Nurbs Modeling like Poly Modeling?

Rhino
1

Hello,

Does anyone know of a way to model Nurbs polysurfaces similar to a polygon modeling workflow i.e. by grabbing a shared edge between two Nurbs surfaces, manipulating it and having both surfaces update, but maintain C0 connectivity? I’m familiar with the mesh modeling function within the SubD modeling tools and the ability to manipulate curves with history attached to surfaces, just not a way to model directly on CV points on a surface edge and have a second joined P0 surface follow along.

Thanks,

2

Hi Justin - it is not inherrently a surface friendly kind of workflow just because of the way these are structured. It can work if all the forms remain more or less blocky with planar faces - you can do this type of editing now by selecting edges and faces and moving or Gumballing but it is not very robust when things become non-planar. (mesh triangles never do that)
That said, see the thread on PushPull modeling on the Serengiti forum to see what we are working on in this general area.

-Pascal

3

Great, I’ll look into it. Thanks Pascal.

4

Also, in terms of use case scenario I’d mainly be interested to use this approach to block in the overall volumes/silhouette of a design with planar surfaces, then transition to sculpt with curvature. This way you could skip needing to draw curves to generate new surfaces. It would be great if the mesh modeling function in the SubD toolbox could leverage the ‘convert object to nurbs’ tool without smoothing the resultant Nurbs surfaces. As long as the input SubD mesh is built with quads, it seems like the generated Nurbs surfaces could still be faceted and water tight. Maybe during conversion there could be an option box to select the point/degree count of the generated planar surfaces. However, any subsequent surface modeling would probably still require traditional sculpt and match process.

5

Create a SubD mesh

ExtractControlPolygon to convert the SubD mesh to a regular mesh

MeshToNURB and select the regular mesh
Result is a polysurface with degree 1 NURBS surfaces

Explode the polysurface

Select the individual surfaces (as many surfaces as desired) and ChangeDegree to desired degree to change the degree 1 surfaces to higher degree surfaces
OR
Select the individual surfaces (as many surfaces as desired) and Rebuild to desired degree with desired number of control points

6

COOOL!

I’m going to try this workflow, thanks David.