Simplify surface


I need some help (or some fresh thinking to boost my tired brain…). I’m doing some minor adjustments on the surfaces seen on the attached screenshot. The object to the right is the starting point and the one to the left is the work-in-progress-piece.

I had to adjust some angles and raise some of the top surfaces and therefore I had do extend the marked (yellow) surfaces slightly. You can see the isocurves close to the top where the extension started.

It all works fine, and some new surfaces are created but the problem is the corner surface which ends up way to complex now (in this test created with networksrf and has millions of isocurves) What am I doing wrong here - why can’t I acheive a surface as simple and nice as in the version to the right? How would you create that surface?

rhino_dump.3dm (403.4 KB)


I re-trimmed edge 1 with a blend curve between A and B.
Created a surface with BlendSrf between C and D with Curvature and adjusted the two edges to be as close as possible to 1 and 2.
MatchSrf the new surface with 1 and 2.
rhino_dump-Marc.3dm (278.1 KB)

@pascal This is a good example where it’s difficult to get nice and simple surfaces with continuity as good as with Alias (from where to geometry comes from, it seems).

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Nice one - it looks good, thank you! I’m using MatchSrf way to seldom so it was out of my thinking here. @pascal And yes, the surfaces are from Alias originally and Rhino seems to have a more complicated view of things…

@Hoffster, @Marc, I did this:

Untrim at the edges Marc has as C and D.
Loft between these edges - simple surface.
MatchSrf to these edges for Tangency, Preserve other end as tangency, Isocurve direction automatic.
MacthSrf the other two edges (Marc’s 1 and 2) for Tangency, Match by closest points, Preserve Isocurve direction.

Matching for curvature should clean up more as well of course.

Does that seems reasonable? I know that what you want is a ‘Square’ tool with continuity built in on all four edges… so do I…


Yeah, it makes sense! But I’ll get problems joining these surfaces then, right? Ah, the square tool…! :smile:

Yeah- I set the U degree to 7 and then matched the shorter edges- that seemed to give enough control. Degree 5 and Inserting a knot or two might be enough as well.


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Look at that! Like a glove - thanks!

Oh yes! This has been mentioned many times… Any chance we’ll get such a much needed tool (soon)? :wink:


Speaking about that… I have a similar situation again!

I’ve been using your suggested strategy quite a lot lately, Pascal, and it’s been helping me a lot!

But I can’t really nail this one:

I’m having a hard time to get 4x smooth transitions on this selected surface. I’ve been trying to trim and sweep surface 1 and 2 differently in order to get the selected surface OK, but never achieved a satisfying result. Any ideas?

rhino_dump.3dm (307.2 KB)


Hi Hoffster - I don’t know if this is good enough - I can’t mess with it much this morning I’m afraid.

rhino_dump (1)_PG.3dm (345.3 KB)


I just used edgesrf on the four edges. Start with the big one at the bottom, then choose the two sides, then the top crv. Worked ‘perfectly’

rhino_dump-1ck.3dm (205.5 KB)

Hi ChrisK,

Thank you for your input! Yeah, it works but you’re not getting smooth transitions with this:

Thanks! The surface itself looks nice, but there are still no perfect transition between the surface and surface 1,2 and the flat front surface.

Surface 1 and 2 could be adjusted slightly - would it help to recreate them in another way?


Here’s my try…
rhino_dump-Marc.3dm (352.7 KB)

-I matched the surface D to C and E, it was a little bit off.
-I created a BlendSrf with rails 1 and 2-3-4m adding shapes between 2-3 and 3-4 then adjusting the handles at edge 5 (both in orientation using ALT and in amplitude by moving the points) so it’s as close as possible to 5.
-With it’s control points shown (F10), the new surface had a small problem from some bad influence of surface C. Using MoveUVN, I selected the two points that were badly positioned and moved the Smooth U cursor until they looked nice.
-I then matched the new surface to edge 5.


Brute force with a few iteration rounds of matchsrf between adjoining surfaces. :wink:

Hi Marc, I like your display mode, can you share that, or is it part of a package?

Here it is. It’s based on a map from Auxpecker.
Shaded_Mono2.ini (11.6 KB)


Thanks Marc!

Hi Marc,

Just a quick update:

I had to change some other details in the surrounding surfaces but I later on used your approach with some modifications and it worked pretty good actually! Thank you very much for your input! I also like your display mode - I’ll download your map!

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Hi again! I keep feeding this thread with similar situations… :flushed:

I have a symmetric object, see pics below, and I’m happy with all transactions but I cannot really manage to create a simple and smooth transaction between the last surfaces (the gap in the pic)

I always end up with one edge that doesn´t really match. I´ve been, among others, using all the approaches mentioned above, but never really happy with the result. Any creative ideas around this lovely saturday? :blush:

rhinodump_hoffster.3dm (440.6 KB)