What Compound parts are made for?

[plgarcia]

Hello
Can somebody tell me or point me the documentation page if available that explain what compounds are used for, what functional difference with cuts and what gain is expected.
The problem is that compounds do not work completely.
Here are some cases they do not work:
- Fusion of two compound (In my test leads to black objects)
- Cuts of two compound (result unpredictable)

Probably most of operations are not implemented and do not work.

As far as I understand, a fusion should be made with the components of the compound before being used for further operation. If so it is just deferring the fusion operation! Am I right?

I have the feeling they are not usefull and could be replaced by fusions!

If you want an example I can build one.

[triplus]

Hi @plgarcia.

Here you can read what it is and when you can expect troubles if using boolean operations between compounds:

https://www.freecadweb.org/wiki/Part_MakeCompound

I have the feeling they are not usefull and could be replaced by fusions!

It depends on the use case. Sometimes you do want a compound and sometimes a fusion. A fusion between two solids takes more computation, can fail and the result is a solid. With compound you get a single object and there isn't anything special going on when creating it. Like for example trying to join two solids in new solid.

[chrisb]

Hello
Can somebody tell me or point me the documentation page if available that explain what compounds are used for, what functional difference with cuts and what gain is expected.

A compound is a collection of objects tha tcan be moved together. If they don't intersect it behaves almost like a Union.

The problem is that compounds do not work completely.
Here are some cases they do not work:
- Fusion of two compound (In my test leads to black objects)
- Cuts of two compound (result unpredictable)

If you want boolean operations it is best to take boolean operations. Usually this means to make a Fusion instead of a compound. Compounds leave the objects as they are, you can see it at the missing seams. They seem to be faster than fusions.

[plgarcia]

Ok I see.
This has been invented for performance reasons for parts not intersecting but no control is made to verify if this condition is met.

Thanks for this information.

[triplus]

This has been invented for performance reasons for parts not intersecting but no control is made to verify if this condition is met.

Not exactly. As explained compound and fusion are basically totally different things. Geometry in a compound can intersect. If using such compound after in boolean operations (containing geometry that intersects). You can expect issues.

One use case for a compound is/was to for example add drawing views in Drawing workbench. As you could only select one object (TechDraw improved this area).

[plgarcia]

Thank you. I think I clearly understand now!

[microelly2]

Compounds are used for the animation of groups of objects. It's like an assembly. You can rotate some gears and move the whole engine as a Compound.

[triplus]

Thank you. I think I clearly understand now!

You're welcome.

[Cekuhnen]

Fast forward 2021
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Can compounds also be used in part WB to create a single object ID similar to a part?
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Further :
When using multiple objects with Boolean commands the nesting can be very hard to navigate and show hide only the state of a feature set the results into a final body.
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Screen Shot 2021-07-27 at 8.49.45 PM.png (29.35 KiB) Viewed 2484 times

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When using the build in part command the design tree gets very dense:
I assume this is because of how it is nested?

Screen Shot 2021-07-27 at 9.34.29 PM.png (110.61 KiB) Viewed 2449 times

[chrisb]

Every object has a unique name, which can differ from the label shown in the tree. As far as I know, realthunder has beyond that introduced a special ID in connection with the toponaming. He has also done special things concerning visibility.

We had asked you, not to open for everything a new topic. I am pleased to see, that you follow the advice, but this wasn't meant to search and necrobump very old topics, possibly even based on previous stable versions. It is then better to create a new topic and link the old one. The hint was rather meant concerning your own topics with the same model recurring.