Diff between "join" and boolean "union"?

 From:  Michael Gibson
1689.4 In reply to 1689.3 
Hi angeliclight,

> So, would you use join if you were modeling, say, a spaceship and
> you have the body, but want to put a lot of smallish details on the
> surface that look like small cubes, etc, glued on?

Well, it depends on how you specifically modeled those details.

If you created the small cubes as solids (like say by the Box command), then you would use booleans to merge them with the main hull.

It's only when you have individual surfaces that touch each other that you use Join.

So for example for a small cube shape - if you happened to build the cube shape by drawing 6 individual planes that touch each other, that's when you would use Join to glue them together into a single solid box.

It's somewhat more common to use booleans though, modeling things by doing one surface at a time (where you would then use Join) tends to be a more advanced type of workflow. It is easiest to start out by creating pieces as solids and use booleans to fuse them together.

> where you want lots of objects appearing to be "sitting on" or
> attached to the object underneath it, but not necessarily anything
> mathematically happening?

If your final result is going to be a rendering, and you don't need to do stuff like put a smooth fillet between the pieces, then you can often times just move pieces like that into position and leave them as separate objects and not actually do the work to make them in to one single object at all.

- Michael