Booleans and avoiding headaches

[hairyspin 1]

I threatened to post more on Booleans recently, so here goes... I’m making this a separate post so it can be found easily. Boolean operations can cause all sorts of grief when things are anything more than simple, so here are some methods for getting out of trouble.

 

This is just a rehash of tips by Mathias over at SOH: he’s a real Jedi Knight of modelling, I just hope to make Apprentice grade some day…

 

Simple Booleans might be like cutting the elevator out of the tail feathers:-

 

 

 

 

 

which leaves you with the elevator polys ready to Detach as an elevator object:-

 

 

 

 

 

A more complex cut might be cutting a tail feather into the fuselage:-

 

 

 

 

and you might think this would be simple, but in fact this one won’t work! The reason is the mesh isn’t closed. Hiding the fuselage and looking at the stabiliser from the other end shows why:-

 

 

 

 

The end that is to be cut into the fuselage is open – so create a poly to close it, like this:-

 

 

 

Now you can try the Boolean cut, and this time it succeeds (I’ve hidden the stabiliser):-

 

 

 

 

But this is still relatively simple, so here’s what happens in a real-life case. This is the cockpit of my current warbird project and I’m trying to cut the left-hand instrument panel, Box03, to fit neatly inside. I could cut it to just stick through the cockpit inner wall, but that would give mapping problems later, plus the overlapping poly problem would be impossible to hide in the VC.

 

 

 

Hiding all but the cockpit interior shell and the left-hand panel makes the problem easier to understand:-

 

 

 

A Boolean op here will cut two vertices on the panel and nothing else. Closing over the cockpit opening is likewise no help at all, the mesh is just too complex for gmax. We have to simplify the mesh to make the cut.

 

 

First, clone the cockpit interior shell and hide the original. I’ve named the clone shell01. Select all polys in Left View and make two slices, one each side of the panel:-

 

 

 

Since we're cloning the interior, with inward-facing polys, convert to Editable Mesh and Flip all the shell01 polys to make it easier to see what we're doing.Then delete all the polys except those immediately around the panel:-

 

 

 

This gives a much simpler mesh for gmax to deal with, but still accurate to the VC. Now we have to close the mesh.

 

In this case I have a poly at the bottom which can be usefully stretched by moving vertices. Without that I would select the bottom edge of shell01 in Editable Mesh and Shift+Move it to extrude a poly:-

 

 

 

The bottom poly is extended beyond the panel. The top poly has a bent edge so, in Editable Poly, select both these polys and slice them straight:-

 

 

 

Delete the two excess polys created by this slice. Now we can create a poly to close the end:-

 

 

 

Now close the two remaining open ends. If you wondered what use the poly sub-object Border is, here’s one. Select each border in turn and Cap them:-

 

 

 

like this:-

 

 

 

Go round to the other side, select the open border there and Cap that too:-

 

 

 

We now have a greatly simplified, closed object to cut the panel with, so full ahead with the Boolean:-

 

 

 

Box03 (the left-hand panel) is cut with shell01 (the simplified mesh) and a dialogue box asks if we want to inherit material from shell01 – this means the panel will adopt the colour of shell01 (amongst other things). No thank you, I’ll make material decisions later:-

 

 

 

Finally we can hide shell01 (or delete it) to show a successful operation:-

 

 

 

Select and delete the unwanted polys, close any edge gaps as required and the panel is ready to fit perfectly into the VC.

 

 

It may have occurred to you that I am recommending the Reference Boolean, Cut and Refine in all cases whereas there are more options. This is deliberate, because it leaves all of the cut object visible and the modeller can see whether the operation has been a success before deleting unwanted polys. As you gain confidence, you can try the other options.

 

And just to prove that nobody knows it all, BH has just posted another way around boolean problems:- http://forum.combata...ai-top-decking/

[ConradB 0]

Thanks for posting that! I have saved it to my folder on bits and pieces.

[Bullethead 12]

Hey, that's a neat trick. Thanks!