Hi Burr,

> Is there somewhere that would tell me How you would do sweep in
> 2 portions with diiferent params for each?

Sorry I didn't describe that better earlier - to do that you would need to cut the rail curve into 2 pieces.

Then you would repeat the sweep twice, the first time picking one piece of the original rail, and then doing a second sweep using the remaining portion.

To cut the rail, select it and then run the Edit/Trim command. It will prompt you for "Select cutting objects". If you have a line or something that crosses the rail you can select it as the cutting object here, or you can also click the "Add trim points" button, which will then let you click a point on the curve to use that point as the split location.

After you have finished picking the cutting objects or cutting points, the Trim command will prompt you to "Select pieces to remove or push Done to keep all" - here just push Done (or right-click inside a viewport which is a shortcut for Done) because you want to keep all the cut-up pieces and not discard any.

So after doing that your sweep rail will now be cut into 2 curve pieces. Do sweep twice, using a different piece for each sweep and that way you can use different settings for each time you run the sweep command.

Please let me know if this doesn't make sense and I can make some illustrations.

- Michael

Very Clear, No need to illustrate this. Please when you have time, illustrate the "2 rails" sweep. I'm thinking this equates a way in my old modeler and want to be sure. ie;

Part on wall plane z.

first rail on wall plane x.

second rail on wall plane y.

???

When you have time.

I also posted a thread on our previous discussion here regarding sweeps and lofts. Please review my results!

Thanks,
Burr

http://moi3d.com/1.0/docs/moi_command_reference7.htm#sweep
(scroll)
PS You can select any numbers of profil before to choose the 2 rails
You are not obliged to put your profils on the rails! (they must be in the same plan)

Thanks Pilou. The old "look at the instructions trick". I'll mow through there a bit before I do any more irritating posts! The reference is enough for me to get started.

Thanks again,
Burr

RE: Scaling Rail

Thanks Michael.

OK - the scaling rail modifies the profile.

When would I use this as opposed to using using two rails with multiple profiles? Is this basically a shortcut to using two rails with multiple profiles?

Just trying to better understand when and where to apply the tools :)

Ed

My 2 cents ( and it is only 2) is that the sweep doesnt do well with more than a couple or few profiles. Multiple profiles would become a Lofting operation.

Eh?

Burr

Hi Ed, well you can actually use a scaling rail with 2-rail sweep as well, it's something that acts as an additional modifier on top of the basic sweep itself (either 1-rail or 2-rail).

If you find yourself trying to add a whole bunch of cross-section profiles to a sweep to try and control the side-view profile of it, that can be a good sign that you should be using a scaling rail for that instead.

Here's an example of that from a while ago:



You can kind of get the idea there that someone is trying to make the sweep fit to that guide curve that you see running along the upper part when viewed from the side.

But it can be frustrating to try to get the shape to match purely by adding more and more and more profiles, you may have to add quite an awful lot of them to control the profile and that tends to be a lot of work.

That's what a scaling rail will handle for you - it will pull those profiles up so that they match that additional "scaling" rail going down the center so you don't have to try and add many many profiles to try and get more direct control over the side profile.

Also, a one rail sweep with scaling rail is not quite the same process as a 2-rail sweep.


A 2-rail sweep works something like this - if you have 2 rails with a profile curve:



The profile will be moved by incrementally sliding it along each of those rail curves, so it will draw out a path something like this:



So one thing to note here is that the profiles are not necessarily always perpendicular to any one single rail curve, like here is a more exaggerated example:



You can kind of get an idea there how the profiles kind of slide around for 2-rail sweep. If you want something that is guaranteed to be a perpendicular construction off of a single backbone or spinal-column type curve, then one rail sweep will do that - it will move the profile curve along that spine curve and be perpendicular to it at every spot.



With 2 rails it just is not physically possible to be perpendicular to both rails at the same time at every spot unless your curves happen to be offset curves from one another.

Now when you use a scaling rail with a 1-rail sweep, it keeps the perpendicular-to-spine type arrangement and then will shrink or expand those profiles still in the perpendicular direction. So for example if this is the scaling rail that is added to that one rail sweep:



The profiles will get then expand in this kind of manner:



So one-rail sweep with scaling rail does not "slide" the profile along the scaling rail, it only slides along the spine rail and then grows to intersect the scaling rail, that's what is different about it from 2-rail sweep.

Hope this helps!

- Michael

Hi Burr,

> My 2 cents ( and it is only 2) is that the sweep doesnt do well with
> more than a couple or few profiles. Multiple profiles would become
> a Lofting operation.

It all kind of depends on what areas of your result you want to have control over.

If you want something that has a kind of automatically calculated "tautness" in one direction, then Loft should work well for that.

Like for example if you take these 3 circles:



A loft will build a shape like this:



It's sort of passing through those shapes in a kind of minimal smooth way.

If you wanted to control more details of how it is shaped as it is marching along in the "lofting direction", then a sweep will let you get more control over how the sides are shaped, like for example:



You could get that with just doing Loft by adding in a whole bunch of circles, but it is easier to draw a curve to use as a rail for sweep to get more control over that.

If you need additional shaping control, then use sweep, otherwise if you don't need exact control over that side shaping, then Loft is more likely the way to go.


(By the way, for doing things made up of all perfect circle sections actually doing one profile and using revolve is easiest for that, but still this example should show the right idea I hope).

- Michael

Getting back to the first post, here is my versionof the Pilou Top Hat.
Brian

Thanks Michael, good explanations.

One thing that can be tricky is if the scaling rail doesn't go past the profiles, then you can get a sharp kink. Just wanted to mention that.

Oh.
- wasn't there a way to capture the viewport image? (I'm using my fathers old pc here and it doesn't have any photoshop or anything, so printscreen won't do.)

-Fredrik

Hi Fredrik - right the scaling rails are expected to run the entire length of the sweep, and it doesn't hurt any to actually extend them a little further past the ends even just to make sure they cover the full area.

If an area is not covered by the scaling rail it will basically revert to "regular sweep" in those areas which is kind of a very sudden shift in shape which isn't good.


> - wasn't there a way to capture the viewport image?

It is possible to set up a script to do it, but actually probably your father's old machine still has the creaky old Windows paintbrush which will do the job for pasting and saving a jpeg file. Try Start/Run and then type "pbrush", and try not to laugh.

Please let me know if that is not working and I can cook up a MoI script for you for doing it.

- Michael

Hi Michael

Scaling rail is neat, I haven't seen this before in other CAD software.

Yes, the good ol' machine has paintbrush:)

Whish:
view capture (since its effective for communication of ideas, it ought to be always fast to do)

Ok, when you go to File>Export, there you could have PNG file option that saves the current Viewport as a PNG.
It wouldnt lead to any more buttons or anything.

-Fredrik

Hi Fredrik,

> Scaling rail is neat, I haven't seen this before in other CAD software.

Thanks! :) Yes, as far as I know MoI is the only one that has it.


re: view capture by File / Export - that's definitely a good idea, I have added it to the wishlist. A few questions kind of pop up for it though, like for example Export is actually short for "Export selected", which lets you write out only the selected objects to a geometry-based file. But I guess for saving to an image it would not do just selected objects... that would sort of be mixing the meanings up a bit, but maybe that is not a big deal.


In the meantime, here is a script that you can use to save a screenshot out to an image file by using a shortcut key, without needing to run any other program. To set it up go to Options / Shortcut keys, add in a new entry with whatever key you want to trigger it, and add this in as the Command part:

script:var img = moi.view.screenshot( 'viewpanel', false ); var name = img.getSaveFileName(); if ( name != '' ) img.save( name );

- Michael

>Thanks! :) Yes, as far as I know MoI is the only one that has it.

There are couple of small (and big) things in MoI which you dont't find anywhere else. That's a good achivement, its not just different; its different and useful, :)
I'm using moi right now to sketch out some ideas about a bicycle seat, and since it's portable i can do it at my dad's pc.

>re: view capture by File / Export - that's definitely a good idea, I have added it to the wishlist. A few questions kind of pop up for it though, like for example Export is actually short for "Export selected", which >lets you write out only the selected objects to a geometry-based file. But I guess for saving to an image it would not do just selected objects... that would sort of be mixing the meanings up a bit, but maybe >that is not a big deal.

True indeed
You could concider to have a new button in the View Tab too, it would be the most "logical" place I guess. There is just space for one more button there, but you might have reserved this space for something else? ...If you did use a whole new button for Screen Capture though, you might concider to have other associated things like "Print to scale" in its window., (hehe another whish there..)

>In the meantime, here is a script that you can use to save a screenshot out to an image file by using a shortcut key, without needing to run any other program. To set it up go to Options / Shortcut keys, add >in a new entry with whatever key you want to trigger it, and add this in as the Command part:

wow! that's perfect :)

-Good summer!