@tig said:

You need a 3pt-circle tool rather than a 3pt-arc tool to be sure of the result...

I found out that in this case it is simply better to have the arcs first!

Than I need to project rail 1 or 2 onto the plane on y, connect the arc's end points with each other and than I have to draw a line from the arc's highest point to the center of this line. Than I need to use EEbyRails to extrude each of the herewith created part of the projected path along those rails. Very nice results!!

I hope you get it from the image. My English is sick today... It is really great and must become part of some (maybe even existing?) script. You can't do all the steps involved over and over again. (Is there some documentation for EEbyRails and Curviloft with examples so that it is easier to access them from own scripts???)

Have a nice weekend.

@tig said:

To ensure things ARE 'coplanar' draw a large grouped rectangle 'plane and locate it...

That's what I do and did. Rail 2's Noncoplanarity (? ) was an accident happened while playing around. But even if Rail 2 in my model is coplanar you can't draw an arc with SU's Arc Tool that snaps to Rail 2.

@tig said:

Unfortunately unless the line-end as the 3rd point picked is a special case [e.g. central] it won't be on a node of the arc [or the circumference]...

I tried to use Didier Bur's 3-Point-Arc script but I don't understand it. (Guess he's talking about different point or so.)

@tig said:

I hope this illustration explains how you might achieve a '3pt arc' [or at least a pair of concentric same-radius arcs] that passes through AND 'touches' all three of the points... [there are a few 3pt circle scripts available to download - they can be very useful...][attachment=0:3pjkgyon]<!-- ia0 -->3ptArcs.PNG<!-- ia0 -->[/attachment:3pjkgyon]

Thanks for your help, Tig. I am going to try those.

@tig said:

It would be better split in half vertically and then mirror/joined afterwards.
The mid 'spine' is not coplanar either.
Also split in several sections horizontally...
The uneven segment count in the subdivided curves does give some mesh smoothness issues.
BUT all in all it's nearly there ?[attachment=0:2uloo1b2]<!-- ia0 -->Capture.PNG<!-- ia0 -->[/attachment:2uloo1b2]

Thanks for the suggestions, Tig.

This model is not really supposed to be anything. I am just playing around with curves to see how things can be done in general.

And this thread is about the arcs. Even if rail 2 - the mid spine - is not coplanar I would like to know how to draw an arc or curve that goes through it.

@jean lemire said:

If I did not guessed your problem, please post your model...

If the top line is not perfectly centered between the two lower line, the inference engine will try its best to snap to the height of this line.

No, that is exactly my problem. But sometimes C simply is not directly above the center of the distance from A to B. Still you want or need an arc going exactly through C.

In my model everything that is not grouped was drawn with SU's Arc Tool, but three of those arcs had to be changed manually, because I wasn't able to make them go through rail 2 using just the Arc Tool.

arc.skp

Is there an arc tool that really always snaps when it says so??

Komisch auf Englisch, aber okay...

I think it is, because you just have the circle and the rectangle. And not three shapes.

I used to skate a little myself two decades ago and we don't have skateparks like yours here: So I don't mind if you just show everything you are allowed to show.

Because I am really missing the feature I just cannot resist to ask here, too.

If you are planning new features for Curviloft it would be great when selecting of curves that are part of different components could become possible. (I mean like the right one where two curves can be one contour.)

Of course I know, that exploding is possible but it is really unconvenient. Especially, because right now you cannot have one instance of the component connected to the path you want to loft with while having the parent somewhere else where it is easier to edit. (You can but if you make the child unique for lofting the connection is gone...)

@tig said:

Do NOT Explode the Curves - you need those later !

Thank you, Tig. If you are ever bored, being able to select those (components) without exploding would be a really nice feature.

My plan was to use mirrored components, especially because I wanted curves and corners in my profiles.

Unfortunately neither Tig's Extrusion Tools nor Fredo's Curviloft treat/accept those four curves as one being inside "their" components.

What can I do here??