Boolean Tool Problem

[tdavis2000]

Hi All,
I'm trying to combine objects and retain their materials so I'm using the boolean tool. But I'm encountering a constant problem where the objects disappear upon application of the tool. It works fine with simple objects, but happens often with custom complex objects. Sometimes I'm able to fix it by moving the pieces but I'd like to understand the root of the problem.
I've attached a project with before and after folders of the objects. You'll see the "after" has the resulting combination object, but it is invisible.

Thanks in advance for any insight.

Terry

 

[frank beckmann]

Seems the "hood" is already a "bad" result of Boolean activity, when you look at the inside/backside of the mesh. And the result is not invisible but is empty.
Is there a valid reason to use Boolean add over "Merge" which works flawlessly?
Edith: Attached file isn´t meant as a correction by no means - just a proof of concept.

 

[Helmut]

* As says Frank:
* Why apply a Boolean transformation to the objects of this model? There is no real need for an additive Boolean operation.
1 A merge would suffice
2 Even a simple hierachy (hood > strap + symmetry / buckle+ symmetry) will do.

* If I were to model a similar compound object:
*

* Note that all (-1) objects are parametric and can be modified if needed.

 

[Helmut]

* Maybe a bit advanced, but possibly useful for future models:
* There is a script, Spline Wrap.js, by Hiroto, which may be useful.
* It allows you to flow on a 3D mesh onto the axis of a spline (shown as a red curve), be it a simple 2D arc, a helix or whatever.
* The script does have some limitations, but it works fine with modifiers added.

 

[tdavis2000]

Ahh, I see. I was unaware of the merge tool- and that solves it.

But if you have time, it would be great to understand how one gets a "bad" boolean result, and what that means.

Helmut, I appreciate the parametric insight. (I needed it all as a single object because I was going to animate it with bones.)

Thanks so much for your help!