# Using Geometry Nodes, how can I flip every other point in an array?

I'm quite new to Geometry Nodes -- please forgive the ignorance!

Here I'm using a Line node for a point instance array. The object I'm instancing, for this demonstration, is a rudimentary arrow and monkey. Note how the Line node's "Count" integer is linked to the Group Input. Having control over the exact number of instances is important to my procedure, as the number of required monkeys could range anywhere from 1 to 25, or more.

What I'd like to accomplish with geometry nodes is to flip (-1 on the X axis) every other instance of the object, like so:

I've searched around, and the only clues I've found involve randomly assigning transformations. What I need to accomplish, however, is an alternating pattern between two per-determined transformations (1, and -1).

Any help would be appreciated!

• just a hint for future questions: please do write all restrictions and prerequisites in your questions and don't think they are kind of self-evident. we (who want to answer) cannot read your mind and so we both don't waste our time on answer you cannot use. Aug 20 '21 at 7:47
• Absolutely! Thank you very much for your help. I'm quite new to all this, but I'll try to be more thorough in future questions. I hope it wasn't too much trouble for you to rewrite your answer! Aug 20 '21 at 10:17
• you are welcome! Aug 20 '21 at 14:33

One thing i am pretty sure of, now you will update your question again and say "yeah, but the offset isn't working now". Yes, but you didn't say that in your question too ;) But here is the solution for your next (future) question update:

UPDATE: new solution for added new restriction to question:

result:

you can do it with this node setup:

result:

It just copies the point instance again, but rotates it (point rotate) and moves it (point translate) before instancing.

• This gets very close to my goal! However... the only problem I have with this solution is the fact that increasing the Line node's Count integer increases the number of monkeys by two, instead of just one. I'll edit my post to better reflect that control over the exact number of instances is part of my goal. I didn't realize a solution could be this straight-forward, but I will try to find a way to make it viable for my application! Aug 20 '21 at 3:51
• i update my answer Aug 20 '21 at 7:28

Even Chris answer is correct, I think this is too complicated, so I decided to make a simpler node setup:

The key function of this setup is modulo function (Attribute Math node). It produces 0 value on every odd point, and you can use it to rotate every even point.

BTW if you want to rotate on 90 degrees, just type pi/2 in the field

UPD. @Chris: It's not a big problem. You can achieve this by this setup:

• Although Chris's answer is already working for my project at the moment, I'll give this one a whirl as well, once I get the chance. Thank you for answering! Aug 20 '21 at 10:20
• @Crantisz: well done! +1 Aug 20 '21 at 14:55
• just a small remark: if you would have taken the offset as vector as i have, i think you would have needed 1 more node too....😉 Aug 20 '21 at 14:58