Flipping z axis!

Hi all, Im working on a script for a sculptor friend of mine whos working on an instalation using half mirror pannels suspended in an atrium. The idea is that the triangular pannels spiral down and then back inside the form and are proportionally oriented towards a point attractor. Im having problems with the z axis flipping when the planes are reoriented with the tangent vector at the parrameter point of the planes origin. I know this is a bit of an issue in grasshopper and have tried a few fixes already but I cant seem to make it work, if anyone has a better idea and can help out that would be great. the idea is that they should look like they are flowing down the spiral but are being pulled towards the point attractor as they get nearer it.

I was also hoping to adjust the ammount of orientation of the planes towards the attractor point by using the relative parameter on the spiral curve, so that in the tight section as the curves move towards the center they are almost totally oriented by the surface normal and not influenced by the point attractor at all. this way they would have a fairly ordered spiral inside the form and more chaotic on the external surface, any ideas how to do that?

Any help would be greatfully appriciated,

Kind regards all


my website if anyone is interested

sculpture form z axis flipping problem.gh (31.3 KB)

Hi @colinandrewrennie

I am having a hard time picturing what you are looking for with the second part of your description of the attractor. Maybe a sketch might help.

In the meantime, I added to your script to fix the Z orientation of the planes. This is done by comparing the vectors or the flipped and unflipped Z in the group that is turquoise in colour.
matching Z.gh (33.1 KB)

For the attractor, you would have to use two remap functions, one for how much it is affected by the attractor and another for how much it is affected by the spiral. But that is all I can infer.

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Thanks Christopher,

Sorry it took a while to reply, Im working on this in my spare time and very much appriciate yours,

Ive had a look at the srcipt addition you did, and although I dont quite understand how it works, it seems to work in most instances, ive worked up the design now, seem to have managed to solve a few issues with the allign planes component.

Your efforts to help with the allignment were invaluable, tbh im still working out the system you used but it has taught me a lot.

Big thank you!


Hi Colin,

I used the planes that you previously noted were in the correct orientation.
I then used the point orientated to create a point in front and behind and then compared it with how close it is to the point created from the correct orientation. This gave me the true false list of which of whether or not to use the flipped plane.


Hi Chris, thanks for the explanation, and apologies for the super late reply, Ive managed to get the system working now properly with your help, unfortunatley I cant release the script just yet as the sculpture is still not signed off due to all the coronovirus lockdowns but I havent forgotten your help and advice at all,

stay safe,