Thanks Michael

Getting clearer all the time. I think, the more one understands the inner workings of the software, the better modeler one can be.

Part of my background is in crystallography so my concept of a solid is tainted (?) with ideas of a space bounded by connected smooth faces and packed full of atoms!

Hi Michael T.

I have noticed that when exporting from MoI to Alibre (as stp), Alibre does not appear to recognise circles, I mean for the purpose of dimensioning radii. Is this true? Perhaps they are just seen as curves as opposed to circles??

Steve

Hi Steve,

I think that's right. I'll check it out. I think any indirect file transfer type breaks entities down that way, i.e. curves versus circles, lines etc.

I'll let you know if I find anything else out.

Michael T.

Hi Steve - yeah it looks like currently when MoI writes the step file it writes the circle as a spline curve type.

Often times if it is important for a receiving application to handle circles in a special way, they can check to see if the spline curve is the standard kind of spline curve that makes a circle, and flag it as being a circle primitive at that point. But it sounds like Alibre is not doing that kind of shape detection in it.

Could you please post an example file with a circle in it saved out from Alibre so I can see how it prefers to have circles structured in the STEP file? I'm not sure yet if I will be able to do much about that but it may be possible for me to adjust that.

- Michael

Hi Steve, can you give the attached file a try in Alibre and see if it can recognize it any better or not?

This one is still written as a spline curve, however it has a flag set on it that tags it as a "CIRCULAR_ARC" type form.

If that seems to work better and helps Alibre to recognize it as a circle, that could be an easy adjustment for me to make.

However, it may not do the trick because Alibre may want a full "circle primitive" definition instead. Currently the library that I'm using for exporting to STEP format does not handle that so that one would take a while longer.

- Michael

Thanks for that Michael T. It does seem to be the case.

Michael G, I could not get Alibre to see that test_circle.stp file at all. I tried various import options but nothing showed up on the display.

And here is an stp file with lots of circles, saved out of Alibre.

Good luck!

Steve

Hi Steve,

> Michael G, I could not get Alibre to see that test_circle.stp file
> at all. I tried various import options but nothing showed up
> on the display.

That one was a circle curve, when you mentioned circles previously I was thinking you were talking about a circle curve like you would draw with the Draw curve / Circles / Center command in MoI.

But from your example it looks like you are more interested in circles that are edges of solids.

For reading the curve into Alibre, I'm not sure how that works exactly, but you may need to do some command like "import sketch" or something like that to read curve data in (rather than solids).


Just one other test to make sure I understand what is happening, do you also get the same problem with the additional cylinder_test.stp attached here?

And can you create a minimal cylinder object like that (with nothing else) in Alibre and post that here for me to compare with?

I think that the STEP library that I am using does not have this function in it to write out circle entities instead of spline entities, so there may not be anything that I can do about that immediately. But I have sent an e-mail to the author of the step library to ask if he can include that function in the future.

Thanks,
- Michael

Hi Steve and Michael G.

Here is a PDF file from Alibre's design guide regarding import and export for Alibre Design 10.

Hope it helps. You can download Alibre's complete user guides from the web site.

I don't want to clutter up Michael G.s forum :-)

Michael T.

Hi All....

Below are the test result :

Hi Michael T, thanks for posting that - unfortunately it doesn't seem to cover technical details like what kinds of entities are recognized as circles...

When you import into Alibre, there are a variety of import options including things like "Heal solid", you might try enabling those options to see if that will make Alibre recognize the circles or not.

- Michael

Hi All

Michael still no go with your cylinder_test file.

Just to clarify, my interest here is in being able to take a model from MoI into Alibre and use the "create drawing" feature with dimensioning, annotation, etc.

Anis' result is the same as mine. In Alibre's drawing window, the dimensioning utility should recognise the circle and dimension it as it does in SoidWorks. But it doesn't happen. It is the same in the 3d window of Alibre...one should be able to dimension circles there too. Lines are no problem .

I tried quite a few import options without success.

Here is a cylinder object made in Alibre. There are options to export 3 diff types of stp file, I just picked one.

In MoI when one makes a cylinder by extrusion, it is customary to delete the original circle, whereas in Alibre the original circle remains as an editable object. So I also tried extruding a cylinder in MoI and not deleting the circle. But Alibre would have none of that and refused to even open the file.

I will keep playing around as and when I have time. But, Michael, please don't loose sleep over it!!

Hi Steve, I've talked to the author of the STEP library that I'm using and he says that it should not be very difficult to enable an option to write out circles as "circle" entities instead of as more generic "spline" entities. I'm not exactly sure when that will be complete but it is somewhere in the queue now.

However, he also mentioned that there is an option for this that can be enabled currently for IGES export.

I've attached a test file that sets that option.

Can you please see if this cylinder_test.igs file works better for dimensioning in Alibre?

If so then that is one thing that will be easy for me to set up for the next v2 beta, and that could be an option to get it done until the STEP equivalent is ready.


> So I also tried extruding a cylinder in MoI and not deleting the
> circle. But Alibre would have none of that and refused to even
> open the file.

That seems to be a particular quirk of Alibre - other programs seem to deal with curves present in a STEP file as well as solids... If they don't want to read in "stand alone" type curve data, they should just skip them instead of failing the whole import. I think that one is something that they will need to fix up in Alibre.

- Michael

OK great news, Michael

With your igs test file it is possible to dimension circles in 2d drawing mode.

Also, in 3d mode, Alibre recognizes the cylinder edge as a circle.

So that seems like the solution. I don't think it really matters to many people whether they export from MoI as stp or igs.

Thanks:)

Hi Steve, that is great news!

So for the next beta the IGES export will be tuned up to do this by default - it will export lines, circles, and arcs as those specific kinds of entities in the IGES file instead of as generic splines.

If it causes any problems (not likely but just in case), it will be possible to turn that off and return to the old behavior by editing an entry in the moi.ini file:
[NURBS Export]
WriteAnalytics=y

Later on at some point this will happen for STEP as well.

- Michael

Thanks again Michael, that will certainly be a valuable feature!

Very cool Michael G.!

Good luck Steve!

Michael T.

OK here's a funny thing.

Even with the current igs export set up in MoI (V1.0 and V2.0 beta) Alibre can recognize circles!
So I guess nothing really needs to be done:)

Steve

Hi Steve, well that's interesting! I wonder why they detect circles only for IGES and not for STEP format...

So anyway, that's great, you can get your stuff working right now even before the next beta is out.

I think I will leave the new "simple entity" stuff enabled anyway though, maybe it will help some other programs to recognize them.

- Michael

is this problem of detecting circle in Alibre of imported STEP file resolve yet?

I have several solid models in MOI which i want to constraint it in ALibre. already export is as STEP so that alibre can import it as assembly of several parts.

if i have to export it as IGS in MOI, then i have to export the solids one by one and import it again one by one in Alibre.

Hi Bud,

> is this problem of detecting circle in Alibre of imported STEP file resolve yet?

I'm not really 100% sure - but this discussion thread is 4 years old and I don't think that it has been mentioned as a problem for quite a while now. So it's possible that it has been tuned up in the Alibre STEP importer since then.

I don't know for certain though, I'd recommend testing it yourself with one of your specific models to make sure it does what you need.

If it does not work correctly, try going in MoI to Options > General and push the "Edit .ini file" button and go to the [NURBS Export] section and set:

[NURBS Export]
WriteAnalyticCurves=y
WriteAnalyticSurfaces=y


It kind of looks like the circle case for analytic curves is still not handled in the import/export library, but it does seem to be active for surfaces, with a cylinder then getting written out as a specific cylinder surface entity in the generated STEP file and not as a generic NURBS surface. That could possibly help if Alibre is not recognizing the surfaces as cylinders automatically itself.

- Michael