I havent edited in awhile but I seem to remember having serious troubles with 3dos, or any dynamic object for that matter when placed behind textures flagged as sky. ( it was visable through the texture even though it was behind the texture) What exactly are we looking at back there? It looks like a large sprite of some type., which would be consistant with the problems I had. Are there other objects behind the sky? Or is the rest all all archi? Try testing things out, placing various types of objects behind a sky texture (walkplayers, weapons, projectiles, dynamic lights, standard 3dos, etc) and see what happens.