Use "Snap to curve" with "planar construction" to move a CV

[timcrea]

Hello!

I am trying to move a CV in x direction (I am in "xz" construction plane) such a way this CV point intersect with the position of a curve without going onto this curve (staying in in its construction plane)

The problem is that the CV point direction does not change only in X direction, but also in Y direction because it go onto this reference curve. 

(I tried different things, but keeping middle mouse button with "snap to curve" turned on, I cannot select the curve to snap on it, and if I use lefet mouse button, the CV point go onto the curve)

In Rhino 3D, it work perfectly checking "planar" and "ortho". I hope you see what I mean! I searched on internet and the forum but did not find anything related.

LOOK AT THE PICTURE you should understand 🙂

I hope to be clear 🙂

Thank you very much!

[ravenzep]

Hi,

I can´t see why it should not work, or maybe I did not understand too well.

Can you please upload a simple file with those curves in question, so we make sure we are talking about the same thing.

By the way, forget everything you learnt in rhino, when you work in alias. They are 2 very different animals.

[timcrea]

Yes is guess, but in theory, it should be possible to do that, I also thought about align tool etc, but did not find. 

The solution would be to move each CV snapping it to the curve, then placing it to its good position, but it is very long. 

The picture shows 3 curves
Yellow: the problem to solve

red: what happening with "snap to curve" and left mouse button (while I am supposed to only move in x direction, but I did not find any solution for this)

blue: the result I would like

Sorry I cannot share a wire frame 😞

[ravenzep]

You can´t upload a file with 2 curves? Are you serious? You can recreate the same situation with 2 simple curves.

Anyway, alias can do all that you are trying to do.

Looks like i won´t be able to help anymore then.

Bye.

[timcrea]

https://www.dropbox.com/s/lbuplae06163sjh/exampleproblemsnaping.wire

Hope it works

[ravenzep]

Hi,

OK, I had a look at the file, and did what you are asking for.

It is pretty easy, here are the steps i used, and it works perfect:

I duplicated the straight line and moved it Y direction, so that i could build a simple skin surface, which will be the reference for my new construction plane.

Then I created the new construction plane (with GEOMETRY option selected). Select contruction plane command, and click on a vertical edge of the skin surface. Then align the plane to the axis you want, by clicking the little black squares on the gizmo, so basically, we want that construction plane to be aligned to the face of that skin surface. Then click SET CONSTRUCTION PLANE to establish your new coordinate system.

If you now drag the points you want, with middle mouse button and by pressing ALT at same time, the points will align to the grid, only moving in the horizontal direction.

Do it for every point, and that s it.

Job done.

Hope that helped. Good luck

[ravenzep]

A little correction to what I have said above:

The new construction plane, is not aligned with the face of that skin surface, it is in fact perpendicular to it.

Then after you have your new plane established, go to TOP view, and it will be in this view that you move and snap your CVs to the grid, moving them horizontally with middle mouse button.

Sorry for my mistake.

[timcrea]

Good it work, thank you very much for your time !!

Another question I wonder me. 
Here it works because the "reference line" is a straight curve. But imagine it is a bended curve... how would you do that? (because I guess it will happen to me^^)

In some ways: how to align CV points with a "reference curve" staying in a construction plane ?

I have readen something about snapping mode, but I don't understand if it is useful, and how to use it:
"

• If you click on the edge of a construction plane while curve snap is on, movement is constrained to that construction plane." from Autodesk Alias Help

https://www.dropbox.com/s/hn0s2aoqduzhz4t/exampleproblemsnaping02.wire

Thanks!

[ravenzep]

Hi there,

I'm glad it worked out fine.

Regarding your new question, it does not really make sense to use in this case construction planes, because the curve is not planar in any direction, so you can't really make a plane pass through that curve, it is mathematically impossible.

Another strategy should be used. You can for example use helper curves, and snap geometry to the helper curves. I see the problem you are having: by using the middle mouse button you can't really snap to the curve you want, but if you use left mouse button, it will, but you will lose the constraint to that horizntal axes. Right.. You will have to be a little creative to achieve what you want.You can use curves from curves toolbox (lines) and mark the exact points on the curve you wanna snap too , by using for example the curve section tool between the 2 curves (helper curve and curve to snap to. This way you could snap by using the left mouse button, to the points marked, or intersected between helper curve and curve to snap too.

There are 2 tools that can help you in this workflow:

1- Combine curves, which may help you to establish a curve profile in a certain desired view

2- On top right part of your interface, right next to the snap icons, there is a icon with an arrow pointing to the right. If you click this, you can establish some snapping options, especially, true snapping or snapping by projection. The names are self explanatory, but have a look at wikihelp so you make sure you understand all its power. This tool can be useful in certain situations.

It is all perfectly possible to do.

Good luck and have fun. Alias is awesome 🙂

[digiformer]

Hello Ravenzep,

every now and then i run into this problem again. Right now it happens again and looking for a solution i found this thread.

Question: See my screenshot, using your suggestion, wouldnt the CVs rather move in the direction of the "dark blue" arrows instead moving along the  cyan lines?

As far as i understood it, timcrea wanted to flatten the crv keeping the Z-position of the CVs.

At least thats my problem. The project tool is the one to solve this, but it usually produces heavy geometry.

I usually build a lot of helper-lines to achive this via simple moving CVs and snap them to the crossing lines.

It would be utterly cool if the move CV tool would have snap features also in the parallel projection mode.

Since this thread is 3 years old, maybe the 2017er Alias can do this?

See the wire (its the attached doc, why on earth is the ext. wire forbitten???) file for more info - if anyone want to help me with this. It contains the geometry shown in the screenshot below. In this case i achieved the result ( "linearc_rotate_n_Scale") via rotating and scaling the original curves. And yes i know, the curve is somewhat complex. But it pretty good  illustrates the problems and posibilities...

Kind Regards