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History Bug ? (#728)
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jol  
#1 Posted : Monday, December 10, 2007 5:18:21 AM(UTC)
jol

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- union 2 objects

- move or flip them to a new location

- remove the union feature from the feature tree

One object is annoyingly returned to it's starting location

Why ?
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jol  
#2 Posted : Tuesday, December 11, 2007 8:05:42 AM(UTC)
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Isn't this a pretty fundamental flaw in using the feature tree ?
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billbedford  
#3 Posted : Wednesday, December 12, 2007 3:12:30 AM(UTC)
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jol wrote:
Isn't this a pretty fundamental flaw in using the feature tree ?



It's not something that I would do every day.
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jol  
#4 Posted : Wednesday, December 12, 2007 3:58:54 AM(UTC)
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Bill, I do .. at least every few days .. and I wonder why my model falls apart

We can't have the removal of certain features shooting your part up the history tree .. especially when these parts may have multiple dependencies

It's a bug and it needs fixing - so next time I remove a feature, my model won't fall apart

I don't much care if removing features is not something you do Bill
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billbedford  
#5 Posted : Wednesday, December 12, 2007 5:43:42 AM(UTC)
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jol wrote:
Bill, I do .. at least every few days .. and I wonder why my model falls apart

We can't have the removal of certain features shooting your part up the history tree .. especially when these parts may have multiple dependencies

It's a bug and it needs fixing - so next time I remove a feature, my model won't fall apart

I don't much care if removing features is not something you do Bill


Union is the permanent joining of two objects to make one new one. It is *not* designed as way of temporally joining to objects so that they can be moved in association. The history tree tells you that. If all objects in a union were going to revert to their pre-union position if the union was to be removed then any translations that were done on the unioned object would be copied to each branch of the tree after the union.

If you want to translate objects in association use 'Group'.
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jol  
#6 Posted : Wednesday, December 12, 2007 6:59:33 AM(UTC)
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eh ?

Thank you Bill ..

you're talking rubbish though

Where in Concepts is a Union defined as a "permanent joining of 2 objects"

In the manual it says "The union boolean (also called add) operation is used to combine two shapes into one."

If it were permanent, then a 'remove feature' would not be allowed, would it ? And it is

.. SolidWorks does not allow you to remove a boolean as I understand

I would be very happy if Concepts forbid this too .. if it avoided this issue
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Tim Olson  
#7 Posted : Wednesday, December 12, 2007 12:17:47 PM(UTC)
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Jol,

I believe this behavour is correct. The xform step was a history operation based on a particular node. It does not impact prior nodes or operations. When you remove the boolean, the xform is still there and drops back onto the first block selected for union. The first item selected for a boolean is the object the preserves the tree branching. You will need to remove the Translate operation to get to the previous un translated position.


>>One object is annoyingly returned to it's starting location

It was never moved. The result of the union was moved.
Tim Olson
IMSI Design/Encore
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API  
#8 Posted : Wednesday, December 12, 2007 7:33:11 PM(UTC)
API

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Tim,
Can you post somewhere a concise set of rules for the History Tree. I don't think that its understood very well. What it means to be the first object picked.
Sometimes I duplicate a part with history. Move the new object to a new layer. If I "remove feature boolean", I get a dialog that the object will go to the parent layer. When I'm all done, I usually can't find it.
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jol  
#9 Posted : Thursday, December 13, 2007 4:31:37 AM(UTC)
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Tim, that's a classic Captain Spock answer .. we're carbon units .. and what's more, we're designers !

I see what you're saying .. and in your/ACIS logic, perhaps it's right.

However, with some of this stuff, you need to think what the designer is doing .. and think what the designer is thinking

If the designer moved an object from A to B, then changed it's colour from green to purple .. if he undoes the move back to A .. does the colour of his object change back from purple to green ? No !

The designer has asked that this union is undone .. he has NOT asked that the translate is undone for one of the partner entities only (.. or that any other feature change inbetween is undone). You cannot assume this .. however 'logical' it is

If the intent is in doubt, a dialog should make it quite clear what these 2 options are :

- just undo what I'm asking you to undo
- undo what I'm asking you to undo .. and incur the knock-on effects in ACIS logic
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jlm  
#10 Posted : Saturday, December 29, 2007 3:08:06 PM(UTC)
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I just spoiled a big project with that :
disassembling complex screw parts that had been moved of a small amount, I got all the threads off centered on the final model...

A feature that can silently spoil your work is worse than a bug !
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