question on isocurves

Hello-

I have been trying to figure out a way to create isocurves (from a surface) that would concentrate or repel around certain influence points.. similar to what you would see on a weather map. I have been using Daniel Piker's JellyFish tool as a starting point but so far have fallen short on any usable result. Any guidance on how to accomplish this would be most helpful. I have attached an image I found on the internet as an example of what I am after in grasshopper. Thanks!

Attachments:

MarchingSquare.png, 65 KB

Replies to This Discussion

Permalink Reply by David Rutten on July 9, 2011 at 12:15am

Hi Jonathan,

what exactly is the input for the image you posted? Is it already a set of curves that you want to deform based on attractors, or are you looking to create the curves from a collection of 'summit' or 'pressure' points?

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by jonathan heckert on July 9, 2011 at 11:31am

Hello David,

The image was an example created by another person, and unfortunately I'm not
completely sure how it was constructed by them.. For my purposes I am
trying to create the lines from a set of pressure points that I can
control the strength and location of in grasshopper and rhino. I had
attempted this by using points to manipulate the curveiture of the
surface and then trying to extract the topography like isocurves from
there, but I couldn't figure out a way to get the isocurves to display
properly on the surface. Or at all really. Hope this helps clarify,
thanks for your help! It's very much appreciated!

Permalink Reply by David Rutten on July 9, 2011 at 12:31pm

Since the image is called "Marching Cubes" I'll blatantly assume it's in fact a set of iso-surfaces (I know they're only curves, but calling them iso-curves confuses them with Nurbs surface iso-curves, better to stick to the official jargon here).

Grasshopper has three MetaBall components which do exactly the same thing*. You supply a number of charges and then a value for the iso-surface section. One component allows you to specify weights per point, but negative weights are not supported. All you need to do is create metaballs with a range of different iso-values to get the family of curves like in the image you posted.

Another approach would be to deform a surface or mesh -i.e. assign a specific Z value to every control or mesh point- and then section the surface/mesh at different elevations.

David Rutten

david@mcneel.com

Poprad, Slovakia

*I cannot send you a file as I'm using an internal newer version and you won't be able to open it.

Permalink Reply by jonathan heckert on July 9, 2011 at 12:59pm

The MetaBall component is very interesting, I think I'll play around with this for a little bit and see where it goes - thanks so much for your help.

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