to you. You may find it more convenient to delete them if your model is intended solely to be viewed in a special browser. You are doubtless already familiar with the optimize modifier; it is hardly necessary to point out its advantages for creating low-face-count models for the virtual worlds.
Perhaps the most useful thing at this point is to look at some examples of objects optimized with this modifier at different levels of severity. Let us see what happens to a 3D mesh with successive increases in the Face Threshold setting.
One 3D max models mesh is not optimized and has 554 faces. The second 3D mesh has the Face Threshold set to 8 and has 538 faces. The third 3D mesh has the Face Threshold set to 12 and has 420 faces. The fourth 3D mesh has the Face Threshold set to 18 and has 342 faces.
From experiments like this, you may conclude that you can turn up the Face Threshold to 12 and still get acceptable results for objects that stay in the middle distance, but that a setting of 18 distorts the mesh too much.
Generally, the more complex the mesh, the more dramatic the savings you get by using the optimize modifier. You need to experiment to find what works best for your scene.