Hello, what is the best way to blend two surfaces in Grasshopper?
The screenshots show a Loft that is G0 and I’d like a seamless smooth G1 continuity.
I need Native Grasshopper components only. No GhPython, no C# scripting, no plugins.
The surfaces are always planar but some parameters will change the sections shapes (X and Z / not Y). The blend needs to adapt to parameters change “live”.
I’d be so grateful for your help. Thanks !
Please upload what you have got. The solution to get what you want depends on the geometry of the other parts. Regards, Eef
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Hello,
there is no proper way in doing this with native components.The biggest downside of Grasshopper is that it lacks fundamental surfacing tools or other advanced Rhino features.
Matching surfaces, especially of this complexity (high curvature, likely weighted, multispan, multiple edges), is very difficult to implement on your own. And even a good algorithm can fail in these cases.
You could try to patch it or utilise sub-d tools. But this will likely not work or fail to yield the expected quality.
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Thank you for your reply, I’m trying many different settings and I would not mind to change if I’m told one works best.
What I’ve now is two Breps, open sides on planar and facing, loops of the sections with seam aligned on max Z point (points top of the sections).
I don’t find a way to loft (blend) the surfaces (this is what I want). I only find ways to loft curves and it results a G0.
Thanks a lot Tom for this clarification. So far I only could use curves and didn’t find ways for the actual surfaces to loft or blend. I will try what you suggest (patch or sub-d tools) to see.
I’m thinking if working with surfaces directly is not possible, perhaps making some kind of handle curves to guide the curvature of the bridge?
Those surfaces don’t look planar to me. With rare exceptions, users who post no geometry can be (should be!) ignored.
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so, upload what you got. Internalise in a .gh file or uplaod the .3dm
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It seems that you are dealing with Brep and no surfaces
They seems native to me. I don’t understand this. Are you in a school ?
You want something quite complex with lots of constrains and without giving much.
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screenshots are indeed raising more question marks than explaining 
it looks like you have polysurfaces?
Posting your geometry (or even just a small part of it if it’s sensible content (like the trim in this picture) would benefit the discussion a lot
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I am not a professional Grasshopper user. I’m quite comfortable with Rhino, which I’ve used for years, but I’ve only been using Grasshopper for a short time. I am not even in school I learned Rhino by myself mostly through tutorial online. My only friend so far for Grasshopper is ChatGPT, and you’re my first Gh human contacts.
On top of that, I am not a native English speaker. I was wrong to use the word planar. What I meant is that both open faces of the volumes are cut along the Z axis, parallel to each other.
I’m a world-famous old-school craftsman who developed a new item mixing traditional craftsmanship and newly designed parts. That model is very successful today, and this is thanks to Rhino for the new parts.
The next level is a new idea, it’s very serious, and for this I need a basic structure made with Grasshopper. For now, everything works, but I’m stuck with two separate volumes that I need to blend without losing curvature. Once this is solved, I can continue my route.
One part is a polysurface made in Rhino. The other is entirely made inside Grasshopper. In the last screenshots, I baked them for you to have a better look.
Because I plan to use ShapeDiver or similar, I need to build everything inside Grasshopper and stay compatible.
Here are some parts of my canvas. Some components at the end of the line are remnants of different solutions I tried. I used the Loft component ONLY to show you, in green (earlier screenshot), where the blend should appear.
Is my canvas a mess and not the academic way to build it? Surely. Am I losing hair? Lots.
If this doesn’t help, please don’t get offended. If I’m here, it’s because I’m desperate. If I could pay a professional to do this, I would, and I plan to do so in the future. For now, I need to do it myself.
If someone kind, who hasn’t had too much coffee, could help, I would be very grateful. If not, I’ll go back to my cave.
Dear Gil,
On the forum, people are willing to help anytime. For many of us, English is not the first (or second) language. We have patience.
Now to your question. You uploaded many images now, but it is hard to work with these images.
We use them to explain what we see, what we want to know, etcetera.
To help you with a solution, you also have to upload the files youu make with Rhino. Please use this button to upload the .3dm (Rhino) file and the .gh (grasshopper) file.
That is the fastest route to good answers.
Rergards, Eef
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Thank you very much, Eef. I appreciate 
Is there a way to send the files more privately to people kind enough to help? Or a way to delete the files later on?
Regards,
Gil
@Gil has ignored advice from everyone in this thread, so clearly prefers the slow route.
@Joseph_Oster I am. What’s with you? Nothing else to do than bringing anger ? You would not behave that way if we were in the same room. Have some basic ethics. Try to also think a bit before barking, If I didn’t post my files publicly there are reasons. Please leave (you) this thread and let me with the adults.
Even if there is a case by case and each settings is different. Is there a concept / method do build a G1 surface bridge in between surfaces inside Grasshopper?
@TomTom is the only one so far with an answer and if he’s right, it seems that we can’t really build loft with tangency to other surfaces with Grasshopper native components. Did anyone succeed doing so?
My impression is that you need an overall approach to building the complete structure you want. Start with the full structure in mind, not two pieces.
Bridging a gap between two different kinds of construction is a bandage that is always going to be overly complex.
@nxakt You’re making a very good point. And if I can’t find a way to make this bridge I will need to rethink the structure and get rid of this gap.
I have two parts because there are separate options to change one and the other and to make one whole structure for all combinations will go to high number.
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Well, you cut the parts what are needed as @inno suggested.
I made a small demo on how I would do such a thing: Share only what is needed/wanted
A. In the left some original objects
B In the middle how I internalised them in gh and created an “cutting” brep around what I need
C. The result baked back again into Rhino. They can be distrubuted in a new ,3 dm or internalised into a new .gh (NB: I used a pipe, bounding box, sphere are also fast ways to create a sizeable brep)
demo-gil-EW.gh (122.3 KB)
Regards, Eef, (see also PM)
Hi Gil -
This is a public forum. If you are unable to share files in public, you should consider engaging someone as a private tutor. Posting a request in the Jobs & Portfolios category would be one way of doing so.
-wim
Not sure if it helps to value my opinion here, but
I have worked a couple of years in automotive design trying to automate this on a highly professional level. In the end most of the work ended up in a hybrid workflow. Automating as much as possible, and then working in a group of people to get perfect blends in difficult scenarios for patterns. While having developed own Bezier/Nurbs tools, I know how difficult this is on a mathematical level. And even if you properly model this in a manual workflow, you would even find it difficult to do with the right tooling. At least if you want proper geometry. Years have passed by, and nowadays there are other possibilities outside of RH/GH, but in Grasshopper this is incredible complex. So don’t waste you time on this.
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