How to have a boundary box around a whole group instance?

Question

Enabling bounds display on a group instance draws bounding boxes for each individual object:

How to have a boundary box around the entire group instance? Via python or not. It seems to possible, this guy did it: https://vimeo.com/139789313

Answer 1

I wrote a small addon for another question that creates a bounding box around all selected objects. It seems it needed a little update to work in current versions of blender which is now available.

This does not create a dynamic bounding box, it will only match the objects you have selected at the time you create it, this can just be deleted and re-created whenever you needs updating.

After selecting one object you can use ⇧ ShiftG->Group to select all objects of the same group before creating the bounding box.

Answer 2

From a python perspective, Ill give you a pseudo run down of how I might approach this:

1. copy the group.
2. join each object in the new group together as one object.
3. get the bounding box of the new joined geometry object.
4. delete the new object.

Answer 3

Well not sure about python as my coding skills are next to zero, but you could do this manually for each different group in the following way:

1. Add a new default cube mesh to your scene
2. Enter edit mode
3. Select all with A
4. Press X to delete and chose Only Faces option. (That should leave you with a wireframe-like edges only skeleton of the cube.)
5. In the Properties Window > Object Tab> Duplication > Choose whichever group you want to duplicate
6. Now (still in edit mode) manually adjust the size of the cube edges to bound the duplicated group

Now you have a manually created bounding box., you can even customize the shape of your wire-frame mesh to suit your liking and have a custom bounding box shape, since it has no visible geometry it should not affect your rendered images You can even use it as a custom dummy object for snapping or helping place the group where desired.