Create a pipe from a 3D curve (spline)

[usaY3MZX]

Update: Attached the project as a file, because the link seems not to be downloadable.

The project: https://a360.co/3xZhKkQ

I have a 3D curve and want to "make it thick": create a pipe out of it, swipe a circle along it, or something like that. But unfortunately, the maximum pipe diameter, that I can create, is 0.2mm. When I increaseit, F360 says "The sweep would create an illegal surface" or "The body would intersect itself". But I don't care, I only need the final body with both intersected and non-intersected parts!

[wmhazzard]

Can you make the web link model downloadable or attach an f3d file of the model? Most likely the problem lies with the hundreds of spline points, that is way too many but we will have to see how you created the spline to tell for sure.  

[TrippyLighting]

---

@usaY3MZX wrote:. But I don't care, I only need the final body with both intersected and non-intersected parts!

---

Understood! However, the software really doesn't give a ratsa$$ whether you care or not 😉

If you play by its rules, then it'll provide with a nice non-intersecting pipe! 

[Joshua.Aigen]

Hi @usaY3MZX, I was able to create the thick self intersecting thing by sweeping a circle along a path and keep it small at first. Then I used surface tools to offset the surface then patch to close the ends, and finally stitch to make the surfaces back into a solid body. Attached is an example file.

[usaY3MZX]

Attached as a file, because downloadable links require a paid version of F360.

---

@wmhazzard wrote:

the problem lies with the hundreds of spline points

---

I doubt that 256 points is the cause of the problem, because 0.2mm diameter pipes are created correctly and even 2mm diameter pipes are created correctly, but only with a SLIGHTLY different shape of the spline. But I need EXACTLY this shape.

[usaY3MZX]

---

@Joshua.Aigen wrote:

I was able to create the thick self intersecting thing by

---

Sorry, I don't recognize my initial spline. You must have thickened some another, much simpler spline.

---

@Joshua.Aigen wrote:

Then I used surface tools to offset the surface 

---

I tried that before posting to this forum, (Surface -> Create -> Offset -> Distance = 0.1 mm), but I got "Cannot offset selected faces".

[usaY3MZX]

---

@TrippyLighting wrote:

---

---

If you play by its rules, then it'll provide with a nice non-intersecting pipe! 

---

Thank you! You were extremely helpful.

[Joshua.Aigen]

@usaY3MZX what is the purpose to creating this, maybe more depth to your question would help us give better answers. I was able to accomplish what you want with a simple spline, so it would seem that your spline just needs to be simplified in order to achieve what you want. How would I go about creating the same spline again? Once you have the solid what is the end goal? Why does the spline have no reference geometry?

[TrippyLighting]

LOL. Yeah sorry!

The best way to analyze where this fails is to actually use a sweep. @wmhazzard has already told you, the spline has a lot of control points and that often causes too tight curvature in some places.

So create a plane along path, pull to to one end and create a sketch on it with a .3mm circle.

Then create a sweep with the circle as the profile and the spline as the path.

It will respond with an error message, because the default for Distance is 1.

Set that to .01.

Then pull the sweep arrow along the path and see where the sweep starts failing.

Wit a little luck you'll be able to modify the spline area in question to eliminate the problem.

Be patient!

 This is where it fails with the setting I have mentioned above:

[usaY3MZX]

OMG, why do you need to know that? I am creating a replacement shade for my chandelier.

Here gies the model, anything else will look different from the other shades:

https://usachov.eu/misc/FockingFusion360.stl

[g-andresen]

Hi,

try this

Screencast

&

Follow the timeline.

günther

[usaY3MZX]

You mean, that I need to adjust my spline point by point EVERY time, when I adjust the equations used to create the points? The actual spline is much longer than I have shown. There definitely must be a WORKING way to thicken an existing body.

[laughingcreek]

sometimes the pipe command in t-splines is more forgiving.  won't be parametric, but that doesn't seem to be necessary here-

[TrippyLighting]

---

@usaY3MZX wrote:

You mean, that I need to adjust my spline point by point EVERY time, when I adjust the equations used to create the points? The actual spline is much longer than I have shown. There definitely must be a WORKING way to thicken an existing body.

---

As @laughingcreek has mentioned, T-Spline pipes might work.

You could also try to only create spline points at inflections only if you create this using some algorithm. This would be an attempt to reduce the number of spline points.

Fusion 360 and many other CAD systems do not allow to create self intersecting geometry. Using too many fit points will kill the curvature of a fit-point spline, leading to these self intersections. If you right-click on your spline and select Toggle curvature display (adjust scale and density)  you will see the curvature on the spline. Not exactly smooth.

The points your algorithm creates are not the same points required by a fit point spline to be smooth. In order for that to be the case, your algorithm would need to match the fit points for a smooth fit-point spline created in Fusion 360 (which has likely much fewer points). A fit point spline in Fusion 360 is a 5-degree multi-span, non-uniform rational B-Spline. Its implementation details are proprietary.

You might have better luck using a 5-degree control point spline instead. 

[usaY3MZX]

Thank you! Seems like the best workaround for now!

[usaY3MZX]

---

@laughingcreek wrote:

sometimes the pipe command in t-splines is more forgiving.  won't be parametric, but that doesn't seem to be necessary here-

---

However, this does not work on more complex curves:

Can you suggest me something?

Meanwhile, I created a sphere and duplicated it along the path, but now I am unable to combine 10 thousand spheres, because opening the combination dialog takes forever 😞

[TrippyLighting]

---

@usaY3MZX wrote: However, this does not work on more complex curves:

Can you suggest me something?

---

No, you won't get past the self intersection problem with such complex curves. That is without hand editing the result before converting the T-Spline.

---

@usaY3MZX wrote:

---

Meanwhile, I created a sphere and duplicated it along the path, but now I am unable to combine 10 thousand spheres, because opening the combination dialog takes forever 😞

---

That is simply going to take a while 😉

That and the self intersection problem makes me believe you are using the wrong type of software. A mesh modeler, for example Blender can crate and handle much more geometry and is not so picky when self intersections occur.