Select each second Box rectangle out of a list

Hello, new Grasshopper here, since last weekend :)

I've been trying to solve this thing for about ten hours now, so it's time to ask for help.

The outline of what I want to achieve is that I have a Curve. In this Curve I have defined the points, I exploded the segments and have added a Perp Frame on the ends of each segment.

Oriented on each Perp Frame I have created a Rectangle from which I have drawn a Box Rectangle.

Each 'other' (odd or even, or each 'second' rectangle in the list) of these rectangles needs to get a negative length value so it doesn't point outward of the curve, but instead so that it has it's length perpendicular to the segment.

So, eventually I want to make it so that each segment has a Box Rectangle placed on it's outermost point, pointing inwards. Half of these Box Rectangles is already oriented in the right direction, but I don't know how to single out half of them, or construct two lists with the 1st, 3rd, 5th, 7th, etc. and the 2nd, 4th, 6th, 8th etc.

I have added screenshots, I am making this as a personal project for a school project on the Art Academy and am really eager to learn to master this Grasshopper a bit more.

Before trying to do it this way, I tried to do it with Sweep1 Rail, but could not get the orientation along the segment, and also I didn't manage to find out how to limit the Sweep1 Rail to a certain distance (like 30mm for example).

I had imagined this should be done by projecting a second line of 30mm from a segment outer end inwards from both sides and using this second 30mm long line to put the Sweep 1 Rail on. Then I could close the ends, do a Union, Merge all Faces and be done.

However, I couldn't figure it out and the method I'm trying to solve now has gotten me further down the line of the process.

The next step in my process will be to be able to generate a structure on a point of a curve where I can project a certain shape on. Then I want to export this collection of shapes as an STL and 3D-print them. (I have built 2 3D-printer all by myself).

The parts are connectors to connect cheap aluminium extrusions together with minimal effort so I can start prototyping a shape for a small carriage I am designing.

If my explanation is unclear, please tell me, I am new to this, and my mother-language is Dutch, so mathematical terms are a bit difficult for me to understand, but please do use diffcult terms in an explanation where needed. I can only learn :)

Hi from a very happy new user of Grasshopper!

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Replies to This Discussion

Permalink Reply by Marinus de Beer on March 26, 2014 at 6:55am

OKay, I fixed it, deleting and replacing the Shift List with a new one now makes it possible to use -x..

Somehow now the loft doesn't work in the end.

It says:

"Loft failed, I don't know why"

Somehow I think the older component got bugged? Or did I not connect the wires in the right order? Can that cause a problem?

I have the file saved if anyone is interested in it, maybe a bug, maybe my own dumb fault.

Attached the loft that doesn't work:

Here is the file:

http://s000.tinyupload.com/index.php?file_id=76350223129568238097

Permalink Reply by Danny Boyes on March 26, 2014 at 8:46am

Hi Marinus,

You have the default value in Count of [PFrames] change this to one and it should work as expected. (my fault)

Permalink Reply by Marinus de Beer on March 30, 2014 at 3:54am

I'm getting more and more into this, thanks Danny, I've also found a way of using [Offset] and [Loft] together with some preset sliders to get the correct design (and then union, mergefaces etc).

Besides that, I am also trying to apply this component set to another type of aluminium extrusion.

The first extrusion was a U-shape extrusion, the second type is Square-shape, which might give me a stronger frame, but also makes it heavier and bigger.

It's really interesting to really try to create something that will be realized instead of just making a nice looking render. Most people I know are just putting in some random components to make impressive images and then visitors look at it for a second and think 'wow' and then walk on.

I see Grasshopper as a tool for Rhino and not as a generator just to create random weird images.

It's great to see that Grasshopper can do all this!

Permalink Reply by Marinus de Beer on April 2, 2014 at 1:57pm

Danny, I have managed to create exactly what I want. I can now make any kind of rectangle and apply my Grasshopper script on it.

However, when the line doesn't have 90 degree corners (freedrawn lines), Rhino and Grasshopper crash when I select the curves.

My script is included in this message, I hope you understand why this is?

It is quite strange that it is crashing my whole program.

Attachments:

connector_finished_1.gh, 26 KB

Permalink Reply by Marinus de Beer on April 5, 2014 at 3:00pm

Hi everybody, just a small update;

I have managed to almost completely make grasshopper produce the correct object now.

Here is the eventual result:

I want to thank Danny so far for helping me out. Currently there is still some more I want to do with this object (my challenge is to add a 3rd vertical connector on each generated part).