Datum entity vs Body

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dbecad
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Re: Datum entity vs Body

Postby dbecad » Wed Jul 18, 2018 9:58 pm

If i understand the GP issue, it would be how can we share a datum plane between bodies?
The possibility to define one plane and then use it in multiple solids could be useful.
What is the current way to do it right now?

I have tried to move it to a part and link it the the part's origin but somehow it fails. I tried to add the first plan to a shape binder in the second body but then how to use it?

Creating another plan then attaching it to the first (and using cross reference choice) does "work", but generate a warning (PartDesign::Plane: Links go out of the allowed scope) each time I move the original plane.
datumShared.png
datumShared.png (46.12 KiB) Viewed 270 times
Also this seems to be a bit clunky and I understand that ideally like any dimension, it's preferable to not duplicate anything.

So how to do it properly?

Edit:
Would allowing datum object to be created and linked to parts origins work?
It would respect the parent-child links, and bodies in this part could reference the datum?

thanks
Cheers

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Pauvres_honteux
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Re: Datum entity vs Body

Postby Pauvres_honteux » Wed Jul 18, 2018 10:31 pm

Hmm, @DeepSOIC; are we talking about the same thing here?
In my world a Part = file (an undividable thing like a cylinder head).
Inside this part there are Bodies, a lot of them.
Inside the Bodiea are solids, which can originate from an extruded sketch, thickness of a surface, surface cut of a primitive(block) and so on.
The top Body = PartBody witch contains all other bodies.

One can not move the Part inside it self since it's a file.
Ofcourse one can move Bodies inside the Part, but there's no use in that since one do move its content via points, lines, curves, planes and surfaces.

Points, lines, curves, planes and surfaces are the basis for all solids and they are common for all solids as well, as far as it's possible anyway.

If anyone thinks "what about assembly then?" I say an assembly is a separate file pulling other Parts into it and arrange them, i.e. you move Parts inside an assembly. I think all this has been confused by most people since Jürgen stopped visiting this fora. Man, I which he could get back and explain all this, he is so much better than I am at expaining this.

As it stands now it's a total mess regarding the FreeCAD document versus FreeCAD Part versus FreeCAD Assembly.
In my world one either load a FreeCAD Part or a FreeCAD Assembly. The general FreeCAD document must go, at least as an abbrevasion.

@dbecad; you're on the right track there. But this is just the first of many, many steps in this direction. In the end one can rule an extremly complex model with just a few key "features". This is how we all do it in the professional world.

But we take it one step at a time. I'm very happy that DeepSOIC took his time and fixed so the datum point now works, really appreciate that!
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DeepSOIC
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Re: Datum entity vs Body

Postby DeepSOIC » Thu Jul 19, 2018 12:45 am

Well, to some extent that was how it originally intended to be. Body was not moveable in the early days of PartDesign Next. So there was none of that coordinate system barrier, and allowing datum features in Part rather than Body would have been much easier.

Actually if you just don't let yourself move bodies, there is technically no barrier. It was just programmed with this "all information used to make a body must be in that body" way of thinking. And I'm not against it, but having datum lines and planes and points and sketches in Part for reuse in multiple bodies, is also something I would find useful. it gives more freedom, more flexibility.
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DeepSOIC
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Re: Datum entity vs Body

Postby DeepSOIC » Thu Jul 19, 2018 12:48 am

Pauvres_honteux wrote:
Wed Jul 18, 2018 10:31 pm
In my world a Part = file (an undividable thing like a cylinder head).
There is no strict meaning of what Part is at this moment. Part is what it is, a moveable container for anything, that is just not very well supported yet. Just learn what it does and what it does not, and use it all to your advantage :twisted:
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DeepSOIC
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Re: Datum entity vs Body

Postby DeepSOIC » Thu Jul 19, 2018 12:55 am

Pauvres_honteux wrote:
Wed Jul 18, 2018 10:31 pm
Part = file (an undividable thing...
I'm afraid that's a definition of a solid. A general part, at least for me, is some unit of utility, or a unit of assembly. It can be just a solid, but it can be an assembly internally. E.g. an extruder of 3d printer. I hope everyone would agree that in a 3d printer, it's a part, especially if there are two extruders.
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NormandC
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Re: Datum entity vs Body

Postby NormandC » Thu Jul 19, 2018 1:08 am

Pauvres_honteux wrote:
Wed Jul 18, 2018 10:31 pm
In my world a Part = file (an undividable thing like a cylinder head).
Inside this part there are Bodies, a lot of them.
Inside the Bodiea are solids, which can originate from an extruded sketch, thickness of a surface, surface cut of a primitive(block) and so on.
The top Body = PartBody witch contains all other bodies.
You are describing CATIA. In my own world, what you just wrote above is meaningless.

I for one do not want FreeCAD to become a CATIA clone.

I feel that most of the complaints and wishes we see here and that come back over and over are in good part caused by the single-solid limitation in the PartDesign Body. And it's been written that this limitation may be lifted in the future. ickby also mentioned he wanted to allow more reference objects in Bodies. But there is nobody anymore working on PartDesign so we'll unfortunately have to be patient and hope for someone to pick up its development, because it need it.
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saso
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Re: Datum entity vs Body

Postby saso » Thu Jul 19, 2018 6:30 am

I am of course supporting Pauvres_honteux arguments since they are mostly the same as what I have been arguing for in the past months

https://forum.freecadweb.org/viewtopic.php?f=8&t=26357 full topic
https://forum.freecadweb.org/viewtopic. ... 40#p223582 and several posts after it
https://forum.freecadweb.org/viewtopic. ... 70#p237682 and several posts after it

And this is not about how Catia works but about how all history-based cad modeling programs that support bodies work, so this are at least all of this Catia, NX, Solidworks, Soildedge, Inventor, Onshape, Fusion 360 and probably a few more less known ones. Indeed Creo does not support bodies, but the difference in the general structure of the model is actually not that big if you have bodies or not. Assembly and Part containers are still the basics of the hierarchy of models in all of this programs.
dbecad
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Re: Datum entity vs Body

Postby dbecad » Thu Jul 19, 2018 3:32 pm

saso wrote:
Thu Jul 19, 2018 6:30 am
what I have been arguing for in the past months
Thanks Saso, that was a lot more argumented than my half baked example, I guess I missed this thread, good read :D
Cheers
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Pauvres_honteux
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Re: Datum entity vs Body

Postby Pauvres_honteux » Thu Jul 19, 2018 7:41 pm

saso wrote:
Thu Jul 19, 2018 6:30 am
I am of course supporting Pauvres_honteux...

... this is ... how all history-based cad modeling programs that support bodies work. ... Assembly and Part containers are still the basics of the hierarchy of models in all of this programs.
Finally! There are more of us out there!
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Pauvres_honteux
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Re: Datum entity vs Body

Postby Pauvres_honteux » Fri Jul 20, 2018 8:33 am

Yesterday I got a sinking feeling in my gut after I reread this topic a few times.

Could it be that there are coorporate moles in our community? Constantly nudging and poking the development in a direction away from the big fives market?
I mean continuing on this road will utterly stop in a dead end ally. And that would serve the biggies really well, getting rid of all mid-level competition AND stopping the only real threat there is: FreeCAD. They would increase their market and be king of the hills, unthreatened for the foreseeable future.

Doing it the proposed way we would sweep the court clean, leaving no traces of any competitor.

Another thing came to mind; do we have any assembly functions that can load files and 3D-arrange them in a separate file?