Morphing a box: how to get better?

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Permalink Reply by Leonardo Roli on March 13, 2015 at 10:54am

Hi everybody,

I'm still working on this definition, but I've the following problem:

I need to subdivide the BRep surfaces, in order to design the building's facades, but when I [DeBrep] the volume to subdivide it, it happens this:

In other words, the central hole is extruded to a height greater twice times, compared to the rest of the building. This happens because in the previous steps of this definition, the central hole has been build in this way:

so, my question is: how to select only the lower parts of the hole's s surfaces?
I've tried to use [List Item], but it doesn't work.

Permalink Reply by nikos tzar on March 17, 2015 at 6:18am

Hi Leonardo,

This is the problem you are facing and there is no universal solution for it:

http://www.grasshopper3d.com/forum/topics/dividing-a-trimmed-surfac...

http://www.grasshopper3d.com/forum/topics/trouble-with-trimmed-surf...

http://www.grasshopper3d.com/forum/topics/help-with-dividing-a-surf...

http://www.grasshopper3d.com/forum/topics/division-of-trimmed-surface

The thing is that a trimmed surface will always "remember" the untrimmed surface it comes from. So for operations like [divide] you will have to rebuild it so that you can have an untrimmed surface to work with.

Permalink Reply by nikos tzar on March 17, 2015 at 6:42am

Here is one way to rebuild the surfaces in your case:

Attachments:

• Box-Morph.gh, 25 KB

Permalink Reply by Leonardo Roli on March 17, 2015 at 12:53pm

Wow.. that's impressive and I'll never get there without your help..
I was just trying to convert the brep into a mesh and then to [isotrim] it.. and obviously it doesn't work. 

But.. are these the only ways to do it by using the default Gh components or are these the only ways to do it and this is all the story?  Because I've installed Lunchbox and Weaver Bird, hoping that would serve.. but again: they recognize just a single surface and not an entire BRep.

I know that probably you're gonna hate me, but I've a further question: in your last definition, all the surfaces have the same number of subdivisions, independently from their length. Is it possible to subdivide all the surfaces with the same subdivision length?

Maybe I could make thing easier if I'll show you the final result I'd like to achieve:
A lot of continuous and edgeless pillars that wrap the building

(I guess that in order to smooth the shape like the one below I'll could use Weaver Bird)
Thanks a lot

Permalink Reply by nikos tzar on March 17, 2015 at 1:37pm

Hi Leonardo,

See David's response for dividing a surface "equally" in this post.

If you search the forum for "divide surface in equal parts" you will find many other suggestions.

But before getting into that, make sure that you want them divided this way because I don't think this logic matches the image you have posted. For example, if one side has 10 stripes and the opposite has 8 you won't be able to have continuous stripes around your building...

As for the trimmed surfaces issue, I am afraid it is the way it is. so if you know this is going to cause trouble later on in your definition, you should take a step back and see if you can create your shapes with untrimmed surfaces in the first place.

Permalink Reply by Leonardo Roli on March 18, 2015 at 8:09am

Hi Nikos, you're right.. each side must have the same number of subdivisions..

Now I'm working intensely on your last def and I hope to share soon the final result.

Previously I asked you if it was possible somehow to subdivide an untrimmed BRep, because some days ago I worked on a nice def that Hyungsoo Kim shared with me in this discussion.. leading my to this result, in which I've combined your editable brep with his voronoy structure:

here the def:

this made me think that it was possible to recreate something similar without using the 3DVoronoi component.. but ok, I give up :D

Permalink Reply by nikos tzar on March 18, 2015 at 9:31am

just for clarification:

a brep is not the same as a surface. you can think of it more as a group of surfaces (or a polysurface as rhino calls it).

So a brep can have both trimmed and untrimmed surfaces, like it does in your case (the external walls are untrimmed and all the others are trimmed).

Some components (like 3DVoronoi or Contour) work on breps and others (like DivideSurface) work on surfaces. the later can create problems if the surface is trimmed...

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