Part compound vs. Std Part

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Roy_043
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Joined: Thu Dec 27, 2018 12:28 pm

Part compound vs. Std Part

Post by Roy_043 » Fri Jan 17, 2020 3:17 pm

I am wondering if Part Compound has become obsolete with the introduction of Std Part. What are the typical use cases of a Part Compound?
openBrain
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Re: Part compound vs. Std Part

Post by openBrain » Fri Jan 17, 2020 3:25 pm

Actually a Compound is a base type. Eg. all boolean operations of Part WB lead to a Compound (IIRC).
Also a Boolean Fragments (for example) leads to a Compound on which you can eg. apply a Compound Filter.
This isn't possible with a Part container.
Also Compound doesn't create a LCS but lives in the current system. ;)
vocx
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Re: Part compound vs. Std Part

Post by vocx » Fri Jan 17, 2020 4:04 pm

Roy_043 wrote:
Fri Jan 17, 2020 3:17 pm
I am wondering if Part Compound has become obsolete with the introduction of Std Part. What are the typical use cases of a Part Compound?
As far as I can tell, a compound (Part_MakeCompound) is a basic object defined by underlying OCCT classes, so it's kind of like a boolean operation, which groups various objects but without fusing them.

Compounds are used internally by scripted objects to group various Shapes into a single object. For example, Draft_Arrays are compounds of copies of a base object; in the tree view the array appears as a single object.

If you are talking about the field of mechanical assembly, then yes, Std_Parts have basically supplanted compounds. But the basic Part compound (a collection of shapes) is still used internally by different tools in all workbenches.
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Roy_043
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Re: Part compound vs. Std Part

Post by Roy_043 » Fri Jan 17, 2020 9:29 pm

Thanks for your answers.
openBrain wrote:
Fri Jan 17, 2020 3:25 pm
Also Compound doesn't create a LCS but lives in the current system.
Is this really the case? In terms of LCS (Local Coordinate System) a compound does seem similar to a Std Part. At least it does not behave as an Arch BuildingPart. But maybe I have misunderstood.

EDIT: Typo.
Last edited by Roy_043 on Sat Jan 18, 2020 9:18 am, edited 1 time in total.
chrisb
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Re: Part compound vs. Std Part

Post by chrisb » Fri Jan 17, 2020 10:35 pm

A compound has indeed its local coordinate system, as it has its own placement, which is in (0,0,0) after creation. But compound does not expose it any further by means of an Origin, like StdPart does.
openBrain
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Re: Part compound vs. Std Part

Post by openBrain » Sat Jan 18, 2020 12:38 am

chrisb wrote:
Fri Jan 17, 2020 10:35 pm
A compound has indeed its local coordinate system, as it has its own placement, which is in (0,0,0) after creation. But compound does not expose it any further by means of an Origin, like StdPart does.
I would say a Compound doesn't have an LCS. It has a placement inside the current one. ;)
Roy_043
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Re: Part compound vs. Std Part

Post by Roy_043 » Sat Jan 18, 2020 9:32 am

As I understand it the placement of an unnested compound is expressed in the GCS. The objects nested in the compound use the compound's LCS.
openBrain
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Re: Part compound vs. Std Part

Post by openBrain » Sat Jan 18, 2020 11:50 am

I have no computer now to test, but one can easily try.

Compound together a Part/Sphere and a Part/Cube, then move the Compound and check if the primitive items moved together with the Compound or stay at their original locations. ;)
chrisb
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Re: Part compound vs. Std Part

Post by chrisb » Sat Jan 18, 2020 12:32 pm

They move, even the Transform tool is available and works.
openBrain
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Re: Part compound vs. Std Part

Post by openBrain » Sat Jan 18, 2020 12:45 pm

chrisb wrote:
Sat Jan 18, 2020 12:32 pm
They move, even the Transform tool is available and works.
Thx for testing. ;) This is interesting. Does the primitive objects stay @(0,0,0) or do their placements follow the one of the Compound?
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