Uh… maybe I’m using terms incorrectly. I just refer to any complete drawing of something as a model. My bad if that’s wrong.
No that’s not it. We need something to work with, not some screenshots or a video in about a month. Aren’t you interested in knowing what SketchUp is doing incorrectly (here), if at all. I know I am. Without the model (the file with that object as …skp) no one will know so we can’t solve your mystery and/ or file a bug report.
I have this happen from time to time, particularly when intersecting complex surfaces, and especially with unclosed shapes. Then there often is no “in” or “out” and it’s easy for SU to get confused. Another good reason to model exclusively in monochrome with back faces set to a wild color.
3 Likes
If you (a long time ago) read another OP thread about this tank you would know that uploading a file is a big challenge, The cannon itself is 5 Gb as I remember (though I don’t know how that’s possible, but that’s what the author said)
The cannon itself is 5 Gb as I remember (though I don’t know how that’s possible, but that’s what the author said)
Heh, yeah, about that. I was exaggerating a little. Actually, a lot. 
The complete vehicle model weighs in at around 100 MB. That includes turret and hull exterior and interior, along with the running gear and, yes, the main gun.
1 Like
I thought so
So WeTransfer or Google Drive should be no problem to share your model…
As said many times before that’s the only way to get to the bottom of this…
1 Like
It added to the draaaaaamaaaaa. 
It’s in no way a big deal. Even the renders don’t seem to have been impacted by reversed faces. If they were/are I’ve not even noticed.
Most renderers ignore back sides of faces. So if you are seeing no effect from reversed faces you made a fortunate choice of renderer.
Do you mean they don’t see it/won’t render it, or that they ignore the fact the face is reversed and render it as normal?
I’m using V-Ray, and so far as I can tell have never had a face not render (properly) if it was reversed, or even for any reason. It seems to be a pretty forgiving renderer, actually. If there’s a mistake you can make I’ve made it, since the sum total of my previous 3D experience was zero, and yet so far it’s been pretty painless.
Five stars, two thumbs up, would recommend to friends.
I mean that they don’t render the back side of a face. They assume that back sides are intended to be the interior of opaque solids, hence can be skipped to avoid wasted rendering effort on things that are obscured anyway.
Hmmm. I’m certain I’ve never seen reversed face issues arising within my V-Ray renders. Maybe it defaults to treating reversed faces as normal ones?
Reversed faces in renders are one thing, and very annoying they can be, but it is a fundamental of how sketchup understands geometry.
If you get it wrong it can wreck havoc.
Here is a simple example.
Two cubes with an internal cube, cut at an angle with a section for visual reference. The geometry is identical, the only difference is the face orientation.
Can you tell me which one will 3d print as a cube with a cubic void within it or two solid cubes, effectively just printing one solid cube?
It is a hugely significant difference that is controlled by something as simple as face orientation.
4 Likes
It’s just weird how faces can spontaneously flip.
Because edges share vertices, faces share edges, etc., SketchUp constantly rethinks its database to try to make sure it has shared everything in the best way. Sometimes the analysis can’t figure out a perfect answer but may have flipped faces while trying.
2 Likes
Help! Sorry to bother- dunno if this will even reach you. Generally the SketchUp forum is awful to navigate for a Mac user, but I found one of your Mac friendly responses on another thread and I was wondering if you know how to edit the default material (like to make the back green or vibrant) on MacOS? When I go to users>library>application support the only thing I can find for SketchUp (for any year I have) is an extension folder without anything for materials. Do you per chance know where I might be going wrong? Or have any suggestions for how to find answers about macOS questions with less difficulty here?
Do you mean this?
The default material colors for back and front faces are choices found in the style panel. Choose edit and scroll through the pages with options for all kinds of display settings via the icons across the top. Once you have it set up as you like, update the style by pressing the upper left icon with the circular arrows. Then do as many do and save that as your new default template so it is your personal starting style every time. Sorry I’m on my phone or I would show a pic, no doubt someone else will come along to show what I’m talking about if you have trouble. This is the same for mac and pc
1 Like
… is it ? many of us are on macs here though. and the forums navigates the same on mac or pc, it’s more of a browser thing isn’t it ?
Careful. Let me use an analogy. You’re trying to turn on your fog lights. and instead of tinkering with the levers and buttons inside your car, you’re currently elbow deep in your motor compartment.
Going to the library is useful to fix errors, reset broken stuff, and at times, transfer elements from one version to another.
Be even more careful (carefuller?), you’re using a beta version of mac os, Sonora is not released yet, and Sketchup 23 is not supporting Sonora. you might have bugs and crashes, and it’s normal. And you tinkering with the library files might actually be a risk since we don’t know how Sonora and Sketchup will react with that.
Endlessfix gave you the solution, it’s in the style panel, under the “edit” button, you can edit the front and back.
https://help.sketchup.com/en/sketchup/choosing-style
The look of the window panel and the mac one are a bit different, but buttons and choices are in the same spot.
Start a new thread. You have a question about - let’s say - colour panel ? Start a new thread in the Pro section. You can also use the search tool, top right of the forum, to see is anyone has got the same issue and got a solution yet.
Many, many of us here are on mac, or both, including a good chunk of the sketchup team. Being on mac is a non issue here. 
2 Likes