Spline tangent erased when keyframed

That make sense, an object can have multiple tags, but it seems you can use neg numbers which I don't understand.
Hiroto once again saves the day/week/month. (y)(y)

I made a new layout to help fine tune F-curves.

Spline Editing Layout.jpg
 
Thanks to Frank Helmut and Hiroto.
I'm most grateful for your help.

View attachment 35819
Hi, Zoo. I'm missing something here, how to make the cars point to the rail. I made a moebius object, and did two ring cuts - one for the path, one for the rail. Using Hiroto's polygon2Spline script, made those cuts into splines. The car tracks, tangent to the path spline, but I can't get it to bank to the rail spline. There must be some magic words I'm missing.
 
:unsure: If I understand you correctly, you are modelling an object traversing a Möbius strip.
:devilish: The rail on a Möbius loop will be a bit tricky as the basic spline is transversed twice (position 0 to 1 and then on to 2). As a result, you need a reentrant spline "on either side".
:sick: I just started experimenting there and have not quite worked out a solution. Intuitively I think that a torus knot is required for the rail to control the orientation. Alternatively, Master Hiroto´s Java script on guided helices may be a solution. I found a couple of scripts for torus knots in my toolbox, so let's see what happens...
 
It sounds like you have the car tracking fine but it's not banking to the second "rail" spline.
Can you upload a simplified version so we can check it out.
 
:poop: Yep, looks like I did not read the question correctly.
* If this does relate to Möbius strips:
* In this case: the rail needed for a Möbius strip is just the edges of the original strip when rotated by 90°. However, this assumes that the Möbius strip is a path tweaked by 90°.
* As has been mentioned in the old thread Frank B has been referring to, the mesh geometry at position 0 (start / end) needs tidying up as a rotated sweep on a closed spline results in a bit of a mess.
* ZooHead´s suggestion for an upload of a simplified version would be constructive.

Screenshot 2022-04-11 at 13.35.26.png
 
It sounds like you have the car tracking fine but it's not banking to the second "rail" spline.
Can you upload a simplified version so we can check it out.
Thanks. Here's a quick and simple version. I made the moebius by sweeping a rectangle around a circle, with a 90 degree twist. Deleted the end polygons and bridged. It was surprising to me how well ring cut and loop select worked, as if the end patch was not there. Splines were made with the ring cuts using the Polygon2Spline script.

It is not a critical project, just for fun and learning. Our Department of Transportation seem to have made a quantity purchase of roundabouts, and is installing them at random intersections all over. They might have hired Escher to do their highway interchange designs. I thought it would be fun to depict a roundabout as a moebius, in order to be able to quadruple the traffic capacity or reduce the surface wear.

edit: changed the orientation of the car so it drives frontwards, not sideways like me on ice. Added an upscaled path spline as a rail, per Frank's suggestion.
 

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  • MoebiusTest.zip
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Ok - to avoid the flipping while running around the loop you need to use a rail spline - which just can be an upscaled duplicate of the Path.
Please have a look into the attachment.
 

Attachments

  • AroundTheMoebiusLoop.jas.zip
    42.1 KB · Views: 107
:poop: Yep, looks like I did not read the question correctly.
* If this does relate to Möbius strips:
* In this case: the rail needed for a Möbius strip is just the edges of the original strip when rotated by 90°. However, this assumes that the Möbius strip is a path tweaked by 90°.
* As has been mentioned in the old thread Frank B has been referring to, the mesh geometry at position 0 (start / end) needs tidying up as a rotated sweep on a closed spline results in a bit of a mess.
* ZooHead´s suggestion for an upload of a simplified version would be constructive.

View attachment 38398
Yes, thanks! That is what I did. The bridge tool seems to clean up the end geometry pretty well.
 
One tip with the Polygon to spline script, if you're using Bezier Splines you need to use the Soft
Interpolation command after you make them editable or all the points along a curve will be bent.
 
It's working but the Rail Spline is not in the right place in all places.
Try scaling up the mobius object or use normal move to make
the Rail Spline so it's always 90 degrees to the "roadway".
 
Like this should work.
Thanks. I tried making a second moebius, sweeping a larger square, doing a ring cut in the center and making the rail from that, but the car still seems to flip. There must be a step that I am missing.
 
I'm getting the same thing and I think it may be because the
start end point of the splines are not at the same place. :unsure:
 
I used bridge tool after deleting the confronting polygons at start/end - optimize seems to help also. Just then select edge loop to convert into splines.
 
It works until the car gets to the bottom, then Cheetah gets confused.
 

Attachments

  • Moebius zoo jas.zip
    92.7 KB · Views: 103
I think I got it now. Thanks for all of the help, Frank, Helmut and Zoo.
Here is what I did:
1) optimized moebius.
2) duplicated optimized moebius, and used polygon2spline to create the path spline. Soft interpolation.
3) duplicated optimized moebius, selected all polygons, and did a normal move. Created rail spline from that.

It seems to be working now, although maybe still some of the confusion that you are getting, Zoo. I really appreciate all of the help!! Thanks so much!!
 

Attachments

  • MoebiusRoundabout.zip
    77.9 KB · Views: 102
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