What are the data blocks vs. objects?

I’m quickly learning how to use Blender (227) and am doing well so far. One thing I’m not clear on is the difference/meaning of the internal data blocks.

Let’s say I need 20 traffic cones in a scene. I make the basic cone model, texture it and what not, and it’s done. What’s the difference between Shift-D and Alt-D (I think those are the two duplication commands), and if I modify the original model, what happens to the copies? What if I modify a copy, does that change all copies too? Another way to ask this is, if I need to rotate a particular cone instance, how does doing an object rotation versus an edit-mode rotation affect the original/copied cones?

The other day the object-mode (non-edit) scaling versus edit-mode scaling bit me. It’s a very important difference, especially with lofted curves…

thanks

Shift-D creates real copies. That is, it creates a new Object data AND copies the mesh data. The copies are not linked together, so if you edit one (in edit mode), the other doesn’t change.

Alt-D creates linked copies. That is, it creates a new Object data AND link the same Mesh data to it. The copies are linked together, so any changes you make in Edit mode will be carried on to the other copies as well.

hope that is clear enough.

Martin

Thanks for the explanation, that did it.