Zebra analysis problem and Math surface question

Hi dears :smile:
i have a problem with zebra analysis and a question about match surface:

Problem with zebra analysis

In zebra analysis usually i have problem to distinguish curvature(G2) from tangency(G1) as you see in the pictures

curvature continuity(G2)

Tangency continuity(G1)

What should i do?

Match surface question

As you see in the picture :

I want to match surface number 1 with surface number :
At first i match surfaces 1&2(G2)then if i want to match surfaces 1&3(G1) my match between 1&2 surely destroy ? or have change type of continuity (for example G2 transform to G1)?


rhino_basics.pdf (2.5 MB)
Surface Continuity (Part One).pdf (122.1 KB)
Surface Continuity (Part Two).pdf (130.5 KB)

And this. You can DL from grasshopper website.


My suggestion is starting from basic model… The only thing you can benefit from “following from the book” is gaining a lot of patience…


thanks for your attention dear Kevjin

Hi Shayan- If surfaces (e.g.1 &2 in your image) are mirrored copies, matching for tangency and ‘average’ set will get you a very good G2(Curvature) match with minimal changes to the input surfaces.


1 Like

Hi dear pascal
I sent the surfaces before matching

rhino.3dm (297.1 KB)

It appears you have an illegal copy of Rhino. I’d suggest fixing that first before you fix your geometry.

1 Like
  • There is a bug needs to be fixed… That is-- Zebra shows wrong continuity feedback.

For now, you can join two surfaces. Not always solve the problem, but did you try?

Hi KenJin- why do you think this? Shayan, can you send the surfaces, before any matching?


If I had to guess, I’d say majority of those who ask elementary questions here are using pirated software. In case of those using Matrix or other hyper expensive plugins, I’d say the pirate percentage goes upwards of 95%. Surely, someone must be buying those software for the companies to stay afloat, but whenever contractors or students send me files with such identifiable data in them, I automatically tell them that they are using pirated software and that I won’t deal with them. None of them have ever protested.

I wish McNeel employed an authentication mechanism so that in addition to providing free software to pirates, they did not provide free tech support as well. It takes focus away from the needs of legitimate users.


I PMed you.

I think Mcneel should take a look how V-ray does. Without USB, I can’t use it. That is a fresh idea.

Hi dear Kevjin
I joined them but didn’t result

That is an utterly unfounded statement, in any evidence that I know of. I wonder what on earth leads you to such a statement. Many beginners ask questions here and we welcome and encourage them to do so, The forum is for novices at least as much as for experienced users.


1 Like

If you look at Zebra before any matching you’ll see the surfaces are very nearly G2 already - in other words the third row of points is already nicely positioned… Matching for tangency cleans up the first two rows. I do not see a problem here… ?


Dongles don’t prevent piracy. Many of our students have a cracked V-Ray… Very few buy it (mostly because of their bad license policy.) --Mitch

1 Like

you mean:
because of the surfaces are very nearly G2 already it isn’t possible to see the sharpness with zebra even nicely mesh setting?

What sharpness?


the difference between tangency and curvature continuity in zebra analysis

kinks or jump sideways as they cross the connection from one surface to the next

I assume that you know how virtually different between G1 G2 on Zebra.

  • You cannot make G1 to G2 by simply adjusting mesh settings.
  • “Look close” term only uses in G2 or above continuity. That’s because you cannot or extremely hard to distinguish G2 and above curvature continuity by simply looking at Zebra or curvature graphs.

You might ask for your brother in Italy get a Rhinoceros. In that case, the God might help you.