Help! Invisible faces!

[Thecla]

I'm a Blender newbie, for starters, and am wading in deeper by the day with respect to uploading mesh and seeing what works and what does not. Today I've encountered something I can't figure out; an ashtray with some invisible faces along some boolean cuts. I did check "hole tolerant" during the operations, and went back and made quads out of the resulting geometry where it cut through a bevel. I've gone back looking for doubles and other potential trouble makers but I can't find a cause. I've also checked the normals on the faces. Any other suggestions about what might be going on and how to fix it would be most appreciated.

Blender:

https://i.imgur.com/22Zn4c2.png

SL Mesh:

https://i.imgur.com/A9G5bcd.png

[arton Rotaru]

I know you said you checked normals, but this looks pretty much like flipped normals on those faces. I would enable backface culling, and hit Shift+N to recalulate outside.

There seem to be an awful lot of Ngons on that mesh as well. I would recommend to get rid of any Ngon before exporting that mesh.

Edited April 3, 2023 by arton Rotaru

[Aquila Kytori]

The screenshots you linked to appear to show two different versions of the ashtray? :

 

[Thecla]

Wow, I learned a lot in 24 hours, lol. First of all Aquila, yes I had gone back and redid the boolean, with a simpler shape, and the problem persisted and I did not bother taking a new snapshot. Apologies for the confusion.

I had gotten away with ngons previously on some things I had uploaded and so was sloppy. They are now banished, and starting to learn how to alter/fix the topology to avoid or get rid of them has been a useful education.

Lastly I've learned some things about boolean operations and how messy the resulting topology can be, and a few beginning techniques to get the right result. For example I had lined up the positioning of the cutting piece so an edge traversed a facet, thinking in my monkey brain that of course Blender would consider me very helpful. Not in the least, it resulted in hidden vertices and all sort of messy business.

All that said, I'm still having the same problem. Here is the new mesh, and the upload preview. Arton, I tried to enable backface culling and did a shift-n, but not sure I enable backface culling in the right place, and shift-n did not give me confirmation that anything had happened.

Blender model

Firestorm preview

Addendum:  Just deleted and rebuilt the missing faces and now they are showing up.

Edited April 4, 2023 by Thecla

[arton Rotaru]

I'm afraid I don't know either where the right place is to enable backface culling in Blender. The last Blender version I have used was 2.39b. I only remember that Shift+N did recalculate the normals. I also remember that Blender was very poor in determining which direction a face should be.

Personally I try to avoid boolean operations as much as I can. However, sometimes it's the easy way out. And fixing up the messy topology afterwards might be simpler than modeling the shape. Most of the times it's not, though.

[Aquila Kytori]

For arton, just in case you ever want to get back to Blender one day 

Backface Culling is now enabled in the Viewport Shading drop-down :

 

Blender also has a useful option which makes finding incorrectly orientated faces easier. When enabled, faces with their normals facing outwards are coloured blue and faces with their normals facing inwards are coloured red. ( Just as Thecla was illustrating in the very first screenshot of this thread). This Face Orientation option can be found in the Viewport Overlays drop-down :

[arton Rotaru]

6 hours ago, Aquila Kytori said:

For arton, just in case you ever want to get back to Blender one day 

That might indeed be the case one day. I only hope that Blenders UI hasn't changed again until then.

Thank you!