Hi Pilou,

> Because the flat curves must will be curvated again!

No, they don't have to be manually curved - they stay planar and then are used to trim the surface.

That will generate a curved edge on the surface where it is intersected by the planar trim curve projection. That's all built into Trim, you just cut the surface (after untrimming the surface to prepare it for new trimming) with the planar curves and that's done.

- Michael

Hi Pilou,

Attached here is a cleaned up version that has that messy overlap area fixed and simplified, this one will shell.

- Michael

Ah damned!
It's for that something was curious when I Offseted the curvated curves there were a little difference!
Straight horizontal bottom will be not horizontal after the mirror!

So with your surface the shelling works but there is a little problem :)
Shelling is "vertical" 90° to the normal !
Or the original bottom edge is inclined ;)

Hi Pilou,

> Shelling is "vertical" 90° !
> Or the original edge is inclined ;)

Yeah, if you want a constant thickness throughout a piece, that's how it works!

The original piece also has pieces that don't line up with one another, do you want to keep that as well? :)

You could also do an Extrude of that surface that I posted previously instead of a Shell, does that give more of the desired result? It looks like that may be more of what was intended here since one side is nearly straight up vertical.

- Michael

So for example with Extrude you get this kind of result:





That seems to be the kind of edge arrangement that you might want.

But just be aware that extrusion of a curved object in one set direction does not actually create something that has a constant thickness throughout the piece.

Here's an example where you can see this more clearly - here I have a curve and then a second copy of it a small distance vertically above it. This is like extrusion, and you can see that the thickness is not equal in all areas:



When there is less curvature it becomes more difficult to see it clearly though.


It's only shelling or offsetting that creates things with constant thickness everywhere, unless the thing being extruded is planar in which case extrude is equivalent to shell.

- Michael

Yes :)

I have now the original good half-surf that must be "extand" by 2 units
Edge Bow and poop are inclined!

I try to extract and offset the curvated curves but that is not always success!

Hi Pilou,

> I try to extract and offset the curvated curves but that is not always success!

For which step do you not have success? The copying, the flattening, the offsetting?

I just tried doing it on your model over here and did not see any problems...

If you have a problem with an offset for example, could you post a model file with the particular curve that you are trying to offset?

Also I would still recommend to delete everything instead of one surface and work from there, then extrude the final result to get the solid.

- Michael

you can't extrude because bow and poop are inversed inclined!

Hi Pilou, attached here is a finished result.

> you can't extrude because bow and poop are inversed inclined!

Then simply do an extrusion which creates the proper edge direction in the back, and slice the result with a line in the front to cut it to the desired angle.

The attached result is an extrusion so you may need to cut it with a line (since it is a solid use the boolean difference for cutting it) to get the proper angle. But other than that it seems to be all set up.

The untrimmed original surface was not quite large enough to cover the offset curves completely, so I extended it by adding a tangent line to either side and extruding it.

- Michael

Hi Pilou, also of course if you wish to make adjustments, it is easier to preserve the original curves, either hidden or saved to a different file or something. That then eliminates the need to extract them to recreate them.

Also it's good to know how the original was created, like is it a shell, is it an extrusion with a piece cut off of it, and so forth...

All that information from the original creation makes it easier to reconstruct the model later.

- Michael

cross post :)

Hi Pilou, in your last post there it looks like you have forgotten the flatten step.

Switch to a side view (either Front or Right) and flatten those curves to a single plane before offsetting them.

Although it is possible to offset a curve that is non-planar and bending around in 3D usually you do not want to do that because you won't get the corners between pieces to be extended and matching like it will happen in the 2D planar curve case.

So that's your problem - you skipped the flatten step from what I see there.

But did you see my previous post that has the completed model in it?

- Michael

< so I extended it by adding a tangent line to either side and extruding it.
Yes but it's a line and not a curve? no problem for a close up but in theory?
Function Extend make the same ? add a tangent line to a curve from last 2 points of the a curve?

For have the original I must cut incline ;)

But you agree all that don't arrive if original generator were keept!

I have a trouble: how do you make the the curvated surface after make the "flatten" curves and offtseted them?
I miss something :) A simple extrude and use old curves?

Hi Pilou,

> I have a trouble: how do you make the the curvated surface
> after make the "flatten" curves and offtseted them?

That's by doing an "Untrim" on one of the original surface pieces.

Take one of the original curved surfaces, delete all the other ones, use Edit/Separate so you are dealing with just a single surface.

Now select all the edges, and hit delete to remove them and recover the full underlying surface - that's how I got back the original larger curved surface to trim.

The original is wide enough in one direction to cover the new larger outline, but not in the other direction where I added the lines.

- Michael

Hi Pilou,

> Yes but it's a line and not a curve? no problem for a close up but in theory?

It's only a problem in theory if you want some other shape than a straight extension there...

You would need to know what the intent is of the extended shape - should it extend in a straight way from the current one? If so then a line would be the correct shape for that because a line is straight.

Just because it is a line does not mean that it is automatically bad for all cases.

It would probably not be quite as good if it was a polished mirror or something reflective like that but that does not look to be this particular case. In reflective objects things like lines tend to be more visible to the eye.


> Function Extend make the same ? add a tangent line to a curve
> from last 2 points of the a curve?

Yeah, same as what extend will currently do.

For just placing a line I usually just draw a line and use Straight snap to lock on to the tangent line.

- Michael

Hi Pilou,

> For have the original I must cut incline ;)

So yes, go ahead and cut it then! :)

There is no rule that you must only accept the result of an extrude and cannot modify it by cutting.

It cutting is necessary, then draw a line and cut it...


> But you agree all that don't arrive if original generator were keept!

Yes, not without an additional cut - that means to draw a line in and do a boolean difference to slice it at the angle you want.

I'm not entirely sure if the actual desired shape is an extrusion with a cut end though, or a shell with a cut end.

Normally to get constant thickness you use shell, but since this is not heavily curved the difference is pretty small for this case.

- Michael

< Now select all the edges, and hit delete to remove them and recover the full underlying surface - that's how I got back the original larger curved surface to trim.
that's this! I have tollally missed this paradigmatic thing!!! It's an Earthquake for me! :)
From what comes the measure of the length? I have only half of the form!

A process ;) Flatten must be made in FRONT FACE !!! (and reading begin by the Bottom to Top sorry :)
@Michael : I don't use the extrude method in case where all sides should be inclined (so to much cuts)
As I obtain 2 surfaces I can easily make a sweep 2 rail between them even inclinations :)

>Then go to the Front view and use the edit frame to flatten them down to be planar

Wow, how did I miss this feature of the edit frame? Another example of MoI's understated brilliance. :-)

Jesse