Orienting relative to an already oriented object.

I have an application where I'd like to generate a sequence of objects based off of a text file containing a sequence of numbers. I would have a file containing the numbers 1-4 in some order, and from that it would generate a sequence containing one of four elements in the same order as the file, each object oriented relative to the object before it.

That is, say I have a list '1214321'. What I'd like grasshopper to do is take a copy of object 2 and orient its front face with the back face of a copy of object 1. Then I'd like the script to take another copy of object 1 and orient its front face with the back face of the copy of object 2. I'd like to continue this until the program runs out of items in the list.

I know how to read files, but I don't know if reading a list sequentially, or if conditionals, for that matter, are possible. Is this the right way of going about it? Is there a more "grasshopper" way of doing this?

Thanks

P.S. here is a screenshot of something I did by hand, which I'd like to automate. you can see one of the objects I'd like to orient here (it's the highlighted one).

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Permalink Reply by Andrew Heumann on February 15, 2013 at 7:18pm

It would be possible to use a recursive approach to accomplish this - either through hoopsnake or some other way. But I would recommend something a little more "grasshopper":

If you can find the transform for each object in the series to be aligned to the next object in the series

(A -> B) (B -> C) (C -> D) (D -> E)

Then you can use some list manipulation and other tricks to find compound transforms. essentially:

Move object D by the transform (D -> E)

Move object C by the transform (C -> D) + (D -> E)

Move object B by the transform (B -> C) + (C -> D) + (D -> E)

etc.

See the attached definition. The bulk of the work is actually in finding the individual transforms - once you've got them, composing the compound transforms is pretty quick.

Hope that helps - let me know if I can clarify anything!

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