Surfacing... just a nightmare

isn’t that 5/6th place in your picture? It surprises me that you need such tight tolerances, it seems a bit too much precision asked? In fact I have never felt any reason to go beyond 0.001 mm tolerances. Why do you need it to be so tight?

Well, to get 3/4th accuracy when projecting curves, you need 5/6th. The problem is that you cannot select accuracy on a per operation basis… as far as i know.

If I relax the tollerance, then tangency calcuations cause problems at 1/2 dec places. That ripples through the project causing more issues

The tight tolerance of .00001 is probably causing more problems then it is eliminating. To Join curves the ends must be within the tolerance of each other. So if the tolerance is set to .00001 the ends have to be much closer than if set to .001.

@Proterio Are you routinely looking at numerical coordinates to judge if the results of commands are satisfactory?

can you post a simple example where this happens?

As far as I know, there is no such thing as a magic NURBS tool that solves everything with a few mouse clicks. Every shape requires different strategy that ultimately may lead to trying multiple approaches until the end result is satisfying. I recommend following the Rhino tutorials (accessible with the F1 key) and trying to understand what purpose every tool has.

For example, here is a single surface that took me about couple of hours to create about 10 years ago. Rhino’s “Blend surface” tool didn’t gave the best quality, so I had to fix it with the help of a few other tools. The process included simplifying the surface, followed by slow and tedious manual adjustment of individual control points, and some use of “Match surface” and “Insert knot” at certain steps.
I can’t share the 3d file, but I still keep the stages of improving that surface in separate layers and can at least show the required steps to achieve the final result:

There are two bad areas that I failed to spot at the time. Look at the bottom inner corners of the surface where two control points get too close to each other. I had to move the 2nd control point higher, but I guess it’s too late to do that. :slight_smile: Judging by the position of the control points, I assume that it was the result of using “Match surface” with G0 (position) on the inner surface edge, but seems like I forgot to use the “Match edges by closest points” option during that command.

0,001 mm precision was used for the Move UVN tool at this step, because every tiny change affects the Zebra and Curvature analysis by a lot.


Are you routinely looking at numerical coordinates to judge if the results of commands are satisfactory?

Only when operations fail )

slow and tedious manual adjustment of individual control points, and some use of “Match surface” and “Insert knot” at certain steps.

Wow that is a lot of noodling. This process sounds like a black art. I was hoping to be able to get decent surfaces without that, or at least surfaces that match along seams.

Sadly, Rhino lacks a static Zebra analysis, which could speed-up the fine adjustment by a lot.

My favourite part of the VSR plug-in for Rhino 5 was the extremely good coloured stripes of the Light lines analysis that it introduced. Their colours were cleverly selected and definitely do a better job than the similar analysis tool in Alias.

Hi -

Have you tried the GHGL test that was posted here:

I’ve now made sure that this feature request is on the list of things to track - RH-58682

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I don’t have any idea how to use it :smiley:

I could not agree more. I think NetworkSrf, like Patch should be used almost never. NetworkSrf should literally never be used to make primary surfaces. Ever.


Oh dear god…Steve1 is that you?

Steve1 is that you?

Thats only 10th of mm in the real world.

To clarify, I am calculating Tangency without iteration, so its an approximation. Using 5dec places results in accuracy to about 3.


When I loosen that to .00001 it results in 1


There are no tools available for doing this in Rhino or GH.

many of the smaller ones do- and many of the larger ones do yet don’t talk about it… :wink:

Okay let me explain the Steve1 reference, because it’s actually informative. A few years back, a fella by the name of Steve1 came on here looking for help making models. His project was super duper secret (obviously making WWII models, likely for making scale models, but like shhhhhhhh!). We tried to help Steve1, we really truly did, lots of us. He was struggling with the absolute basics - getting things watertight, patch layout, lots of general “how do I make this?” questions, which almost always involved for him feeding a giant rats nest of curves into NetworkSrf. He seemed to have lots of preconceived notions about how freeform surface modeling SHOULD work, and then ranted about how things didn’t work the way he thought they should, while clearly not ever understanding how things ACTUALLY do work.

You’re not doing yourself any favors by being all cagey about what you are actually trying to model. If you want help from the general community, start with “hey guys, this is the shape I’m trying to model.” You will get far more instructive answers, and people can likely steer you in more productive directions. This whole “let me show you this ultra close up of two edges that aren’t watertight” doesn’t actually help anyone help you - to help you solve that problem, people need to understand the greater context of the surfaces around that naked edge. If that model is somehow under NDA and you can’t show it, but you’re struggling with issues like simply making your model watertight, well, god help you and Steve1.

Don’t be Steve1. If you want help modeling something, start at square one. “Hey guys, I’m trying to model this type of shape:” The first thing that you need to consider on ANY model is patch layout. Literally, that’s square one. If you’re not showing your overall model, no one can check your patch layout. Everything that you post seems to indicate that you are in way over your head, so if I had to guess then I’m betting many of your problems start at square one - patch layout. You’re answering questions by zooming in on minutiae, which is helping no one, least of all you.

Seriously, this is so Steve1…


What have I done wrong this time?
Poor me, always at the gallows … :zipper_mouth_face: :no_mouth: :upside_down_face:

I would lie if I would say it didn’t cross my mind too.
Might say more about us than about Proterio though…

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Im dont want help modeling, and I dont want my patch layout checked thankyou. I had my physical recently ) … If you are interested in solving specific problems, I have posted 2 so far, Tangency & Split that remain unsolved.

I understand where you are coming from. My project isnt super secret. Some of the people replying to this thread know all about it. I also understand that Engineers just want to tear into the specifics of the project and solve it. If you want a shape, picture a bathtub, yes seriously, and the problem of calculating how much water it holds. That should not be this difficult.

As i said thats like giving me a fish. I eat for ONE day. I am asking more general questions in this thread so I can learn to fish. I have had to defend why I am using a tight tolerance, and why my curves dont line up. I did. I am capable of modelling this once I grasp whats required to make surfaces match.

Diving into this specific challenge is just going to change the focus to the specifics of the model. There are many threads that do that. This one is a more general discussion, with your permission )

I am willing to bet many people have faced these challeneges modelling. In my discussions with people they all they say the same thing - practice for 6mo then you will “get it”. Most are not willing to be this pushy and procative. I do so to expand knowledge for more than just myself.

I have watched a lot of videos, read a lot, hired experts - some that posted in this thread, worked on this for months and STILL surfacing results I desire elude me. Is this a problem with me failing in the ways you suggest, or is it that surfacing needs a LOT more discussion from a first principals perspective?

I am not sure what you kmean by patch layout. Perhaps you could post a link to a video or thread… that way those that follow can benefit also.

As for being way in over my head, Ill ignore the condescension and remind you that all experts started where I am. I get that this thread is irritating to you, but some surprising and illuminating answers are emerging.

To use your fishing analogy - you’re not fishing, and you’re not making it any easier for anyone to teach you how to fish. You’ve disassembled your reel and you’re staring at all the internals under a microscope and then wondering why no fish have jumped into your boat. I know you think I’m being condescending, but I, and lots of other people on here are trying to teach you how to fish, not simply giving you fish.

You’re really making my point for me here. I started where you did. So did many other people on this thread. I haven’t lost sight of that, but I’m telling you, straight up, you’re making it impossible for people to ACTUALLY teach you how to fish. Start with “This is what I’m trying to model” not calculating tangency to five decimal places.


OK enough with the Holier than thou criticism. I got your point. Post some links or move on. Thx

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If you’ve gone through the Level 1 and Level 2 course material provided by McNeel, then the first ~150 pages of that tutorial is the best thing out there to show you how think like a surface modeler.