Part compound vs. Std Part

[Roy_043]

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]

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]

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.

[Roy_043]

Thanks for your answers.

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.

[chrisb]

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]

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]

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]

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]

They move, even the Transform tool is available and works.

[openBrain]

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?