how can I create metaball like surfaces?

I'm tring to crerate a diagrid for a metaball shaped building.

I know it is not possible to create a solid or a surface metaball but is there another way to create a metaball like shape that allows you to make a surface. I found some fake metaballs here http://www.grasshopper3d.com/forum/topics/freeformmetaballthing-1 but there is no explanation on how to create that sort of shape.

If not does someone know how to create a metaball diagrid?

Thank you!

Picture of the fake metaball I'm trying to create.

Attachments:

fake metaball.png, 514 KB

Replies to This Discussion

Permalink Reply by David Stasiuk on August 1, 2013 at 12:55pm

One option would be to generate your metaballs as a general mesh first, and then to drop a diagrid mesh over the top of it using kangaroo, and trim the mesh around where it crosses your ground plane.

I can get you started on the metaball meshing: http://www.grasshopper3d.com/profiles/blogs/metaball-meshing and there is a sample file here: http://www.grasshopper3d.com/group/kangaroo/page/example-files that has a fabric drape example in it.

Permalink Reply by SIMON ESCABI SANTOS on August 1, 2013 at 4:17pm

David your definition is great but what i need to do is to convert the metaball mesh into one continuous surface so that I can then aplly Sebastian L.'s diagrid like lines definition.

Permalink Reply by David Stasiuk on August 1, 2013 at 11:11pm

That's why it's a two-part modelling problem :) The metaball mesh is just a scaffold....you'll want to "drape" a diagrid over it now using kangaroo...it's a tricky affair.

Permalink Reply by David Rutten on August 2, 2013 at 1:18am

It's also an impossible affair in some cases. The topological genus of metaball surfaces (meshes) can be any number between zero and something very very big. Nurbs surfaces can be either genus 0 or genus 1.

In other words, if you've got a metaball mesh with two or more holes there's no way on earth you'll be able to turn it into a single nurbs surface.

David Rutten

david@mcneel.com

Tirol, Austria

Permalink Reply by SIMON ESCABI SANTOS on August 2, 2013 at 8:52am

Thank you David.

This is a picture of the geometry I'm working with. It appears to me me that it has a genus 0.

What I want to do is to me able to apply a divide surface command on grasshopper. For that I need the geometry to be a single smooth surface and not a faceted nurb surface because it will divide every single face insted of the entire metaball.

Thanks!

Permalink Reply by David Rutten on August 2, 2013 at 4:02pm

Yup, that's genus zero and you will -at least theoretically- be able to patch a nurbs surface through there. You have to be careful with the seam and poles, but basically if you rebuild a sphere surface and move the control-points over the metaball shape then you can approximate it.

There is no component for this though in Grasshopper, though I suspect Daniel Piker's Kangaroo plugin can probably handle it.

David Rutten

david@mcneel.com

Tirol, Austria

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