carbon frame (giant)

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 From:  Jack Russel (JACK_RUSSEL)
1012.1 
hi,

need some help, please ...i try to get the organic form of this carbon frame ... but i don't know how to get the tubes together ...

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 From:  Michael Gibson
1012.2 In reply to 1012.1 
Hi Jack, one idea is to build a sweep that sort of arcs through that whole area, like the attached bike_sweep.zip, then hack off the part of the sweep you don't want to keep, either by doing a boolean with the other part, and then filleting the in-between, or possibly trimming with a profile curve and then doing a blend between some open area between the 2.

That might give you an idea, I'll see if I can come up with some more for you later but it won't be until tomorrow.

But generally branching structures can be really hard to build directly, it is usually better to sort of build more simple broader things that extend beyond and then trim those back.

- Michael
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 From:  Jack Russel (JACK_RUSSEL)
1012.3 In reply to 1012.2 
thx, michael ... but i don't get it anyway ... can you or somebody else give me an advise, please?
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 From:  Frenchy Pilou (PILOU)
1012.4 
Maybe something like this but the added curve must be constructed with a good path :)
And make the same upside
just speed answer not very well construct the curve ;)

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Pilou
Is beautiful that please without concept!
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 From:  Michael Gibson
1012.5 In reply to 1012.4 
Hi Pilou, that will definitely fill in that area, but those pieces will end up with sharp creases where they touch each other instead of being smooth.

Jack, I'll show you some more step-by-step details of that earlier method that I posted just a bit later tonight.

- Michael
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 From:  Michael Gibson
1012.6 In reply to 1012.1 
Hi Jack, it can be pretty tough to create smooth branching structures that have many junctures in them.

Here is one method that could work for your case here.

I started with your curve framework, mirroring a couple of pieces:



Next from the side view I drew the curve shown in yellow here:



That is now used as one of the rails for a 2 rail sweep:



That sweep now creates one major element of your shape. Next I mirrored and stretched out some of the curves on the right side, and then used Loft with the closed option to create this second shape on the right side:



That's the other major element. These pieces are running into each other, but that's ok, the next steps are about fixing that up. Next I went to the side view and drew this curve shown in yellow here, it will be used to cut the sweep:



Then the sweep is trimmed using that curve as the cutting object:



Another view of the trimmed sweep:



So that trimmed sweep is an interesting part. It would be quite difficult to try and create the above shape just using outline curves only (I mean like trying to sweep or loft that final shape directly instead of using trim). Sometimes it is easier to make pieces extend in larger swoops and then trim out the areas that you don't want.

Next I switched to the front view and drew an outline curve that generally followed the shape of the hole in the sweep:



I actually drew only half of that curve and then mirrored it to get symmetry, but then I also joined the 2 halves together, turned on control points and deleted the control point where each half touched, to fuse them together into a single segment. That just ensured that the curve would be smooth and would also end up being a single edge when it was used as a cutter for Trim.

Then I trimmed the right-side piece using that curve as the cutter:



Next I selected these 2 inside edges where the holes are at:



And then using Construct / Blend will fill in that area with a smooth surface:



The final result:



This one was done kind of quickly, you can tweak the shape quite a bit by making the width of the right-side piece match the width of the left sweep part a bit better, in this version the right-side tube is kind of bigger.

So the basic idea here is to try and build that thing in pieces, but actually not too many pieces. If you break things into a whole bunch of little pieces you will be able to surface all of them, but it will be difficult to maintain smoothness between each little piece. If you create fewer broader pieces, it can be easier to get a smooth result, like that sweep is able to generate a nice smooth curve for the whole left side of the shape.

Then combine the pieces together either using fillets or blends. In this case I tried filleting, but it was a bit bunched together since the lower tube is a bit narrow and kind of curves fairly tightly, it was easier to make a more gentle shape there by trimming it to my own drawn outline curve rather than the constant distance type trim that filleting generates.

I hope this helps, let me know if you have any questions on any of these stages or if you get stuck somewhere.

Model attached as bike_frame_branch.zip .

- Michael

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 From:  Frenchy Pilou (PILOU)
1012.7 
cool trick with the curves given :)
Maybe in the reality intersection curves will be more straight and the tube more cylindric?
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Pilou
Is beautiful that please without concept!
My Gallery
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 From:  Michael Gibson
1012.8 In reply to 1012.7 
> Maybe in the reality intersection curves will be more straight and the tube more cylindric?

Hi Pilou, yes I think so. Making that tube to be less bowed in should also straighten out that intersection area.

- Michael
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 From:  Kurt (KURTF)
1012.9 
Excellent thread. I've said it before, MoI is not only easy to use, but Michael's explanations of HOW to use the tool are just amazing.

Just the teaching and examples are worth the price of admission.
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 From:  Jack Russel (JACK_RUSSEL)
1012.10 
hi michael,

thx a lot for your full description ...
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