Complex surface transitions

Hello everybody :slight_smile:

I have a complex surface transition for which I’m unable to find a solution after a lot of trying.
This is what I was able to accomplish and how it should look like in the final shape.

But, as you can see it’s a mess. I tried to build surfaces with the same degree to match each other but in the end, I wasn’t able to have a curvature continuity between all the surfaces, not even a tangency continuity in some cases.

This is the topology:

I tried to pump up the degree of the surfaces to be able to match them and in some cases, it worked.
And these are the primary surfaces I used to start.

I watched the great series tutorial from an expert user of this forum about the surface modeling: Better Living Through CNC - YouTube
But still, for this particular transition, I’m not able to build the surfaces properly.

Do you have some suggestions on how to build this shape with continuity? I think I’m doing something wrong from the start.

Here the rhino file (v5 and v6) with the primary surfaces and my final surfaces.
RhinoForum_v6.3dm (1.4 MB)
RhinoForum_v5.3dm (1.4 MB)

Thanks to everyone who will help me :slight_smile:

Hello - it seems to me I’d keep these surfaces linear

and match all the others to them. Also make sure you adjust your Zebra (Analysis mesh) mesh to be very fine - 5,000 + in the ‘Minimum grid quads’ setting.

Something like this, perhaps - RhinoForum_v6_maybe.3dm (431.9 KB)


Here’s a possible option. built everyting to theoretical sharps and after this trimmed back. These may not be the exact aesthetic you are going for, but by adjusting the size of the blends you can tweak ti to your liking.

Test_Blend.3dm (2.0 MB)

Hello Pascal,

Thanks for your reply, unfortunately, I don’t have rhino v7 and I can’t open what you sent, if you could save it as rhino v6 I’ll be thankful.
Anyway, I started with the surfaces you’re referring to as linear but matching with the adjacent surfaces changed them like this. The main problem with all of these surfaces is that I can’t match all of them together. Multiple matches don’t work and if I match one edge the other edges are messed up. It works with just one edge and all the others will mess up.
But I’ll try again starting from there as you suggested. Thanks

Right - I think I’d make sure to match to these surfaces, but not match them to the others.

RhinoForum_v6_maybe.3dm (434.6 KB)
V6 this time…


Hello Mark,
Thanks for your reply but you said correctly, it doesn’t work for the aesthetic I am looking for. Or at least, I’m not able to make it work, because I already tried something similar. If I change the size of the blends it will change in all the blends with the upper surface. The problem is that I have different radiuses of the blend so I have to use a different method.

I can’t’ have a unique blend with the top part (using just the green surfaces). I have a bigger radius in the internal part, so I added more surfaces (the red one) trying to make it work.

You can still use the same techique. I used a simply 0.2mm offset to create the outside rounds, but you could use a tapered pipe instead to get the transitions you need. This will allow you to control the width of the opening between the theoretical sharps.

If you can get the model to look good with theoretical sharps the blends will always turn out well. Based on my experience it’s nearly impossible to get good blends if you are simply guessing the openings of the blends. I know these can be quite tricky to model, hope you will find a good solution.

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I followed the suggestion from Pascal and rebuilt everything, matching to the linear surfaces. In the end, this was the result. I still have some issues with the matching of some of the surfaces but it’s much better now. It was even difficult to visually spot these problems with zebra because they are visible in a few angles.

I think it looks ok but it can be better.

Here the rhino files if someone knows how to improve it:
Issues_v6.3dm (16.9 MB)
Issues_v5.3dm (16.9 MB)

Anyway, someone knows where I can find tutorials of advanced surface modeling to learn better? It’s hard to find a good one like the one from @sgreenawalt (thanks a lot man!)
Thanks and have a nice day

Thanks for the advice Mark :slight_smile:

If you can get the model to look good with theoretical sharps the blends will always turn out well. Based on my experience it’s nearly impossible to get good blends if you are simply guessing the openings of the blends. I know these can be quite tricky to model, hope you will find a good solution.

You’re absolutely right about the theoretical edges but I didn’t understand how to apply it in this particular case. If I do a tapered pipe to trim the upper edge it’s ok, but I have two other edges to blend with. How should I do what you said?

Sorry if it’s a stupid question but I’m just starting out to understand how surface modeling works. I discovered recently, thanks to the Sky’s tutorial, that until now I did everything in not a good fashion :S

General rules of thumb for blending/filletting is to start with the biggest radii and work to smaller ones. In this case, from what I can tell is that the vertical blends/fillets are bigger than the final one that runs along the top flat surface.

The way I did this is to build all the vertical blends/fillets first and the smallest on along the top surface last. Does that make sense?

@FFstudio - I would simplify this surface:


The more points, the harder it becomes to keep things under control, especially at high degrees - if you are increasing the degree to get more points, I would be careful of doing that beyond degree 5, rather, InsertKnot > Midpoints =Yes. But I do not think you need that here.
Simpler.3dm (43.0 KB)


Been so busy with work the past few months, but I’ll do a vid on this later this week, there’s lots of good teachable things with this one, really ties in a bunch of the concepts for the basic series.



Made a little vid, focusing on patch layout and workflow, I hope folks find it helpful!

ComplexTransitions_SG.3dm (467.8 KB)


Hello sgreenawald,
thank you very much for the clean execution! I’ve been working this way for a long time and save a lot of trouble!
Greetings from Chris

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Hello Sky,
Thanks so much for the video you made. Very helpful! It seems so simple made it from you :joy:
Anyway, I need a bigger blend between the first surfaces you made, when I’ll have a bit of time I’ll try to model it again from scratch using your workflow and technique.
Thanks again, I really appreciate it and can’t wait to see the tutorials you pre-announced!!

I am still waiting for the rest of your genius mini tutorials , very efficient , and super clear ! thx a lot :grinning: