ent_morph is also decent, provided all LOD entities are preloaded into memory. Ent_morph is better in some ways (such as the fact you don't have to set the positions of each LOD entity one by one in the script). If not preloaded into memory, it'll read from the hard drive and it could otherwise cause a slow down. Ent_morph, in general, if used properly, is better than simply turning the invisible flag on and off. With 1728 invisible entities, the rendering time is 0.2 milliseconds, virtually nothing. The experiment, however, didn't include calculating visibility with vec_dist for each object, but since that formula is relatively simple, that shouldn't cause a major slow down. You don't have to do it with each individual object, rather you only need to do it with one of the objects.