A randomly started discussion about the necessity of the PD single solid rule

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FBXL5
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A randomly started discussion about the necessity of the PD single solid rule

Post by FBXL5 »

adrianinsaval wrote: Fri Mar 03, 2023 2:36 pm this is why the single solid rule is so disappointing too.
Unigraphix had a single solid rule as well but dumped it a while before it was rebranded NX. I never had real trouble with too many objects in my finished part on the other CAD application. And if something unwanted appeared in the drawing it was a few clicks and the model was properly repaired; no TNP that scrambled dimensions...

When TNP is solved we might reconsider to get rid of the single solid rule.
Last edited by FBXL5 on Thu Mar 23, 2023 7:22 am, edited 1 time in total.
chrisb
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Re: #4828 PartDesign: inverse for pocket

Post by chrisb »

FBXL5 wrote: Fri Mar 03, 2023 5:36 pm When TNP is solved we might reconsider to get rid of the single solid rule.
Can you elaborate why it is so important to weaken this rule? To me it seems a very clear rule, easy to understand and there are no doubts about what a body is.
I can very well understand though, that it can be very desirable to have intermediate states where multiple solids inside of a body are allowed. But to the outside it should always be only one solid.
Example: when building a table it may be sensible to start with the four non connected legs. The outside world would then either see nothing or only a single leg until the connecting plate is added. Then the whole table would be presented as the result of the body. (I know that the example is not perfect, and that the table could possibly better be built from five bodies).
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adrianinsaval
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Re: #4828 PartDesign: inverse for pocket

Post by adrianinsaval »

chrisb wrote: Fri Mar 03, 2023 11:32 pm Can you elaborate why it is so important to weaken this rule?
it is a completely artificial limitation that offers exactly 0 benefits but several disadvantages. Can you elaborate on why it is important to keep this rule? What is the advantage? what benefit? I mean for actual modelling, not some bs about concepts.
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Re: #4828 PartDesign: inverse for pocket

Post by chrisb »

adrianinsaval wrote: Sat Mar 04, 2023 1:27 am not some bs about concepts.
Hmm, I like clear concepts, because they help me in structuring things and understand the work of others. Your post doesn’t explain to me where the benefit is, it sounds rather like, well, bs about concepts :) .
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FBXL5
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Re: #4828 PartDesign: inverse for pocket

Post by FBXL5 »

chrisb wrote: Fri Mar 03, 2023 11:32 pm Can you elaborate why it is so important to weaken this rule?
If you work on e.g. an enclosure of an electric plug you would place top and bottom side by side and finally add a film hinge between them.
Before the film hinge top and bottom are two objects that need some identical features such as fillets and chamfers and it would be helpful if they could be applied in one step on both objects. Therefore they have to be in one body.

An intermediate result could be mirrored and both halves could be extended differenly and later connected (film hinge).
I don't like to use the Part workbench for such a workflow and later return to PD.

The final result should be one object in a body, but while modelling it should be allowed to have some more objects.
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Re: #4828 PartDesign: inverse for pocket

Post by chrisb »

Thanks for sensible example.
FBXL5 wrote: Sat Mar 04, 2023 10:20 am The final result should be one object in a body, but while modelling it should be allowed to have some more objects.
+1
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adrianinsaval
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Re: #4828 PartDesign: inverse for pocket

Post by adrianinsaval »

come on you've been helping on the forum long enough to know plenty of examples, but ok
viewtopic.php?t=76482
my own example where I had to add this stupid box to make a body for a boolean operation on another body:
Screenshot 2023-03-04 100656.png
Screenshot 2023-03-04 100656.png (92.33 KiB) Viewed 2971 times
and countless others examples where this restriction is just obstructing modelling, 0 examples of it helping... FreeCAD is supposed to be free as in freedom, why is it trying to restrict how I model? IMO it goes against core values of the software.
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Re: #4828 PartDesign: inverse for pocket

Post by adrianinsaval »

FBXL5 wrote: Sat Mar 04, 2023 10:20 am The final result should be one object in a body
why? please explain what is the problem with having multiple solids, what is the disadvantage? I've asked this question many many times in the forum and nobody can give an example... but you can't go a week in the forum without stumbling upon an example of this rule obstructing someone.
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Re: #4828 PartDesign: inverse for pocket

Post by FBXL5 »

adrianinsaval wrote: Sat Mar 04, 2023 1:14 pm
FBXL5 wrote: Sat Mar 04, 2023 10:20 am The final result should be one object in a body
why? please explain what is the problem with having multiple solids, what is the disadvantage? I've asked this question many many times in the forum and nobody can give an example... but you can't go a week in the forum without stumbling upon an example of this rule obstructing someone.
It can be important for following processes. Manufacturing a part requires a model of that part and this is usually one object in a file. If a file contains more than one object it is possible for someone to choose the wrong one to be manufactured.

While a design is in progress you may stuff your document with whatever infomation, objects, satndard parts, environment data you like, but the final part to be released and filed in the database must be cleaned up.

An assembly can be built from linked single parts and it would be a pain to remove/hide some useless extra geometry in the single parts.
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Re: #4828 PartDesign: inverse for pocket

Post by user1234 »

About the topic, it is in my opinion a little bit misleading or confusing. It would better, when one times a common feature in PartDesign comes, that it differ about a full common, or a common over the given length (angle, path), the rest is untouched (add). Also since then a result can be computed, it can better pattered.

About the single solid rule, there should be a extra topic about that. I also do not like it (some parts are much better to start with a pattern), but in the end, it should (must not) give a singe solid. But i think also that this should handled by the user. But as FBXL5 said, for processing in CAD for PDM/PLC, BoM, CAM, exporting..... it is important, then a single solid (or compsolid) for a body is absolutely required. But then the users should leash on themself.


Greetings
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