Creating opening in "knotted" pipe

[lob23]

Hi all,

I am trying to create a sort of a knot and have a hole go through. I managed to create the geometry using pipe, but since I want this “fat” node, it creates a closed polysurface with intersecting surfaces which does not let me do any operations. I have tried to shrinkwrap it but also with the mesh it doesn’t seem to work. I have also created a NURB from the mesh but to no avail. Neither with Makehole nor with intersection nor with slice it works.

Any help would be much appreciated.

Thank you

[martinsiegrist]

Divide it into sections that do not have self intersections.

[keithscadservices]

This might help:

First, turn on history. I’ve right-clicked and checked “always record history”. It doesn’t seem to be obeying not for me at least… but anyways, click this button each step (don’t worry it’s only a few):

Instead of a pipe I’m going to do a sweep1:

Now this part might suck, but it involves manual point editing. You can select the curve, use “PointsOn”, then set your selection filter to Control Points only, and manipulate the curve:

I found it easier to do this in “Ghosted” display mode.

The history also allows you do scale the original circle used for the sweep:

If you sweep with multiple shapes you could also use OrientOnCurve and place circles within the knot… then tighten those up to squish the string section within the actual knot to make it “tighter”.

[lob23]

Hi! Thanks for the answer. How would you do that? Noneof the boolean operations work

[lob23]

Thank you for the answer. This is exactly how I modelled it, but that is not the issue…

[martinsiegrist]

How to shell a self-intersecting shape

You will have to split the pipe and rebuild some of it. Below is a part of it. The crossing can be solved by splitting the surface with intersection curves. The loop is more complicated. I deleted the part which had the self intersection and rebuilt it with a network surface and 4 blended “rails”. The part shown below is a closed polysurface. [image] selfintersectingsrf.3dm (2.6 MB)

This was a simpliefied example for a similar problem.

You might have to duplicate the object and use surface trimming to split the knot into separate pieces. Cap these and union the first with the second and so on. If you’re still having problems, please post your Rhino file.

Here’s some of more knot stuff:

Shoe laces

Various knots I created based on 3D scans with my Artec Leo. The scans were used as a guide for remeshing. The meshes were simulated with Kangaroo. The shoelace knot was the culmination so far because there are both self intersections to avoid aswell as collisions in between the two loops. [20_10_29_knot_02] [20_10_29_knot_01] [20_10_21_knot_04] [20_10_19_mastwurf] [20_09_01_vertical_dodekaederstumpf_seil_mit_vier_knoten] [20_05_01_knot_03] [20_04_30_knot]

Simulating Rope Knot tightening using Kangaroo 2

[image] [image] FigureOfEight.1.gh (52.6 KB) You could use the rod goal instead of the line goal. The trick is to start the solver with a high length factor and while it is running, you drag the slider down to let’s say 0.3. In some cases the grab tool can be useful to pull one rope over the other. I’ve done a few knots some years ago. My main goal however were knots with flat webbing so I had to use slightly more complicated goals. You’ll find some images and animations here: Shoe laces …