> I have been trying to find out how the history works.

It gets applied automatically when you edit objects that were input into a command.

For example - draw a curve then do a revolve to make a lathed type shape from the curve.

Now select the original curve, turn on points for it and drag some of the points around to change the shape of the curve. You will see the lathed surface (the result of the Revolve command) update as you edit the generator curve - the update of the lathed surface is construction history in action.

Some commands generate objects that have history updates turned on by default - these are Extrude, Blend, Revolve, Loft, Sweep, Offset, Planar. Other commands still generate history but by default the update is turned off, this is because for some basic workhorse type commands such as copy, it can sometimes get in your way if history updates are going on when all you want to do is manipulate objects individually.

You can turn on or off history updates for a particular object by selecting it and using Edit/History.

So for example if you don't want the revolve to update when you edit its generator curve, you can select the revolved surface and do Edit/History and turn updates off - now the revolve will not update when you edit its input curve.

Similarly you can turn on history updates for the results of other commands if you wish, for example the result of a mirror can have history updates turned on so that it gets updated when its original half is edited. I use this in this recent mini tutorial: http://moi3d.com/forum/index.php?webtag=MOI&msg=402.9 - that goes through the steps to set up a lofted surface where you can edit some curves for half of a surface but see the full mirrored object update as you edit.

Let me know if you have any questions about any particular aspect of history.

- Michael