Line to box section tube


I am new to blender, so please go easy on me!

I would like to make a line into a tube.

IE I have a 3D line design that I imported as a DXF and would like to ‘grow/expand’ those simple DXF lines so that they are tubes (preferably square section). I do not need to keep the original lines once the tube is made.

I have searched around a bit but cannot find anything like what I’m trying to achieve.

Essentially, if you have a simple line, how do you make it expand into a tube with the centre of the expansion as the line (it could be solid or hollow, so long as the result has a surface on all sides).

Thanks in advance, I hope I am explaining it clearly enough.

Regards, Andrew

First off don’t call it a line. In Blender terms it is an edge. Edge itself has no volume. You need to extrude it to create a face, then the face need to be extruded to create a volume.


Hi Ridix, thanks for the reply.

I think I get what you mean, and indeed I have completed that to the first stage of extruding all edges at once in the Z axis, but because this is a 3D object (its faces curve in all axis) it does not create an even depth of face due to some of the edges being orientated in different space)

Also how do you then get all of the newly created faces to extrude either side of the original edges so that you are effectively ‘fattening’ the original edge geometry (if you understand)?

IE, I now have a ‘ribbon’ in the form of the original line (edge) design, how do I then make the faces wider in mulitiple axis instead of all in one direction which would not work for edges that lie for example +Y-Y instead of +X-X (if you extrude to +Y, it will not work for edges that lie ±X) (what’s worse is that any faces that lie somewhere between X and Y will be extruded in a diagonal fashion and not even)

IE again, if for example you have a rectangular shape made from 4 edges, you extrude in the Z direction to form a ribbon of that shape, how do you extrude those faces all at the same time so that they now have a thickness in both X and Y directions? And what happens if that rectangle does not lie convieniently flat on the grid? What if two of its edges are curved? How do you then get the extrusion to be an equal thickness in all dimensions, ie 0.1 blender units from any point of the original edge?

I think that is the best I can explain the problem.

Hope you can enough to help a little further!



Quickest way is to add Solidify modifier on it on your flat face geometry object. There you can specify the thickness and offset. When you get what you like just “apply” it.

Hi again,

Thanks will give it a go.

Cheers for now

That Nearly works, but I get some weird problems around the joints of the edges…


This may be due to vertex normals facing the opposite direction. Not sure though.

You don’t want to connect three or more faces on one edge. Look at this image:

Adjacent Polygon face A and B faces the same way. Adjacent face A and C face the same way as well. But face C and B is connected front to back! The face orientation is all messed up. If you add solidify modifier, software don’t know which direction you want to add thickness between A and C or C and B.

In your case remove this T corner. Add face manually after thickness is applied.

Hi Again,

I will give that a go. and let you know.

I also wondered about the trick to assign a shape and path (not sure what this is called, but you basically separately make the cross section of the ‘tube’ you want, then that gets transposed onto the path (in this case the edges). Would that be a possibility with this?

Regards, Andrew


It’s getting better, I looked at the normals and found a few faces that were incorrectly oriented and now have this…

I tried the deleting face thing, but this made some strange problems that my re constructive skills don’t allow for just yet, but think it might be the way to go.

In area “A”, remove the mesh that is coming off the main shape as a T intersection. You will get a gap when you add thickness with modifier. No problem. Just apply the modifier to convert thickness into mesh. And just manually bridge the gap.

As for kinked corner “B”, in Solidify modifier activate “Even Thickness.”

Hi, and thanks for your detailed reply.

Well, again I have learned a new trick thanks to you and can now manipulate the deleted vertices. However, due to my original concern (re the first extrusion in Z direction distorting the 3D shape), the problem is that the horizontal (I shall call them beams) were originally connected to the outside face of the geometry, which means that when you delete the connecting mesh and reconnect to the new inner face, they dont line up in the Z direction and now have a step up to the connection.

In other words the problem stems from the first stage of extrusion from the original edges.

Is there some way to extrude the first stage according to the curves orientation in space. I think what I mean is that is there a way to align the normals to a tangent of the edges orientation so that the extrusion maintains its thickness in all areas?

I dont think I can explain this properly, but I hope you get what I mean?



what about useing curves? if he uses a bezier curve and sets it to take its scale from a bezier circle he would then have an edge, with a ‘tube’ around it…with open ends…if im correct his is essentially what your trying to achieve?

could he convert his edges to curves?

Hi Evil Moon MOose. That was the sort of thing I was wondering about. Not sure how to do that allthough I have seen some examples.

Trick would be converting it to a bezier curve. I know I can convert it to mesh, maybe it will then reverse to a bezier?

OK, have the shape in Bezier form, what next?

OK, I found a tutorial on curve modifier, but it wont work for this geometry because it is not a continuous curve. It starts to do the outline and as soon as it gets to the first T connection, it cannot continue.

So, I guess I could use this method, but would have to disconnect all connecting edges (now curves) and modify each accordingly. A bit laborious, but should work.

Is there any way to make the target tube in this technique to automatically scale to the right length? Or do you have to trial and error it until you get it right?

Best regards and thanks for your input all.



Just wanted to say thanks for all your help.

In the end I found a very effective way of doing it which was to convert the original edges to bezier splines, then simply modify the splines to give volume and bevel. Very very simple in the end!

Thanks again, Andrew