7 WIP SUBD troubles converting from NURBS to Sub-D for specific edge adjustments

So I’m trying to do a very small edge raise along a precisely booleaned and filleted edge. I can’t massage a Sub-D object into the shape I need, and every time I try to make my NERBS into a Sub-D object, it explodes into a dozen strange shapes that have no similarities to what the original object was. Can someone tell me how to either properly transform my NERBS into Sub-D or, and preferably, tell me how to boolean a Sub-D model so I can cut the edge I need?


Well. We cannot see the model. Also, keep in mind SubD isn’t for everything. Sounds like if your design requires a Boolean then it is probably not meant to be modeled with SubD. Or you should do all the modeling that requires SubD first then convert to nurbs and do the Boolean parts.

1 Like

thanks for commenting so quick! I’ll upload some photos of the organic raised edge I’m trying to get on the right, and the rigid, uniform thickness I have on the left that needs to maintain form.

You can create another edge loop and then use creases.

Use the QuadRemesh feature

It’s called NURBS, please correct the title


Thanks to everyone who posted, I managed to figure out a solution to my problem! I took my NURBS model and made it into a mesh, before converting a mesh into a sub-d object. It needs a little finessing, but it worked (sub-d on the left, mesh in middle, NURBS on right)

. Thanks for the help!

What is the point of subD in that case? That topology is not good. Why do you need subD here? Look at @inju image. Nice topology and just crease edges that need to be sharp (in red).

the point is that the ridge isn’t supposed to be sharp. It’s supposed to be a natural, organic shape. While Inju’s example indeed has nice, clean, sharp topology, it’s missing a natural flow from smooth surface to raised edge. While my topology needs to be cleaned up, once I do so it’ll have a smooth and natural transition that Sub-D allows for. I’ve added an image that includes a NURBS based version, and illustrates my point as to why it’s not what I need. The environment mapping shows a distinct crease line on the lower portion of the ridge and it makes it look incredibly artificial, even if it comes out with nice topology without a half-hour of adjustments. If someone could tell me how to smooth out the bottom of the ridge (Inju, I apologize if that’s what you were telling me in your example and I just haven’t understood yet), that would solve me having to do a bunch of editing to the topology of the Sub-D surface versions. Also, please go easy on me, I’m totally self taught so I don’t understand some of the terminology used sometimes!

I think you don’t understand the transformation of NURBS into SubD.
Transformation should be like a mirror copy, if you have NURBS smooth, then SubD should be such, if you have a NURBS model with sharp edges, then SubD should be with sharp edges.

In your case of transformation through Mesh, the result in SubD is not at all similar to the original NURBS. I think you can see it for yourself.

Just use the QuadRemesh command. I’m not an experienced user of SubD and Rhino 7 WIP.
If you want to get the right answer and quickly, you need to upload your model here.
I don’t speak English.

The typical workflow in that case would not be to go from nurbs to mesh to subD, as you see it makes a bad topology. Since your model seems to have trims the best workflow would probably be to go to subD, remove the creases, then stack the edge loops. Nurbs is usually the last stop, not the first and if you have trims, going to mesh as you see gets you triangle junk on the edges (although you could quad remesh).

For the edge condition, the typical workflow if you want the flow to go around the edges rather than crease is to stack the edge loops. The more edge loops you add, the tighter the edge condition will be.

1 Like

Example QuadRemesh command.

example how to draw folds, or reverse how to smooth.

1 Like

Exactly! Good ol’ edge loop stacking.

1 Like

Thank you Inju and Michael! The quad remesh command was exactly what I needed, I just needed to futz around with it more, and the other example videos the two of you gave me will help simplify my workflow immensely!

Seriously, thanks a bunch! Hope you have a wonderful day! :smile:

Non Uniform Rational B-Splines ie NURBS