generating a nurbs surface from a smoothed mesh

Hello all, I have a smoothed mesh which is generated by 3 sphere like shapes. I am trying to generate a nurbs surface where I can panelize and add structure. My enitial thought was to take the mesh and extract section curves, then use those curves to rebuild a nurbs surface with UVs. The surface on the right is a surface generated with the patch command in Rhino. I dont know much about how the patch command actually works but its pretty funky in a few zones.

Another thought is to use the "surface from points" command but Im having a little trouble getting it to work with my points. Do the points first need to be generated from a grid?

I also looked at JellyFish but using a magnetic force to create the surface is pretty tough to control.

So really I wanted to see if anyone has some insight as to how I can take this mesh form and rebuild it as a nurbs surface by using the surface from points command, or something like Jelly Fish with displacement or some other method that may be out there. I am not stuck on having a rib like structure so I would be more than happy to here any other suggestions.

Thanks so much for youre time.

Replies to This Discussion

Permalink Reply by David Rutten on September 23, 2011 at 11:54am

Hi Charles,

this will require both fitting and trimming. The Patch command is pretty good at that. Patch has been exposed in the Rhino5 SDK, so if you have Rhino5 you may be able to script this.

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Charles Aweida on September 23, 2011 at 12:29pm

Thanks for the reply David, I used the patch vb script from this post but the surface seems to do some strange things. I guess maybe the patch command is inherently less accurate than other methods?

Permalink Reply by David Stasiuk on September 23, 2011 at 1:00pm

If you want to do the surface from points, you definitely need to have the same number of points in the U direction...so your point list has to be carefully generated so that when it's flattened data, your points line up in the correct order.

It's a bit of a workaround, but if the bottom of your mesh is cut on a plane, you could create a planar surface around it at its base and convert that to a mesh. You then split the bottom mesh and knit it together with your initial geometry to give your mesh a sort of base. Then you could cut sections of the plane along the edge of that base, and split the ensuing polylines into points, which you could then make into a surface from points. Finally, you use the base profile to trim your surface. I've used a technique like that to convert topo lines into a nurbs surface for a site model, and it works out pretty well, particularly if you up the count of cut planes and/or get creative with how you divide the cut polylines for your nurbs surface from points.

One thing you could do is give your mesh a bounding box and create a grid of points on the bottom surface and shoot rays through the mesh. You replace your base surface points with intersections from your mesh/ray operation where they exist, and use that as your grid of points for a surface...then do the edge trim.

Permalink Reply by Adam Fenton on September 25, 2011 at 5:25am

Hi David,

Is there any chance of posting that definition you're describing because I am trying to do the same thing (convert a mesh to a surface) as I am new to grasshopper. Many thanks!

Adam

Permalink Reply by Adam Fenton on September 25, 2011 at 5:33am

This is the mesh I am trying to make a surface (attached)

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