Simple (?) question about booleans

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 From:  Antlab
1390.1 
Hi all.
I am playing with the trial version of MoI (Michael, the new version is still valid after three days), and I have a question about booleans. The case is simple. I draw a rectangle, then extrude (a sort of "room"). Then I put a plane on one face, as a "door". Now, if I subtract the door from the room, I don't obtain a "hole". Instead, if I previously deleted the upper face of the room, the boolean operation with the door works as I expected. Maybe I am missing something fundamental about booleans operations in this situation?

Ciao

Antonino
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 From:  Michael Gibson
1390.2 In reply to 1390.1 
Hi Antonino - yes I see that is a bit odd.

The problem here is that if you have a solid base object, the booleans will tend to expect either a solid cutting object, or for a surface one that fully divides the solid into 2 smaller solids.

In a sense the booleans will try to generate a solid as the result if the original object was a solid.

If you want to cut out a piece of a solid like you are showing there, you should use the Edit/Trim tool for that type of cut instead. Trim does not attempt to keep solids as solids and will let you cut up the outside skin of a solid any way you want.

It may be easier for you to use Edit/Separate on the solid to break it into 6 individual surfaces first, and then work on those surfaces separately. You can then later on use Edit/Join to glue them back together into a connected object after you are done editing the pieces.

Also instead of using a plane as the cutting object, I'd recommend using a rectangle curve as the cutter instead. Coincident surfaces tends to be a more difficult calculation and also it can be more difficult to select by clicking when there are 2 coincident surfaces. Curves are much easier to select, so it is more of a recommended workflow to use a curve as the cutting object in this case.

- Michael
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 From:  Frenchy Pilou (PILOU)
1390.3 In reply to 1390.1 
???
No result is the same : roof or not roof :)
Select as on the image !
The door will made a hole :)

EDITED: 16 Feb 2008 by PILOU

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 From:  Antlab
1390.4 In reply to 1390.2 
Thanks Michael,

you are really superfast in answering :-)
I understood your explanations, and I will make some more experiments with the different methods. I am quite a novice in NURBS modelling, but now that I found a tool so nice to use as MoI, I plan to learn and improve my skills.

Ciao

Antonino
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 From:  Antlab
1390.5 In reply to 1390.3 
Hi Pilou,

Sincerely I did not understand your message (and the figure). I tried several times, so I am quite sure to have selected the room as base object and the door as object to subtract. Could you please explain better your results?

Ciao

Antonino
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 From:  Frenchy Pilou (PILOU)
1390.6 
in my example there no floor so that works :)

EDITED: 16 Feb 2008 by PILOU

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