# Patch-Command

Hello,
im looking for some more information on the “patch” command. I am interested in knowing how it interpolates points to create surfaces. Does it use Kriging, Minimal-Curvature, Inverse Distance to a power,…? ( Those are some of the Gridding-Methods i know of). Are there any publications on the Mathematics behind Rhino`s Patch command?
Nils

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We have no published information on how the Patch command calculates a solution. Why do you need this? What problem does this help you solve?

– Dale

There is no problem to be solved here. It just helps me to document how i created the surfaces for my task. I dont need any “in depth” analysis (even though i would not mind those) - the name of the algorithm would be sufficient.
Regards
Nils

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Good day @dale,

Currently i’ve modelled a single unit cell of the kirigami auxetic unit cell and patched the resulting hole after the unit cell rotates. I would like to also understand how the patch command controls the control points and whether i can tune them to match those described in the supporting information of https://www.nature.com/articles/s41563-019-0452-y.

-Samson

Hi @meta.gear,

I have no idea how to begin to answer this. Perhaps you can show us what you have and what you are trying to achieve?

Thanks,

– Dale

Good day Dale,

mahadevan to curvature debug v3.gh (114.5 KB)

In the auxetic structure, i’ve patched the “hole” with the patch command.

Try to grab the surrounding panels as they rotate as a four bar linkage in 3D, and the geometry of the patch/ curvature will change depending on the configuration of the 4 boundary edges of the hole.

In the paper’s supporting information ( Programming shape using kirigami tessellations | Nature Materials), they propose to patch the hole with a bezier bicubic patch, with the inner 4 control points to be calculated by the 12 outermost nodes that coincide colinearly onto the 4 boundary edges of the surrounding panels.

I’m hoping to enforce the same method of calculating the control points to understand the curvature of the resulting patch.

Sorry if first post wasn’t too clear, i’ll try my best to provide more details if required. Thank you for taking the time to help and reply, much appreciated.

Best Regards,
Samson

Hi @meta.gear,

No, we don’t create patches in this manner. If you require this specific algorithm for patching, you’ll need to write it yourself. The SDK should be rich enough to do that if you are willing to do the research into the algorithm.

– Dale

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