Creating overlapping collections of points

Greetings,

I am working on a gridshell design, where the base structure and pattern will have an overlay of shingled elements. In order to create the overall form and elements for eventual fabrication, I have been working through understanding the offsets and center points for the structural shell. This seems to be working well enough to save those questions for later. The difficulty I am having is in creating collections points (from either the intersections of the surface grid, or the center points of the surface normal of the surface grid - I haven't decided which one to use yet) that overlap. By this I mean that in a GH data tree structure I want to select the points:

{0,0}[0]

{0,0}[1]

{0,1}[0]

{0,1}[1]

This will create a four sided polygon (not necessarily square, rectangular, or parallelogram because of the underlying surface geometry). The selection set would be repeated, advancing one step up in each tree, so the next polygon would be the following points:

{0,0}[1]

{0,0}[2]

{0,1}[1]

{0,1}[2]

This would be repeated until all of the points in all of the trees had been selected to create individual polygons. I hope I am annotating the points in the data trees correctly, in order to describe the desired geometry. I have tried several methods (culling patterns, sifting patterns, etc.) without too much success. I am hung up on creating the expression for the base selection set in such a way that it can be repeated across the collection of points on the surface.

One screen shot of the geometry and one set of points for the polygon are included along with the GH and Rhino files.

As usual any and all suggestions are much appreciated.

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Replies to This Discussion

Permalink Reply by martyn hogg on May 1, 2015 at 12:46am

There's something similar in the definition I've attached. It takes points 0 & 1 and 1 & 0 from a pair of closed polylines and then pts 1 & 2 and 2 & 1 (keeping a clockwise rotation around the resulting mesh face.) and so on until it has gone all the way round each set of polyline points.

(I'm hopeless at tree notation so haven't tried)

Perhaps this can help. It uses the length of the lists of polyline points to determine how many sets of points to return because each closed polyline in my definition can have a different number of points. You might not need to do this if your point lists are all the same length.

Attachments:

Voronoi_smooth.gh, 146 KB

Permalink Reply by Gregory D Thomson on May 1, 2015 at 9:44am

Hi Martyn,

Thanks for the definition. I will take a look at it to see if I can adapt it to my needs. In my example here each of the closed polylines will only have 4 points, though that could change in the future.

Permalink Reply by Gregory D Thomson on May 1, 2015 at 2:02pm

Hi Martyn,

Being the GH rookie that I am, it is taking me some time to decipher the workings of your definition when I apply it to my geometry. I am still working on it though. I have also tried some of the paneling tools plug-in pieces to get a bit closer. It's not quite a perfect fit for what I am looking for, but it's a good start.

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