OK, this is a very common option whenever you are crating a copy of some feature, usually when doing a Copy & Paste' (this is why I asked the question that I did). The idea is that when creating actual COPIES of a feature and not meerly instances, that we give you the option of creating individual expressions for each copy, that the first option 'Create New', which allows you 100% freedom to come in afterwards and edit any expression of any of the copies and give them whatever value that you wish/ The second option, 'Link to Original' is similar in that every copy will get it's own expressions, just that they will all be set to be equal the name of the expressions used for the original 'parent' feature. That way, if you edit an expression of the 'parent', all of the 'children' will update as well, but you could have gone in and overwritten the expression giving it its own value and not the original's p-number. Now the last option 'Reuse Original' creates NO new expressions whatsoever, it simply uses the SAME expression for all copies meaning that while if you edit the 'parent' expressions the 'children' still update, just that you have NO options for going into a single copy and changing the expressions of just that single copy.
Now this only applies if you use the 'Variational' Pattern Method and you've used the 'Copy Features' output option. If you had used the default which is 'Pattern Feature' you won't get those options since this will create a TRUE pattern where all the 'copies' are instances of the 'parent' period. Now the same is true if you had used the 'Simple' Pattern Method, and here you have no options whatsoever but to get true instances.
Now if you really wanted to edit one or more the copies created using Pattern Feature there is no real need to even use the 'Copy Features' scheme because even if you create true instances, you can still go in and select a single instance and going into Edit Parameters and you will be given teh option to override the values, nit by editing an expression, but by editing the feature directly to make an exception as it were. This will work whether you used the 'Simple' or 'Variational' method.
Now if you ask why we include this 'Copy Features' option using duplicate expressions, this is there IF you really need to control the parameters of the copies using expressions and you don't want to have to create an exception for each expression of each instance that you want to have access to since you have to do that even GET and expression that can override the parent's parameter inheritied by the children.
Now my advise of to ALWAYS use the 'Simple' Method unless you get a message stating that you need to use Variational (some situations require it). And don't worry about encountering this during an edit of any existing Pattern because stating with NX 8.5 you now edit the pattern switching it from 'Simple' to 'Variational' if you need to. The biggest reason to ALWAYS use 'Simple' is that you get about 90% of the capabilities for about 90% of the situations and you edit with a model which will update MUCH faster and it will take up less disk space when saved. So I would always start out assuming that can use 'Simple' and just keep working that way until you run into one of those 10% cases and worry about it then.
Anyway, I hope this helps.
Note that starting with NX 9.0 we've added some additional 'Pattern' options such as Pattern Geometry and Pattern Faces, which could be even more efficient if you don't need as much control over individual copies in the Pattern. I know this may sound confusing at first but after awhile you'll learn the pro's and con's and then you can get model with update faster and which open and save faster as well, so all of this is done so that the user gets the best of everything, eitehr more flexibility or higher performance or more simplicity. Your choice, not ours.
John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
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