Reference(Datum) Line through sketch circle center?

[chrisb]

One question not answered -- is one not allowed to use the renamed object (Label) for references? One can do this with constraints, but it doesn't seem to work for objects.

What did you try? It works as always in expressions with something like <<myLabel>>.Placement...

[garya]

I must be hallucinating; it seems to work fine now in the properties tab. However, I cannot select a Datum line as external geometry in a sketch from another body. In the attached file, editing sketch Sk_B2_Blk, I can't make an external geometry selection of Binder_B1_Hole_Ctr. However, if I activate Body (My_B1), I can get at the original reference line DatumLine (Ref_B1_Hole) in a sketch in My_B1.

[chrisb]

External references are something different. You need a ShapeBinder to transport geometric information from one body to another. (Didn't look at ypur example yet).

[garya]

External references are something different. You need a ShapeBinder to transport geometric information from one body to another. (Didn't look at ypur example yet).

It has a shape binder, which is why I don't understand what's going on. Furthermore, while I can make the actual DatumLine appear and disappear by selecting it and using the space key, I cannot get the ShapeBinder line to appear at all.

[chrisb]

I looked at the model and understand now. You have a ShapeBinder of a DatumLine, and you are right, it is not visible and thus cannot be used for external references.

Edit: corrected previous text.

[garya]

I looked at the model and understand now. You have a ShapeBinder of a DatumLine, and you are right, it is not visible and thus cannot be used for external references.

Should this be considered a bug? If so, I'll file one.

[chrisb]

Should this be considered a bug? If so, I'll file one.

Not sure if it's a bug or a feature request. I can only think of Werner to answer this.

pinged by pinger macro

[wmayer]

If you hover over the object of the other body you will see a message in the status bar why it can't be added as external reference.
This object belongs to another body, can't link

I can't remember the exact details but referencing geometries of another body is not allowed any more because you can easily break your model. Maybe ickby does because he once has implemented this behaviour.

For a while it was possible to ignore the restriction by pressing a certain shortcut but this way has been removed in the meantime, too.

EDIT:
The original restriction to not allow cross coordinate-system links was discussed in epic length here: https://forum.freecadweb.org/viewtopic.php?f=10&t=20749
In another thread it was explained in the context of sketches what might break: https://forum.freecadweb.org/viewtopic.php?f=3&t=24728

[garya]

If you hover over the object of the other body you will see a message in the status bar why it can't be added as external reference.
This object belongs to another body, can't link

I can't remember the exact details but referencing geometries of another body is not allowed any more because you can easily break your model. Maybe ickby does because he once has implemented this behaviour.
EDIT:
The original restriction to not allow cross coordinate-system links was discussed in epic length here: https://forum.freecadweb.org/viewtopic.php?f=10&t=20749
In another thread it was explained in the context of sketches what might break: https://forum.freecadweb.org/viewtopic.php?f=3&t=24728

Those discussions are from 2017 and 0.17. This seems like it invalidates the whole concept of a shape binder. Is that correct? I have shape binders which are (were?) working fine in 0.20 and were working in 0.18 and 0.19. Am I misunderstanding what you're saying?

[chrisb]

This object belongs to another body, can't link

The issue here is a different one. It concerns only datum geometry. It is possible to add a ShapeBinder of a DatumLine or DatumPlane to another body.
These are correctly created as far as I can see ...

SnipScreenshot-688b4e.png (40.31 KiB) Viewed 1845 times

... but they are invisible and thus cannot be selected for external references in a sketch or for padding up to face for a pocket.