Generating a crushed metal surface

Hi,

I am trying to find a way to create the surface of crushed metal in Grasshopper. How could this be done?

So far, I have only done it in Rhino itself, simply by generating a large "mountaineous" plane with the heightfield command, and then moving control points closer together to create kinks. It is a very time consuming process though of course, and it's hard to remove all the waviness of the surface as crushed metal would rather be straight than wavy in between the kinks. Thus my results look too close to a sheet of silk lying on the ground.

I am very grateful for any ideas on what other ways I could go. It would be especially helpful to move the whole process into Grasshopper to produce faster and yet more flexible results.

Thanks in advance.

Replies to This Discussion

Permalink Reply by David Rutten on October 12, 2013 at 4:44am

How do you decide which control-points to move and what direction to move them in? If you can explain that mental algorithm then perhaps someone can translate it into a grasshopper algorithm. It'll still only give you the silk shapes, but it may be a good start...

Nurbs surfaces don't like to get forced into kinks, even though it is possible to do it using weights, multiple knot or overlapping control-points. To simulate the actual bending and buckling of a metal plate under forces you'll probably have to use a mesh for the deformation simulation.

David Rutten

david@mcneel.com

Tirol, Austria

Permalink Reply by Duncan W on October 12, 2013 at 6:14am

Thanks for your response David.

I also get the feeling Nurbs surfaces are not happy to do this. What I've done is to make out the lines that would ideally define the kinks and then moved adjacent control points closer together that sit close to these lines, usually in pairs of three, and sometimes 2 to create a softer kink. When done, I tried to straighten out the parts between the kinks to make them look straighter and less roundish.

So one idea I had was to generate kink curves in top view over a surface in GH, and then use control point XY distance to decide which control points are pulled close together into mentioned pairs along the curves.

The buckling you mentioned is exactly the problem. Can you tell me more about what you mean by using a mesh itself? I've never worked with meshes to be frank. It's always been Nurbs for me.

Permalink Reply by David Rutten on October 12, 2013 at 12:08pm

Moving control-points based on distance from a group of curves sounds very do-able:

Meshes are the geometry of choice for physical stress calculations. It's much easier to write an algorithm which computes the forces that flow through a collection of quads and triangles than it is to write an algorithm which handles forces through a curved nurbs surface.

David Rutten

david@mcneel.com

München, Germany

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