Modelling a corner; smooth transition

Hello, Rhino community.

I have troubles with modelling this footrest pillow.
Two main questions are:

  1. I am adding more precise parametric curves to build a surfaces which attaches to other surface but still receive this crease between them. Surface must flow through those parametric curves on perimeter and inner curves (ISO-curves?).
  2. I am also adding more precise curves to describe corner surface but it is still has folds and creases and not that smooth as I want. Or maybe I am not thinking about correct topology/surfaces assembly.

Link to Rhino file: it is almost empty file but weights 10Mb -_-

In NURBS modeling “Less is More”:
less curve means more smoothness the result.

Try to not use inside curve and, picking just the 3 boundaries, choose the “Srf from 2,3,4 edges”.
This tool make a very clean srf but not continuos.
Next, using the Match tools, with MultipleMatch options, you can get the result you are looking for.

Attention: try to put the singularity, where the isocurves converge, on the top part of your model, this would help in getting better result.


1 Like

Hi, skysurfer.

I tried to run through your advices and I can’t get better results. I think I didn’t understood you right.
Also, “Srf from 2, 3, 4 edges” gave me vary bad result on the corner.
On the edge surfaces I can’t use this command because the middle curve must describe the surface precisely.

Some visual help would be great :smile:
Thank you for reply.

Hi try this way:

  1. copy cross section curve from position (1) to position (2).
  2. extend your rail curve (3)
  3. use Sweep2 or NetworkSrf
  4. cut with a curve or surface the bottom part that you don’t need

Hi, violine.

This doesn’t work well because I need yellow curve here to describe the corner.
Doing it your way - this curve and created surface don’t even intersect. So I can’t cut it away.

I’m sorry that did not help, try to work a little on that corner that has a sharp shape. Try also Patch command. Good luck!

Have a look at the tutorials in the Level II Training Guide.
Exercise 18 - Soft corners

Try to make surface(s) that have four edges… I only did one corner, you can try the rest…

Model Test.3dm (120.3 KB)


Hi, John_Brock, where can I find these tutorials?

Hi, kevlism.

This is very nice result. But as I see you didn’t use middle curves to describe surfaces which is very important because it changes a shape.
Also exterior corner radius is quite big on your example which probably makes it easier to achieve this nice result.
I am creating a precise model for production. That’s why I should stick to all given curves.

But I also tried to do it the way, kevlism described and this is what I’ve got. Pretty sad.
When I do the routine - these are my steps to do it:

Rhino Web page - Support - documentation section.


The problem is your curves have too many control points that were not needed. Also, you should keep the same amount of CP counts in both U or V directions.



I’d troubleshoot and fix it this way…


Thank you Brian for this nice and useful tutorial.

Thank you, @BrianJ this tutorial is super great.
It definitely solves this problem. Also thank you for showing a problem with tolerance and that funky corner bump.
Is it called “class A surfaces”?

@kevlism, unfortunately I couldn’t reach your link.
But you might be right about control points. But what else can I do if those parametric curves are reached by “Crv from 2 curves” or similar command? If I will rebuild it - it will not be that precise anymore.

@John_Brock, thank you. I downloaded this tutorial and will go through it.


I think you will just need Brain’s method.

@John_Brock, I went through this tutorial and couldn’t complete it in the end because the “_FilletEdge” command returned “Failure in building corners.” while trying to finish 15 mm radiuses.
I am not sure if this tutorial could help me to solve this issue. At least I don’t understand how.