Michael.

Would it be possible to allow the Rail Revolve tool to scale the profile curve along the axis as it follows an undulating rail curve i.e. get the surface edge to follow the blue curve in the attached pic?


Martin.

Hi Martin, I don't believe that's possible with the current mechanism that Rail Revolve uses, which is an exact construction technique, meaning it applies weights in such a way that the revolved surface exactly passes through both the profile and the rail curve.

Something like what you are describing there would have to be done with a much different approach, more like an iterative shaping type mechanism that generates a bunch of cross sections and essentially lofts a surface through those sections. Sweep works like that.

But I'm also not sure exactly what kind of result that you're looking for either.... What kind of behavior would you expect to see in the shape where the path is going up or down? What if that path goes up so far that it actually goes higher than the top of the profile?


For now anyway you would probably need to put in several more profiles and then use Network to build something like that rather than rail revolve.

- Michael

Hi Michael.


I was looking for a way to cap the ends of irregular shaped tubes etc with a specific profile shape that follows the contour, sort of like a cross between what an Nsided patch and the normal Rail Revolve achieve, but I see now that it's quite involved.

Maybe the attached file shows what I was looking for, except the green and blue surface edges track their respective rail curves in the Z axis, whilst the surface also reflects that change in Z axis scale also.

Thanks for looking.


Martin.

I don't get the second example at all.

But I think the first example simply needs a different approach: http://goo.gl/xazeXn

Hi Martin, for your example file you might want to use Loft for that kind of thing, place a top point in the same plane as the last loft profile and use Loft Style = Loose to get a revolve-like rounded tip:






I looked into it a little bit more and it looks like it might be possible to get an exact rail revolve to work with a path like this, it looks like it's possibly a limitation of the geometry library but one that may be fixable. I'll investigate it some more.

- Michael

Hi and thanks for the replies, ttype (STRUBE) and Michael.

Michael.

I'll give Loft a good try on the job I'm doing. With a bit of fiddling, it might well do what I need.
I must say that I never thought to try Loft as I didn't realise it would work with 3D curves - but I know now:)

Thank you very much for taking time out to see if this is possible to do and I hope luck's on our side.


Martin.

Michael.

I came across this link whilst searching for ways of modelling a guitar body and it reminded me of this thread I started. http://docs.mcneel.com/rhino/5/help/en-us/commands/railrevolve.htm

I know you've been wrapped up with the Hidden Line Removal stuff of late (looking very nice), but when I saw this Scale Height option already existed elsewhere I was keen to see if you thought it was worth pursuing.



Martin.

Hi Martin, it's still on my "todo" list for this beta to look into making rail revolve work on non-planar rails like your example in the start of this thread.

Will that handle what you need here or does "Scale Height" do something different than that?

- Michael

Hi, Michael.

Yes, I'm sure that scaling the curve along its axis will do what I was asking about.

I linked to the Scale Height option at the Rhino website purely for interests sake because their little video shows that they've also included the option to keep the height of the Profile Curve fixed whilst it tracks along a non-planar Rail Curve and that was something I hadn't thought about.

Thanks again for looking into this.


Martin.

Michael.

Thank you very much for getting this into MoI v3!

I've been playing with the new feature and I know I'm going to use it all the time - I think it's huge development of the tool. I hope other users of MoI make use of it too.

Just one limitation that I've found is that if the axis of revolution doesn't coincide with the inner end of the Profile Curve, then the surface no longer follows the 3d Rail Curve in the up/down direction. Video here in case my explanation isn't clear http://screencast.com/t/KFNGxmCaFaQ.

I mention it because I've recently been using Rail Revolve with very large radii to create surfaces that are just different enough from Rail Sweeps and Lofts to be quite useful to me, and if it were possible to have the new 3d component present here too, then that would be super. The work-around that I've found is to extend the Profile Curve to the axis with a straight line and delete it and its associated surface later. Another video for this method to help explain what I mean http://screencast.com/t/GJWmaCBw.

Great work, Michael.

 

Martin.

Hi Martin, yeah the non-planar rail revolve support is in here, I hope it will be useful!

And yes - in order for it to kick in, the profile curve must touch the axis of revolution at one endpoint. That kind of helps to make the origin of the scale to be really clear - the vertical scaling happens from that axis point. This makes it not dependent on the particular pick order for when you draw the axis line.

If you want to get it for something that does not touch the axis, then just like you saw you will want to put in an extension line with the extension line touching the axis and then you can remove that later.

- Michael

OH MY GOSH!!!!

This was something I wanted! =-)

Finally! This feels so intuitive for Rail Revolve.

So here is a quick example:

Woah! good call Martin, great implementation Michael and great execution Mike!

Who said organic stuff is not for NURBS ;)

-

When you say "great implementation" that is something who is yet inside the actual Revolve by Rail ?

What I mean Pilou is, Martin requested the feature and Michael made it happen nicely.
French translation: La mise en œuvre

Is that what you're asking?

-

Ah OK I was beliveved that was a new script or function in this thread! :)

Michael.

I've been getting some great results, but I'm attaching one that's failed for some reason that I can't see, so I'm assuming it's a small bug.




Martin.

Hi Martin, thanks for posting the file. Yup, that's a bug - the bug is that it looks at segments and if a segment is on a parallel plane with respect to the revolve axis it thinks it does not need the additional processing. The bug is that it should be checking this planarity across the whole path curve and not just on individual segments.

It should not be difficult to fix for the next beta release. In the meantime, since the problem only happens on things that are planar but at a different level, it's pretty easy to fix them - use Edit > Separate to break it apart into individual surfaces, select the too tall surfaces, go to the Front view and click one time on the edit frame handle to switch it into "Scale from opposite corner" mode instead of the default "Scale from center" mode, then grab the bottom left edit frame handle and drag it upwards until it snaps onto the rail curve.

Thanks - Michael

Ah, nice to know it's a pretty painless fix for you, Michael:-)

The work around was dead easy too, so I'm a happy camper once again!

Many thanks.



Martin.

A few more rail revolves, with a clothoid and Epi- or Hypo-cycloidal speed reducer scripts:




(Also did an icosahedron using only MoI commands, mostly mirrors and rotates.)

- Brian