A question came up at Bryce Camp 2000 about boolean modelling. It went something like this:

I group a positive cube and a smaller negative cube to carve out a room, and that works, but then I make another negative cube and group it to make a window and that doesn't work! Why not?

There were three answers to this, all of which will work, but the first two have some minor flaws.

The first answer was:

When groups are created, they are boolean neutral by default. In order to have the window cut itself out of the room group, you must first make the room group positive.

That will work, but it will create two levels of grouping and needlessly complicates the scene.

The second answer was:

All you have to do is ungroup the first group, select all the bits and then regroup.

That also works, but it will cause Bryce to forget the name of the original group. For the situation as described with three cubes, that's no big deal, but if you've got a very complex scene going, losing a group name can be somewhat of a pain.

Here's my answer, and I've found that it makes working with boolean groups much easier and faster:

Duplicating an object that is a member of a group will also be a member of that group and will participate in the boolean operations.

Make the first simple group of the positive cube and negative smaller cube to create the room, name it " room group." Then, hold down the control key while clicking in the wireframe to get the selection pop-up menu. Select only the negative inside-of-room cube. Duplicate it using the keyboard shortcut command-D (or control-D on windows). Do not use copy-paste, because the pasted object will not be a member of the group. Now all that needs to be done is to resize and reposition the duplicate to cut out the window. Oh, and you might want to rename the duplicate, too.

That's it - no ungrouping and regrouping, no need for multiple levels of grouping.

Also, you can duplicate a member of the group, then use the double-ended arrow in the Edit palette to change the duplicated object to any other primitive and it will still be a member of the original group and behave in the boolean operations accordingly.

 

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