SubD - inherent characteristic or poor approach?

I’m hitting a problem trying to model accurately the leather skin of an old camera in SubD. It’s basically a box with rounded ends and various indentations and cut-outs:

I have used quite a lot of segments for the rounded ends and succeeded in getting accurate circles. However, after making the cut-out for the camera back (the bigger one), with creased edges for the opening, the shorter edge of the hole pops out slightly and I get a small but nasty artefact around the corner:

The vert at the outer edge of the case has not popped up, so I’m assuming that the problem behaviour arises from having the opening:

Is this an inherent weakness of SubD, or is there anything that can be done to avoid it?

Camera Skin - SubD issue.3dm (1.3 MB)


p.s. I can make the shape illustrated with NURBS, and have done so, but some of the trickier modelling yet to come is better handled in SubD.

Just a couple of observation.
If the edge loop at the problem corner would go around instead of looping into other parts of the geometry… it may help, at least it will let you add another edge to smooth the transition from crease to no crease [if you crease that one edge the nasty blimp is gone [but you have a crease where you don’t want it]

  1. there are also issue in another part of the case


Hi Jeremy - I don’t know how this fits with your plans but if you can bevel that corner and then remove the creases, it starts to look better:

(I think bevel at two segments looked better than the three here)


1 Like

Thanks, I’ll check that out.

I appreciate the suggestion about the edge loop. I guess I need to spend some time thinking about how things like that come together.


Unfortunately I don’t have a lot of scope for bevelling this as I’m trying to reproduce a real object which, selfishly, has nice square corners. :frowning:

I’m interested to know whether this is a fundamental limitation of SubD, a Use Case that hasn’t yet been catered for in the Rhino SubD development, or something that will work better with a different approach (e.g. @Akash’s suggestion).

On a wider note, I’m coming to the conclusion that making a model of a real item can actually be harder than designing something new.


fwiw, this shape is more suited to standard nurbs tools-

If it’s a learning project I get it, carry on… but if its a paying gig, I’d go straight nurbs here…

(and you know how much I looove subd. )

you just have to make sure when you get a shiny new hammer you don’t use it to pound in screws…

1 Like

the above said, one idea is, you can model it subd, but crease all the edges, and then convert to nurbs, then use fillets to make your transitions.

that way you get the speed of subd, and the control of nurbs…

Yeah, it was a deliberate decision to explore the potential of SubD within various aspects of this model as a learning project (and labour of love). And there are some organic cut-outs to come that I couldn’t readily achieve in Nurbs so this seemed like one of those opportunities… Actually, I shouldn’t really be doing any of this in Rhino - 3D-Coat would be Dr Who’s sonic screwdriver for these screws - but trying to push the limits occasionally is the best way of understanding where they are. And then I’ll probably do it all again in 3D-Coat just by way of comparison.


Footnote: “When all you got is a hammer” from Blackbirds album by Gretchen Peters - powerful song.

1 Like

I thought to try out a throwaway conversion before going any further: I got nurbs, but not very nice nurbs:

Versus hand modelled nurbs:

Agreeing with Kyle here that this is something that should be done in NURBs.

Adding a wrinkle: I often use NURBs for most of a part and use SubD to get started on more complex curved surfaces within a part, later converting to NURBs and joining with the part. In this case, though, this really looks like straight NURBs.

1 Like

Thanks Max I appreciate the thought, but as you might infer from the second screengrab in the preceding post, I have a nurbs version too… As I said to Kyle, I aim “to explore the potential of SubD within various aspects of this model as a learning project… …trying to push the limits occasionally is the best way of understanding where they are”.


Thanks to everyone who has contributed their ideas on what to do with this modelling. It’s the willingness of people to chip in with their ideas that makes this forum a very special place.

However, I’d still like to know if the vert popping up, and the artefact that goes with this event, which seem to be caused by the presence of a creased edge cut-out, is a fundamental behaviour of subd that cannot be prevented or just something that the subd devs haven’t got around to addressing yet.

typically speaking, a crease will have some difficulties to work thru. that’s why I typically crease early, then change them to a bevel once I have the early heavy lifting done.

I personally don’t like creases as they look “fake” in renderings… (real things typically don’t have perfectly sharp edges, seeing them is a dead giveaway for CGI)

BUT, I do use crease when I’m laying stuff out and want to keep track of what edges are going to be sharper than others.

1 Like