You cant open object sequences as yet but you could use one of the many render managers to render a sequence of terragen files each with a different model in it. All you would need to do is load the model once save the terragen file and open it in a text editor. Then simple change as resave the object marker in each file so tg_anim_001.tgd has model_001.obj and tg_anim_002.tgd has model_002.obj and so on. Take about five min to set up.
richard
