# Follow me with portion of circle

Hi there, the follow me tool drives me crazy… I made a first vid to show my problem, this vid has made me understand why the problem occur,
Then I made a second vid that show a “solution”, but this solution involve a new problem.
Let’s start with the first vid. It show a problem when trying to achieve the follow me a portion of circle. You never get a real half circle a the end. The end of the vid show the problem with an hexagonal shape. Then we understand that the follow me in fact create the shape with a right angle from each segment of the path.
https://www.youtube.com/watch?v=bQbjy9BrmXA

The the second vid show a solution. Let’s rotate the circle to the middle of one of its segements and now we have a real half circle. But now, the diameter is false… The error could be reduce to a very small value but there’s still an error that, one day or another will leads to encounter problem in our geometry.
https://www.youtube.com/watch?v=xfojtoIgz2g

How do skilled people around here are dealing with this issue ?

Thanks in advance

@ene_su created a bug report a few months ago, SKOR-15235 in our system. I think it covers the same concerns. I don’t know how it is progressing.

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See this SU file for ideas.

Half torus.skp (195.2 KB)

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Thanks,
I often cut the whole shape to the wanted portion but with some complex shape it so often leads to missing segments and shape than cannot be converted to solid.
Maybe my missing segments are related to the size of the shape, I often have very small segment.
I think i’ll try to recrate my project by using meter instead of mm, just making as 1 meter = 1 mm… Let’s see if it’s any better.

Thanks

What I feel strange is that SU treat perfectly every segment ecxept the start segment and the end segment… Definitly a bug that could be solved IMO.

You can fix that by rotating the arc or circle so the start point is in the middle of a segment.

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If the face to be followed along the path is not perpendicular to the first segment of the path, the Follow Me tool rotates it so it is perpendicular before doing the follow me operation. I also stops so the last face is perpendicular to the last segment of the path. The trick around this is to add segments that are perpendicular to the face at the beginning and the end of the path. Some trimming may be needed when done.

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Actually it projects the face to perpendicular instead of rotating it. Starting out as a circle not perpendicular to the first segment of the path…

Projected to become an ellipse during Follw Me.

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Yes Dave, I used the wrong verb. Effectively it projects the face so there is a deformation. For example, a circle may become an ellipse.

Sorry for the mistake. English is my second language after French

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No worries, sir.

That’s what I made in the second vid. But by doing this, the diameter of my shape is wrong on the red axis (or green or blue axis…) For sure it leads to geometry problem at a moment.

But yes in fact it’s possible to get the good diameter by scaling the circle… Maybe my solution.

What is it you are actually trying to model?

It doesn’t really matter, I’m talking about geometry in SU. The solution of turnig the circle to have the start point to the midle of a segment work but you must be sure to never use the initial diameter value anymore in you model as it is lost.

Scaling the circle to get the diameter to it’s original value don’t work. The scale value isn’t a decimal number and you never fall on the intial diameter.

It should be better to use the full circle for the follow me and then cut the shape to the desired portion. But for some reason (maybe the small size of my segment) it often don’t work properly.

It’s maybe a mistake but I like to use circles with 144 segments. It gives me 2,5° of accuracy… As I said above, I should maybe work in meter instead of millimeters usin 1m = 1mm. Scaling everything at the very end (exporting).

Sorry. I have some methods to work with getting desired dimensions but I guess this thread isn’t about that. I’ll move along. Sounds like you have a way to deal with it anyway.

Please tell us more

Scale can be exact, just add the units.

Yes, small geometry is a long understood problem, which will be exacerbated by using a large number of segments.

Use the Polygon tool instead of the circle and tap ctrl to change the radius from inscribed to circumscribed, then weld it before follow me so you don’t have hard corners. For this usage a circle is just a polygon with soft corners.

We have long been asking for this ctrl option to be available on circles for this very reason.

It can be a square root ? I guess there’s a square root somewhere to go back to the initial diameter.

Anyway thanks fot thoes infos, I’ll try what you suggest

Add the unit when scaling.

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Wonderfull explanation, thanks.