A Single NURBS surface - how do they do that?

Hi fellows,

I would like to share my findings on organic roof surfaces like some of the neo-Gothic churches and Shigeru Ban types of building.

The Base Roof surfaces of these complex all seem to be constructed with 1 NURBS surface, not from patches or polysurfaces.1 single surface allows perfect curvature to be achieved, grasshopper usage which is really efficient.

As for the Pompidou Metz roof, it starts with a mesh model with nice topology and then the mesh is handed to a company (iCapp) which "magically" rebuild the single NURBS surface from the point clouds or mesh file. Some info could be found here:

http://www.icapp.ch/2.Ebene/3menue/eservices_details.html - scroll down to the part of "architecture"

Another article here that talks about the importance of single nurbs surface:

http://architectureinsights.com.au/media/uploads/resources/ByeraHad...

My Question is..how do they ever do it - 1 single NURBS surface?

Related GH discussion:

http://www.grasshopper3d.com/forum/topics/fillet-merge-poles-to?pag...

http://www.grasshopper3d.com/forum/topics/how-can-i-merge-serfaces?...

http://www.grasshopper3d.com/forum/topics/one-more-push-before-the?...

(but i cannot find thorough discussion about surface creation)

Replies to This Discussion

Permalink Reply by Jeffrey on April 17, 2012 at 9:01am

From Mesh --> points --> NURBS surface :

http://www.icapp.ch/2.Ebene/5PDFs/Panelshop_Tools_en.pdf

Section 7 talks about the technology that the company use..but it starts getting into Reverse Engineering Field.

What is the a way to construct these roof surfaces in rhino without going into reverse engineering field?

I've tried something like Resurf but it doesn't really seem to work well with these roof surfaces..

Permalink Reply by Jeffrey on April 17, 2012 at 9:11am

A Chinese rhino user did the model without grasshopper...but still I have no clue how he drew the lines...

More images: http://blog.shaper3d.cn/dixon/page/2/

Permalink Reply by taz on April 17, 2012 at 12:53pm

This discussion could be helpful:

http://www.grasshopper3d.com/forum/topics/converting-tri-poly-mesh-...

Permalink Reply by Dimitrios Polychron on December 20, 2014 at 3:51pm

iCAPP and Resurf are what you would need to truly make it a "continuous" surface. I think that the software uses point clouds though, so maybe converting the mesh first into a point cloud would produce the best results?...not sure. In terms of manually modeling though I do not believe that it is possible to get a single surface with just Rhino.

Anyhow, I found that the best method for creating these surfaces manually is using Tsplines, which gives you the flexibility of push pulling surfaces but limits you since tspline surfaces are always quads (but by manipulating the surface in control point mode and "cylindrifying" your points you can make "rheotomic" lofted funnel forms pretty easy). Of course you have to split your surface in the end to get the openings in the funnels.

The only other method I know of us making a base loft, and then projecting curves onto the base surface, and then using those curves to loft more surfaces that are tangential with your base surface. The first image above shows a surface that was produced this way.

I would use Tsplines though.

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