Full Version: Extend / extrude "tangentially"

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Hi,

I would like to extend the tube "tangentially" but the
extrude command creates a buckle.
How can I achieve an "organic" extension without seams ?
Thanks TOM

Image Attachments:
file.jpg 

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Hi Tom, currently the Extend command only works on curves, not surfaces. I want to change that in the future but typically the best way to make an extension like that is to extend the original curve used to construct the surface in the first place instead of trying to extend the surface after it has already been constructed.

If you can post the .3dm file I might be able to try out some things and give you some other suggestions though.

- Michael

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Hi Tom, also one other tip - one of the first things I would do if I was able to load the actual geometry you show there would be to do an "untrim" on the surface and see how far the underlying surface already extends.

You do an "untrim" by selecting all the edges of a surface (not joined to others, use Edit > Separate to break it out) and then do Delete.

- Michael

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Looks like the file was not uploaded. Ill do it now.

So it is possible to "extend a curve" ?, could that I have overseen
this command till now.

Attachments:
file.3dm

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Hi Tom, yes the Edit > Extend command can be used to extend a curve.

For your case here you can get an extension by untrimming the surface to recover the full underlying surface and then extrude that edge. I've attached an example.

It's generally better to have done the extension on the original construction curves so the surfaces have that extension in them when you make them.

- Michael

Attachments:
extended.3dm

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Why don't make an Extrude with Direction with helper Lines ?

I just make an Shell for see something :)

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The ending edge of the current surface is not a circle because the surface is cut at an angle. Note that turning on control points you can see the underlying surface is like this:


Untrim the surface and then you can get a planar end circle edge that can be extruded.

- Michael

Image Attachments:
trimmed_end.jpg 

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Of course it is a possibility, but how to get the right XYZ angle ?

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Tangent Helper as above ?

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>>Hi Tom, yes the Edit > Extend command can be used to extend a curve.<<

Great ! downloading the file and having a look !

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Tangent Helper as above ?

Yes thats cool. Will have a look at both of your kind tips !

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An extrude by a single tangent direction won't be quite right because the tangents are slightly different on each side. That's because the surface is cut at an angle as described above. They're only a little bit different though since the surface is only very slightly bent so it will be hard to tell visually.

But if you want a precise result then doing the untrim will recover a planar ending edge that can be extruded to get an accurate tangent extension.

- Michael

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Michael, I am using the extend command all the time if I have another curve to extend it.

I thought that you meant that is also possible extend a curve into "empty space",
but this does not work, doesnt it ?

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Hi Pilou, here's an example with a tube that is more tightly bent and cut at a greater angle to show you how there isn't one single tangent direction in a case like this:







When you untrim it then you'll get a natural tube end which does have a single tangent direction.

- Michael

Image Attachments:
pilou_tangent1.jpg  pilou_tangent2.jpg  pilou_tangent3.jpg 

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Hi Tom,

re:
> I thought that you meant that is also possible extend a curve into "empty space",
> but this does not work, doesnt it ?

Empty space does not have to stay empty, you can draw in a temporary boundary object, extend to that and then delete the boundary object.

- Michael

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Hi Tom, also re: Extend command - the boundary object does not have to be a curve it can also be something a sphere or a plane.

- Michael

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When you say "Untrim" in this case of this tube what is untrimed ? Curve? Section ? Surface ? ...
Untrim is "Separate" ?

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Hi Pilou, it's this surface here that would be untrimmed, the same one that wants to get extended:



To untrim it, use Edit > Separate on it first to make it an independent single surface not joined to anything else. Then select all its edges and do a Delete. The trimming boundary will be removed and the full underlying surface will be recovered.

The other end that will not be extended needs to be retrimmed.

- Michael

Image Attachments:
pilou_untrim.jpg 

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OK!
And this
Extrude --> Boundary Sphere ?

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Hi Pilou,

re:
> Boundary Extrude --> Sphere ?

I'm sorry I don't understand this question. The mention of a sphere above was about the Edit > Extend command, not the Extrude command.

- Michael

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