linking a trimming plane to each individual element in a list

Hi, I've been using grasshopper for 3 weeks now and I'm still learning about its capabilities.

I am working on a geodesic sphere and have started by firstly creating the spherical path and then orienting a single solid (a tetrahedron) into multiple locations around it.

The only problem is that I now want to truncate the tetrahedra such that the level of truncation gradually varies along the sphere from left to right... I've managed to use the remapping function to specify each distance from a pt to the centroid of each solid.

My question now is whether there is a way to orient a single trimming plane in exactly the same positions as all the tetrahedra (I've managed this also) but also force each plane to trim only its corresponding tetrahedron rather than any adjacent ones. ie. for example to link plane 1 to tetrahedron 1 only, plane 2 to tetrahedron 2 only etc.

Would greatly appreciate any help on this matter :).

Pls note that in the image the truncated tetrahedra were trimmed from the original solid and NOT after orientation around the sphere.

Replies to This Discussion

Permalink Reply by Vicente Soler on March 24, 2013 at 5:33pm

There is no component to trim a brep with a plane in GH.

You might be able to place boxes on the corners and use the boolean difference component. You might have to post the definition to be able to help you, but in general the data structure of both tetrahedrons and boxes must match.

Nevertheless, the best way to do this if possible is to not trim any geometry. The lunchbox plugin has a tetrahedron component with a truncate parameter.

Permalink Reply by Sacha Cutajar on March 25, 2013 at 7:05am

First off, thanks for the reply :).

hmm I see, although I did manage to trim the first tetrahedron with a plane. I did it that way in order to be able to move the trimming plane up and down and have control on the truncation of the solid and it worked. That's why I was wondering if maybe it could also be done globally across the entire sphere :).

As for creating boxes, hehe I've actually tried that out and with solid difference it works, although the problem is that the boxes affect also nearby tetrahedrons so you end up with unwanted trimming in some parts....in this case I need a way maybe to associate each box with each tetrahedron. It's probably a matter of specifically listing the elements although I have no idea how to do it.

It would be great if I can manage this because the next step is remapping, where the boxes will be gradually placed at different heights upon the tetrahedra so as to give varying truncation, which will vary by the relationship of distance between the boxes' centroids and a point. Surprisingly this worked as well, but again, due to the previous step I am getting that unwanted trimming and it just ends up very messy.

Id post what's happening in grasshopper although it's a bit long winded, but if the image is not clear I'll try and clean up the GH functions and post an image of the last procedure. :)

Permalink Reply by Vicente Soler on March 25, 2013 at 7:22am

Each tetrahedron must be place in its own branch (using graft, for example). Each set of boxes that correspond to a tetrahedron must also be placed on a different branch. You must end up with the same number of branches for tetrahedrons and boxes. There should be one element per branch in the tetrahedron data structure, there should be multiple elements per branch in the boxes data structure.

Permalink Reply by Sacha Cutajar on March 25, 2013 at 7:27am

great! thanks a lot, I'll try it out and let you know how it turned out :). Thanks again.

Permalink Reply by Sacha Cutajar on March 25, 2013 at 3:44pm

it was a success. Thanks one last time hehe :)

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