Grasshopper

algorithmic modeling for Rhino

Culling steep surfaces

So I have a landscape made of poly surfaces and I want to remove all surfaces above a certain gradient. Is this possible.

 

I've tried finding the surface normals but they are either straight up or incorrect.

 

In the attached definition I have tried to flip the normals of down facing surfaces and then analyse all surfaces and select only the surfaces with a small angle difference to another vertical vector.

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Permalink Reply by Danny Boyes on May 25, 2010 at 5:17am
Hi Johnathan,

You could use the the vComp Component to decompose the normal vector and generate a cull pattern based on the Z component only. And if you used the abs value you wouldn't need to worry about upside-down surfaces.

Permalink Reply by Johnathan Guest on May 25, 2010 at 6:24am
Thanks Danny, has saved me a lot of time of trial and error!

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