Hello Michael and everybody,

I'm working on this particular problem of surface continuity. And I think I'm pretty close to achieving a continuous surface with MoI only. There are obviously some things missing with the outcome that I cannot figure out yet.


Here I started with 4 curves:




Network and Sweep produces 2 different results. Both are not continuous, I guess due to the sharp curve on top:




With the Network result, I extracted the middle curve:




I lofted the 2 side curves with the middle one. With the top edge of the lofted surface, I did Network with the same side edges, and the original bottom one:




I trimmed this networked surface with the original top sharp curve, to retain the profile shape:




The final surface is continuous, but 2 problems remains: The top edges are wavy, which deviates quite much from the original straight edges; And it's a trimmed surface, so isocurves are not natural:





I'm wondering what can be done to retain both the profile shape and the top straight edges. I believe this could be solved more deftly, but for now I'm kind of stuck. Maybe someone could shed a light on this.

Sorry guys I forgot to attach the 3dm file.

Hi

> Network and Sweep produces 2 different results. Both are not continuous, I guess due to the sharp curve on top:

Right, yes that's to be expected - if you use a surface construction method and give it a curve with a sharp corner in it, that sharp corner is going to be inherited into the constructed surfaces.

The main way to avoid that is to do what you show and have a larger smooth surface with the sharp corner borders coming from a trimming boundary instead of being a direct part of the underlying surface.


> And it's a trimmed surface, so isocurves are not natural:

Ok, but why is that a problem? It's normal for many areas of a model to be made of trimmed surfaces.

In something like this where you want a smooth surface with an irregular boundary a trimmed surface is what you want.

Also It can tend to be helpful to work with the neighboring surfaces at the same time, instead of just one surface in isolation like you've been doing here.

Then you can make trims from things like 2 extended surfaces intersecting against each other.

- Michael

Hi tuananhnp, I've been trying a couple of different ideas but it's pretty difficult in general to combine sharp, smooth, flat, and curved all in different regions of the same patch.

The XNurbs plug-in for Rhino might be a good match for this.

- Michael

Hi Michael,

The robust & intuitive nature of MoI always yields some urge and curiosity in me to explore workarounds for problems like this. I often think: "What if I can do them all in MoI, even if it's time-consuming?". But I guess I was trying to do the impossible here. Just want to let you know how much I love MoI.

Maybe for now I should avoid constructing these kinds of curve combination from the first place, if I'm determined to use MoI exclusively.

XNURBS looks very promising, but it's quite expensive.

Thank you very much!
I really appreciate your help and suggestions.

Hi tuananhnp, here's the best that I've been able to come up with while keeping all the outer boundaries constrained.

This one is doing the regular Network over the whole thing initially, then trimming out a "dart" type hole and putting in a blend to fill it.

- Michael

That's a pretty good solution!




Although it still shows discontinuity at the top & bottom part of the "dart":





Thank you, Michael.

If you can tolerate the bottom deviating from the original curve by some small amount (like 0.02 units) then you could do the cut like this instead and the bottom part should be smoother.

Getting the top to be smoother is probably going to be harder, the base surfaces have different surface normals at the point that they touch.

- Michael

Do you know a free Zebra Analysing Surface online ?

A trick that can be made! ;)

Hi Pilou,
blender as 2 zebra shading options in Matcap.
Here's an example.
Cheers
Barry

Thx but it's not on line! ;)
There is another one inside Free DesignSpark Mechanical! ;) (A SpaceClaim light)
but it's some tricky! ;) and also not online! :( https://www.rs-online.com/designspark/mechanical-download-and-installation
Import your Step Moi File - draw anything a sphere for example
Call the Arborescence - Lock the Sphere - You can manipulate and edit your moi File! ;)


Here i keep the sphere but can erase it and change the color of the cube! ;)
It's also here a PDF3D exported and created inside Design Spark Mechanical! ;)