Thank you for your explanation but for example for making a curved ramp that gets up and back down, what I do is to place vertical lines down at the ends of the profile curve and another vertical line where i want the upper part of the ramp. Then taking the upper edge of the resulting surface, I make a second sweep for giving that profile a width. Thats how I tried to make the ramp i showed above. The question is, how can the scaling rail be used in that situation?

Hi ed - it's hard for me to really figure out what you're describing with the ramp, do you have the 3DM model file that contains the various vertical lines and profile curves that you're describing? If so then please post it, it will be a lot easier for me to understand it by looking at a model file.

- Michael

Hi ed, thanks for posting the sweep file, I got it from your post in the other thread (here http://moi3d.com/forum/index.php?webtag=MOI&msg=4737.148).

So the part that's a bit unusual about your case here is that you've got 2 curves that are totally to one side of the sweep rail here:



Then the middle one is hanging completely off the other side of the rail:



The way 1-rail sweep works is that the profiles basically morph from one profile into the other profile as they step along the rail - by making the profiles basically go through an extended morph because they're on totally opposite sides of the rail from each other that will sort of introduce more movement in the profiles and make things harder to control.

To get more control over the shape in this particular case you probably won't actually use a scaling rail, but instead use a 2 rail sweep so that the profiles can be more simply positioned all inside the 2 rails - that would be some kind of curve structure more like this:





With the rails positioned like that you are then more directly controlling the outside edges of the generated surface by the shape of that rail curve, rather than having the outside edges being generated second-hand by the result of transitioning profile curves.

In fact you can probably focus more on just having 1 profile and the 2 rails like this:



Does that give you the kind of control that you are looking for in the generated shape?

3DM file also attached.

I got these particular rail curves by rotating your other one a couple of times, using Orient line to line and Revolve axis a couple of times.

- Michael

Thank you for your answer Michael but I'm looking for something a little bit different.

I have those two curves below the rail cause what I'm trying to find is a curve that i can use as a rail for a ramp that starts on the floor and then gets up and finally it gets down to the floor again. For that I made those three profiles for finding what in your example is the second rail, cause that second rail is not so easy to draw. So I tried this method looking for the upper edge of the surface that resulted from the tree profiles and one rail sweep. That edge is what I'm looking for but the sweep makes that S transition i mentioned earlier and i know you have it in your todo list.

I can't just draw an upper rail from the beginning because I want a soft curve that starts on the floor, gets up and then gets down again. Whats hard of this is that I draw the first curve on the top view, but sometimes that curve has a lot of points and lifting the middle part of that curve point by point gives me an irregular curve.

Hi ed, sorry I'm not sure that I'm really fully understanding what you're describing again.

> I can't just draw an upper rail from the beginning because I
> want a soft curve that starts on the floor, gets up and then
> gets down again.

If you know the kind of shape you want, then why is it that you can't draw a curve that has that shape?

You may need to do some various kinds of editing on the curve, like placing in a bunch of points for the path and the moving control points up and down in elevation to give it the up and down form that you want.

Then when you have the curve that has the softness and up and down shape that you want, you can then build a surface from it using the technique I showed there, where that curve will become one edge of the generated surface.

You can create curves that are not planar in MoI - it's easiest to initially start out with a planar curve but you can edit individual points in elevation to create a curve that goes up and down like it sounds like you want.

- Michael

Hi ed, also there are some other tools you can use to help you construct a curve that has the shape you want. The new Transform > Deform > Flow command in v3 may be particularly useful.

That Flow command allows you to remap a curve that follows a straight line to deform it onto a curved path.

For something like I think you're describing, you can use it to make an initial 2D curve that has the rise and fall that you want that has a base line underneath it like this:



So that basically focuses just on making the elevation rise and fall part alone.

Then you can create an additional path curve in the Top view something like this:




Now you can select your inital "rise and fall" curve, and run Transform > Deform > Flow, pick the line underneath it as the base curve, and the curved path that was drawn in the top view as the target and it will generate a curve like this:




Doing it that way will allow you to kind of focus on the rise and fall and the path as separate components and that may be a lot easier than doing stuff like individual control point manipulation directly on the 3D curve.

But it will all come down to you creating a curve that has the shape you want - if you want to control the shape of the edge of the surface to have some particular qualities, you can make that happen by making a curve that has that kind of shape and using that curve to generate the surface as I showed before.

- Michael

I made this to try and help:



But I really love the flow method presented!

Thats clever burr! but I think the flow method is great! Thats what I'm looking for, thank you Michael for your patience.