Unwanted twist in connected spline

[tom-238576]

Hi, this is actually based on one of Dr Sassi's projects that I found which solved my problem of creating a mathematical trefoil knot, so thank you for that!

I've got a secondary issue that i've spent a year (on-and-off) trying to solve to no avail.

At the point where the spline begins and ends there's a 359° twist to get back to the beginning again, which causes issues as soon as the profile isn't perfectly smooth, or when using any materials which reveal the inside core (transparency etc).

How can I fix this please?

I've also got a separate project where this is made from a dedicated hand-drawn spline (not good, and still exhibits the problem) as well as a separate project built from a pure formula, but the formula spline has unexpected behaviours, and 'breaking' it to make a 'plain' spline re-introduces the twist at the start/end point.

Only Cinema's own primitives don't show this twist behaviour, and every custom spline i make appears to twist at the start/end point.

please help if you can, and thank you in advance,

Tom

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[Dr. Sassi]

Hi Tom,

Please have a look here; perhaps you can reuse the knot spline. Both are pretty much the same
CV4_2023_drs_23_MOkt_03.c4d
CV4_2023_drs_23_MOkt_11.c4d

All the best

[tom-238576]

Thank you — it's fine when using a sweep, but I need it to animate traveling along its length continuously which a sweep can't do due to there only being controls for start and end, not offset. When using these splines with a cloner, or a spline wrap or an align to spline tag (or any of the other uses for a spline, the beginning vertex has a complete twist in the rotation, which makes it almost unusable. I've attached a project file with the knot above showing the issue:

twist in looping spline.c4d

[Dr. Sassi]

Hi Tom,

You didn't mention this.

Please have a look here, traveling along the Spline. Adjust the Plane's segment count to your needs.

CV4_2023_drs_23_MOkt_21.c4d

All the best