# Grasshopper + SubD

A ship designer (called Proterio) combines Grasshopper with NURBS: Surfacing... just a nightmare

It seems that combining Grasshopper with SubDs would be more efficient method of designing streamlined ships and airplanes.

Looking forward to a youttube tutorial or an example file to get me interested in investing time, energy and frustration exploring a new avenue

FYI I wasted months with TSplines to finally realize that it just was not going to work, so a brief explanation of how SubD is different /better would be most appreciated )

SubD = smooth, complex surface defined by few control points
few control points = simple Grasshopper program

I hear you. Would love to see a short YouTube vidâ€¦

The piece I am not able to visualize is how two smooth curves in vertical and horizontal planes respectively, can be modeled by a surface regardless of how many control points the surface is comprised of. Thats the horse following the cart.

Curves are the source of surfaces. To create a smooth sheer curve you need to combine two curves that comprise the sheer line. I seriously doubt it would be possible to accomplish that by moving control points on a surface without using the two curves as a guide, and many hours of tweaking. May as well just use the curves and create the surface.

What I could see a use for, is taking a number of surfaces that are joined to form a solid and replacing them with a single SubD surface somehow. Currently I am forced to extract isocurves and then loft them. Where there are challenging contour changes, GH is used to generate and order of magnitude more curves. Its crude but with a little tweaking works well enough for govt work.

" If youâ€™ve been a Rhino3d user for some time, then you may be familiar with plugins such as T-Splines and Clayoo. These brought a SubD workflow to Rhino but crucially, these were mesh based. So, the underlying geometry was a mesh which was smoothed to approximate a curvature continuous surface or poly-surface.

The new SubD objects in Rhino are spline based. So, just as with Rhino NURBS objects, they provide a continuous description of curve geometry. This means that SubD geometry can be created accurately in Rhino and this gets over one of the major criticisms of mesh based SubD workflows that are often regarded as being approximate."

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Rhinoâ€™s surface commands such as Loft, Revolve, Sweep 1 & 2 and Extrude all now produce direct SubD output.

Oooh that got my attentionâ€¦

So is a SubD surface intrinsically able to handle more complex shapes produced by curves that are not smooth in some of their transitions?

Or perhaps I should say, is a SubD surface going to be the same as a regular surface given the same input curves?

Yes it should be, but as degree 3. SubDâ€™s are degree 3.

features of subD surface Catmull -Clark:

And all SubD functionality is available in GH modules?

Rhino SubD is not the same

In Gh no, Not yet.

OK. Please let me know when it is implemented in GH. I only use Rhino as a display port now. For me, it is pointless to model with mouse clicks in Rhino

Well. You could use Rhino WIP, then you will know yourself when it is there . There is some SubD stuff already.

It is very tempting to go down that rabbit hole, but I must focus on design WITH the tools not the tools themselves )
There are many challenges. I started a thread about the surfacing challenges and my frustrations and unrealistic expectations, but this is only one. Structural analysis of any kind from first principals is a pragmatic nightmare that can only approximately be modeled with simplistic tools at present. That curve is even steeper than surfacing, but perhaps more important for design work, and the rabbit hole that precludes WIP adventuring at present.
I very much appreciate the efforts that all of you make to improve this product and recognize that much of it is a labor of love. It has not gone unnoticed!

It seems that SubD cannot convert a trimmed Nurbs surface at present. That is surprising given the definition. Will this change in the future perhaps?

Unlike a car body, a boat hull is a continuous surface that must be watertight. It is comprised of many surfaces some of which, inevitably are trimmed.

For various reasons, the entire hull (or half hull) needs to be represented by a SINGLE surface. Currently the only way I have found to do this, is to use GH to create a series of curves in varying densities, and lofting them. While not perfect, the result is workable. The biggest challenge is a crease that fades out very smoothly.

IMO SubD needs to be able to rise to that challenge .