Hierarchy node confusion

[Scott Ayers]

Absolute reference, and use start position are ways to target a specific object in the OM. And with using that comes some restrictions. Where relative allows you to be less tied down to a specific object.
The help files do a pretty good job of explaining it. But it is a little bit confusing.
So I'll try explaining it using a coffee tag vs.coffee node instead. Because it's easier to visually see the difference between them.


If you create a coffee tag and use the code: doc->FindObject("Cube") in it. The code will only work on that specific Cube object.
If you make a copy of the Cube. That tag won't work on the copy, so you'll need to edit the code to also point to your copy.
This is an example of an absolute reference.

However.

If you create a coffee node inside of xpresso. And put that same code in it.
You'll be able to make as many copies of the Cube, and that code will still work on all the copies without needing to edit it.
This is because the xpresso coffee node is using a relative type of reference.

It's very rare that you'll need to use an absolute mode for anything. And in fact, it can be dangerous because if you get into the middle of a project and then want to make copies of things. You'll have to edit them all by hand. As opposed to being free to paste as many copies as you want with reference mode without needing to do any extra work on them.

Hope that made sense.

-ScottA

[mark render]

hi scott,
thank you for your detailed explanation. two more questions:
1. you say "If you make a copy of the Cube. That tag won't work on the copy". what if the copy of the cube has a different name ("Cube 2") than the original ("Cube")? it still won´t work because it´s relative to the object carrying the tag, isn´t it? correct?

2. in general, when "Relative Reference" mode is used, what is the "Reference Path" linkfield for then?
i mean, if i set it to "Relative Reference", and have the referring object defined in the "Reference"-Linkfield, isn´t this one automatically my Reference Path?
Or, in other words, what is the difference between "Reference" (the linkfiled above, on top) and "Reference Path"

the help only says:
"Edit the Path using the Box."

[Srek]

Relative Reference will start the iteration at a point relative to the position of the XPresso tag. The link field will change accordingly.
Check the screenshots, they only differ in the reference path. D (Down) will make the iteration start from the cone instead of the cylinder.
Cheers
Björn

[mark render]

Hi Srek,
ok, that makes things clear, thanks.
BUT:
when i change the reference path by hand (for example type in D in your case) the reference itself in the linkfield changes accordingly anyway (see your attachment), so one can say that "Reference Path" and "Reference" IS THE SAME. Isn´t it?

[Srek]

Where do you see Relative as an own option?
You only got:
Use Start position (uses the object that holds the Xpresso tag to start the iteration)
Absolute (uses the linked object to start the iteration)
Relative Reference (uses the object determined by object that holds the Xpresso tag + the reference path. The resulting object will be displayed in the reference. If you change this link by hand the node will switch to absolute reference)

[mark render]

Hi Björn,
i never talked about seeing Relative as an own option... :)
Anyway, your description is as simple as perfect, now it´s clear.
your four lines are much clearer than the description in the help menu ...

cheers

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