Boolean Modifier issue


I have a vehicle I am re-meshing in order to create all quads. I re-meshed the entire hull already and now must add attachments onto it. In the example below, I am attempting to add multiple view ports to the hull assembly. In order to join the two objects together so that I can begin to recreate the topology, I am using the boolean modifier. Below is a picture of the hull assembly as well as the viewports.

Hull assembly:

Viewports to be added to hull:

When selecting the hull and applying a union boolean modifier, this is the result:

If I select the intersection, the result is the opposite of this.

Of course, neither are correct as I want to keep everything but the intersection so that I can remesh them together.
I also tried Make Normals Consistent on both objects with no improvement.

How can I fix this so that they can be joined together without having other parts of the model disappear?

I think the one you want is Union. That’s the one that will keep both.

Well, he tried union, but that failed obviously (see text line directly above the second image).

However, I think I see various normals issues on your mesh. A face (polygon) has by definition only one side, a front side, but no back. The “face normal” defines which side is the front - think of it as a vector protruding from the front side. In Blender this is visualized with the backside having a slightly darker shade of grey than the front side. In general all normals should point to the outside of the mesh.

What seems to happen in your case is that the normals of the view ports are flipped (pointing inward) and the normals of the tank are inconsistent (some pointing inward, some outward) - the tank literally turns inside out in some areas and back again. Blender doesn’t understand how to deal with that.

Try recalculating the normals of both meshes by hitting Tab to enter Edit mode, A to select all, W > Remove Doubles and then Ctrl-N.

This is just a guess - without seeing the file.

You’re right… I missed that he said he tried Union. I just did a quick test, and your guess is right. Fix the normals on the hull, and it should work.

In my previous post I mentioned that I had tried recalulating normals. (I also removed doubles which I didn’t mention). I will attach the file because I have no idea other then those two reasons why this would occur.

See attached. M113_Blender_hull_viewports_addition.blend (1.49 MB)

The viewports aren’t solid: their undersides have no geometry. This confuses the boolean, as it can’t calculate what’s “inside” and what’s “outside”.

Also, the upper viewport doesn’t get merged because it doesn’t touch the main hull geometry. Once added, I’d extrude the viewport undersides a bit to make sure the geometries intersect.

Has this mesh been imported?
It has a whole lot of wonky custom vertex normals which cause the weird shading artefacts that looked like face normals issues to me. Delete those custom normals as described here (this will not sort your Boolean issue, but solve the shading problems).

Indeed, Booleans are mostly about the interaction of solid objects, not of surfaces.

That’s the Rhino from Warhammer right?

You’re already using too much geometry.

Looks more like a M113 to me…

Yeah,i see now.

Looks similar to the rhino but it has that sensor thing on the hatch.

Yes, this is the M113. This isn’t for gaming or anything.