SubD - Local Face Division

Just checking for update here on RH6 SubD commands, has Subdivide been updated to apply to local faces yet or does it still only apply to the entire SubD element?

All the new subd work will be in the Rhino 7 WIP available here Welcome to Serengeti. There’s a new command called SubdivideFace that currently only works on meshes but will be hooked up for subd faces as well. You can use ExtractControlPolygon to get the mesh from a subd to use it and then ToSubd to convert again.

Thanks Brian.

Hi Brian, do you think the new Subd commands would allow to do this?

Working on a single mesh (non-closed volume) and toggling very inter-actively between mesh / Subd would be great. I’m such a RH/GH addict I don’t ever want to leave it.

Hi Alban,

Using the PointsOn command or F10 will display the control point cage for a subd surface now. You can also sub-object select subd faces, edges and points. The ctrl pt cage is like the base mesh you would use a subdivision modifier on in a polygonal modeler like in the vid. The mesh tools used such as inserting edge loops etc. are features being added to the WIP with the goal being that they work directly on the subd surface. One difference you’ll find with subd in Rhino versus a poly modeler modifier is that there aren’t levels of detail to choose from for the smoothness. The smoothest result is created as a spline surface rather than a subdivided mesh.

Please post any suggestions or wish items in their own thread if you feel like there’s something needed in the WIP. Here’s everything tagged for subd in our system visible to all users if you want to browse through. Thanks!

I’m also waiting for a simple split face tool for SubD, as it is already for surfaces. It is very common in low-poly modelling. Thank you!

Hi @Bogdan_Chipara
I think you might be looking for InsertPoint (which is a really bad name for that command, I think!)
HTH, Jakob

Hi @Normand,
No, I’m not looking for Insert point, I know that one. I just need a simple Split-face tool. with snap on perpendicular, midpoint etc. I’m sure everyone knows it from Maya, Blender, etc…

Hi @Bogdan_Chipara - You can achieve this with InsertPoint. It pays attention to Osnaps. You do have to click twice though to split the SubD face, but it’s the same for SplitFace. Is there a different method you’re after?

Hi @Bogdan_Chipara
I’m probably in over my head here, but I don’t think it’s possible with Rhino’s implementation of SubD - there is no T-intersections, as T-splines had it (since AD now owns those patents, I guess). Also, since the underlying topology is a mesh, for now Rhino has no concept of mid, perp, tangent etc.; only edges, faces and vertices. You can cheat on the mid snap, by using SmartTrack to select the two vertices in question - then it will be able to detect the mid point. If you look at your SubD object in box mode, you’ll see that InsertPoint does exactly what SplitFace does. It’s true that it will look different in smooth SubD mode, but that’s the way SubD works.
HTH, Jakob
EDIT: Ooops, wrong about the mid snap… that works fine, but no perp snap.

Hi @Vanessa, I don’t mind clicking twice. But I do mind that it doesn’t take perpendicular snap and I don’t have a preview guide for the new edge.

@Normand, I see snapping working well for midpoint and near. but not for perpendicular.

Yea, I just realised that as well - my bad!

@Bogdan_Chipara @Normand - Yeap, I just saw that too. Added to the pile (RH-58502).


omg InsertPoint is exactly what I have been trying to find to add in an edge, why is this command so badly named? I never would have guessed this is how to add an edge into the low poly view of Sub-D.

I want to split this sub-D face

Like this:

InsertPoint will not work because I can only select other vertices. If I use subdivide with that face selected I get this poor result:

Why would this not subdivide the way I want the faces to be? That is perfectly in 4 (subdivided by 2 half on both sides)?
How else could I acheive my intended result?

I am a parametric modeller (SolidWorks) with proficiency in Rhino currently trying to master polygonal modelling/sub-D NURBS in Blender and Rhino.

Ignore me, I just realised I can do it by adding two edges in a row in order like this;

Still curious why subdivide wouldn’t do this though.

Because the subdivide command runs one Catmull-Clark subdivision step. Roughly speaking, that means add a vertex at the center of every face, and a vertex in the middle of every edge, then connect these with new edges.

Your face has 8 edges so that means 9 new vertices and 8 new edges. It looks like a quad face in the flat display mode, because of the aligned edges, but it’s not. The smooth display mode (maybe with control points on) might show more clearly what is going on.

But you can’t use the InsertPoint command in smooth mode, it reverts to lowpoly presentation when you start the command.

For what I intended to do there, is there or could there be a command that would have done what I intended to do in one operation?

It should switch back to smooth after exiting the command. Anyway, switching between smooth and flat display modes in SubD does not change what the surface is (for example, meshing it gives the same result in both display modes), only what is being displayed (smooth shows the limit surface, i.e. the actual shape, flat shows its control polygon). I was suggesting switching to smooth display to clearly see the 8 edges of your face, since you seemed to expect it to subdivide like a quad face (4 edges) instead.

Not that I know of.