Checkerboard pattern?

Hi everyone,

Very new to Grasshopper here - I'm trying to do something that's probably quite simple, I just can't seem to find what I'm looking for.

So I have a surface, I've divided the domain^2 and made a matrix of subsurfaces from that. Simple. What I want to do now is select a checkerboard pattern in that collection of subsurfaces. Simply adding a 'cull nth' set to every other number selects whole rows of subsurfaces in the 'v' direction. I know this has something to do with the way the data is organized as it exits the isotrim icon, but I don't know how to augment that data to 'reset' it to achieve the checkerboard. Any suggestions?.

Replies to This Discussion

Permalink Reply by David Rutten on March 13, 2010 at 5:16pm

Hi Brorstein,

Using a Culling component, you can remove specific items from lists of data. If all your items (sub-surfaces in this case) would be in a single list, then a Cull Nth component would generate a checker pattern, provided there are an odd number of items along each side.

If your items are stored in separate columns, you'll have to operate on each column individually. You can either generate multiple series of numbers, starting at zero and one alternatively, or you could create different culling patterns.

--
David Rutten
david@mcneel.com
Poprad, Slovakia

Attachments:

CullChecker.png, 210 KB

Permalink Reply by Daniel Piker on March 13, 2010 at 5:24pm

Here's how I get around this :

where the expression is (a*c+b*d)%2

Permalink Reply by Brorstein on March 13, 2010 at 5:33pm

Nice! Thanks David and Daniel for the quick responses. I've already succeeded with David's technique. Daniel, I'm going to set up a scenario like you've posted and work through exactly what's happening at each component. This plug-in is like a crash course in a lot of math I've forgotten. :P

Permalink Reply by Daniel Piker on March 13, 2010 at 6:25pm

You got me started playing with checkerboards again :

Permalink Reply by Brorstein on March 13, 2010 at 9:27pm

Showoff!

Another n00b question: the 1-rail sweep component seems to default w/ freeform. Is there a way to get it to the equivalent of roadlike top?

Permalink Reply by Brorstein on March 13, 2010 at 9:59pm

Not to keep bumping this thread, but I just figured out that a 2-rail sweep with a second rail holding the hand of the section basically does what I was intending - but I'm still curious if there's another workaround for 1-rails or not.

Permalink Reply by kleerkoat on September 13, 2011 at 8:46am

really!

Permalink Reply by Vami on December 17, 2013 at 6:48am

Hi Daniel,

Could you tell me how are you doing this?

Permalink Reply by Arthur Mamou-Mani on September 13, 2011 at 7:50am

Hi Daniel,

Thanks a lot for this trick, it works perfectly!

Could you explain how (a*c+b*d)%2 works ? what is the % for ?

Is there a way to get the culled faces?

Many thanks,

Arthur

Permalink Reply by Adi K on April 10, 2016 at 4:20am

I tried using this expression but it tells me that the expression ( (a*c+b*d)%2 ) can't be used in an If expression. How did you use it so that it can be used as a Boolean input for the cull component?

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