>>One of those rules used to be NOT to use instances because they make the model very heavy. Am I wrong here ? Have I been fooled all those years ?! ;-) Instances take actually less memory ?<< Hi Pim, Yes, Instances and References take up less memory than copies and give you the flexibility of easy edits. >>Or could there be a reason why you wouldn't want a lot of instances (I'm talking hundreds of instances here)<< I'm not sure if there would be a situation where the overhead of keeping track of the instances would outweigh the savings of the node space. I suppose if you had hundreds of cloned objects with complex modifier stacks there's overhead, but I can't imagine it would be more efficient if the objects were copies. The modifiers don't have "nodes" so there is minimum memory advantage of having them clones (but there is a big flexibility advantage) >>will max' raytracer have less problems with a thousend instances<< Only if it become a memory issue. The Raytracer uses a fair amount of memory, so instance would free some. The Raytracer doesn't differentiate clones to my knowledge, though. >>Or never to use groups<< I personally never use groups, but there are cases where they are useful if you know the potential problems. Groups are a special form of hierarchical linking and when you use scaled object (that's a NEVER) in a group and then animate it there will be problems that are difficult to track. I have a client in the oil industry who is constantly having trouble with animations because of scaled objects in groups imported from CAD. Easy to fix when you recognize the issue, but a bear otherwise, and easy to avoid in the first place. >>Are there any pointers/ articles that explain how max works ?<< I don't know of any compendium of knowledge of the workings of max, but I'd love to see it, too. These are tidbits of information that I've picked up from working around Autodesk employees over the years, mostly over beers after hours. :) >>Hope I'm not bothering you too much<< Not at all, Pim, your input is valuable and these sorts of discussions can point out little things that are important. You're working kind of late, though! :) Later Ted