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2D Loft Problems

Stuart

Senior Member
Hello,

I haven't used loft before, so I decided to try a simple loft with a 2D guide. I ran into 2 problems.

  1. The loft is not symmetrical like the examples in the videos. They look very similar, although the examples have a 3D guide. How do I get it to make the loft symmetrical?
  2. When I edit the loft, the sketches to loft are gone and I have to add them back to the list. The loft status says no errors.

What's wrong?

upload_2020-5-11_9-52-20.png

This is what happens when I edit this loft

upload_2020-5-11_9-53-14.png
 

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  • 2D Loft.AD_PRT
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Stuart

Senior Member
4 guide curves is needed

Are 4 guide curves always needed? Is it because there is a 4 sided sketch in the loft?

I can't find any help on the guides. I looked at every reference to "loft" in the help. It only says "multiple guide curves can be used." The video only shows one. If I'm understanding it properly, Global means use the guide curve for the whole loft, Local means use it near that guide curve. Correct?

Is there help that explains how and where to use guides?
 

GIOV

Alibre Super User
Hi Stuart,
Only you need apply "minimize curvature" and your loft will be ok.
upload_2020-5-11_22-20-59.png
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  • 2D LoftGIOV.AD_PRT
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bigseb

Alibre Super User
I've found it's best to just avoid lofts to avoid the headache. The 3d modeler MOI was once bundled with Alibre and I've heard nothing but good things about it for organic and curved shapes. http://moi3d.com/
Moi FTW.

It should also be said that this is a terrible shape for lofting. Round to sharp corners to round... bad idea.

BUT!!

This is the same model lofted in Moi. No guide curves, just the 3 basic shapes. In Moi you have a lot more control over lofts with just basic shapes. If you were to add guide curves then you'd use the sweep feature. Then you could also use blends, n-sided or network functions to give absolute control over your shape.
 

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  • lofty.AD_PRT
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JST

Alibre Super User
I also avoid them wherever possible.

Other issues with loft in Alibre include:

1) they are apparently not "real" surfaces, many commands do not seem to work with the results, as if (as may be the case) there is no actual geometrical definition of the curves, and they are generated on the fly, on demand.

2) Even with guide curves, the final result often "bulges out" between curves, as if the program were trying to shape a balloon by tying ropes around it. That may be inherent to the way lofts work. I would have expected the loft to "fair" the surfaces through each guide curve or outline, but it often does not, and the "minimize curvature" often does not fix it..
 

GIOV

Alibre Super User
Hi Stuart,
I forgot the guide in my previous comment. You need only to apply type"local"
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  • 2D LoftGIOV.AD_PRT
    476 KB · Views: 1

GIOV

Alibre Super User
Moi is very restrictive. Don't have engineering capability like Rhino or SolidThinking or pilot.
 

bigseb

Alibre Super User
Moi is very restrictive. Don't have engineering capability like Rhino or SolidThinking or pilot.
Wouldn't say Rhino is an 'engineering capable' software. More importantly... cost. For $295 (£241) you get a TON of design functionality. Rhino costs €995 (£880).

If anyone needs to create complex shapes, work with surfaces or repair files that AD can't then Moi is perfect.
 

GIOV

Alibre Super User
I disagree with you bigseb
For Engineering scope it has add-on like RhinoMarine or Rhino parametric and is super more effective and cost less than Alibre. I have hope in AD but still is so poor in everyday productive software.Moi is insufficient. Only shapes and the ex-Rhino Michael Gibson.know that.
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bigseb

Alibre Super User
I disagree with you bigseb
For Engineering scope it has add-on like RhinoMarine or Rhino parametric and is super more effective and cost less than Alibre. I have hope in AD but still is so poor in everyday productive software.Moi is insufficient. Only shapes and the ex-Rhino Michael Gibson.know that.
Apples and oranges. Moi isn't marketed as an engineering package. A snip from the website:
MoI’s sleek intuitive UI blends a fluid easy workflow with powerful tools, making it the perfect choice for someone who has been frustrated with the complexity of existing CAD tools.

MoI is also a fantastic complementary tool for a polygon-based artist since its CAD toolset and advanced boolean functions enable extremely rapid creation of mechanical or man-made type “hard surface” models. The icing on the cake is MoI’s unique polygon mesh export that generates exceptionally clean and crisp N-Gon polygon meshes from CAD NURBS models.

Got a tough shape to model? Moi is by far the 'easiest to use' tool there is.

By. Far.

As far as engineering tools go... Catia, Creo, NX, Solidedge, Solidworks, Inventor AND Alibre are miles ahead of Rhino in terms of being an engineering solution. Have you seen the state of Rhino's drawings? Talk about a non-associative waste of paper. Or how about the non-ability to create BOMs. That model of the ship... looks pretty eighties tbh. And is that Jeremy, James and Hammond on board?

Not saying Rhino is bad. Its good software, provided you stay within its limitations. Can you design a boat or an injection mould or a coal-fired power plant in Rhino? Probably. Is it the best tool for that sort of work? No. Neither is Moi, but that was never its claim.

FUN FACT: McNeel originally specialized in writing add-ons for CAD software before buying then-employee Michael Gibson's code for a CAD program. This code became Rhino. Michael then left McNeel to focus on his own software which is now called Moi. If anyone know the limitations of both Moi and Rhino it's Michael Gibson.
 

bigseb

Alibre Super User
I believe you. At the end of the day we use what we have. But its still not the best tool for the job.
 

bigseb

Alibre Super User
Looking at the OP's post again...

No-one's mentioned the tangent capablity. It is entirely possible to do this without any guide curves, in AD, by simply adding a tangent to the middle profile. That way the loft doesn't extend beyond the profile. Thus:

0001.JPG

0002.JPG

Play around with the settings.
 

Attachments

  • lofty2.AD_PRT
    357 KB · Views: 1

HaroldL

Alibre Super User
No-one's mentioned the tangent capablity. It is entirely possible to do this without any guide curves, in AD, by simply adding a tangent to the middle profile.
Yes the Tangency options are nice but without a consistent result they are hard to master. I recently had a Loft issue and was told by support that Magnitude was dependent on and needed an Angle (if I am recalling correctly). That seems counter to what I needed because I needed the Loft to be Normal the the first sketch, which I understand is Angle =0, and was being told to add an angle to my loft. There needs to be a more descriptive "Help" on the use if the tangency functions in loft.
 

DavidJ

Administrator
Staff member
Harold - in that support case all profiles were identical and parallel (but translated), it was a very unusual case of a loft so it had some odd behaviour. As you might recall, the answer was to use a different tool.
 
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