I’m very proficient with SketchUp, and I know when faces are reversed and when they aren’t. On this model, no faces are reversed. There’s no reason it should not be reported as solid. When Solid Inspector^2 thinks faces are reversed when they are not, and I click to fix it, it reverses the faces (wrong side out) and then says everything is shiny. See screen shots.
Before
During
After
Yes, it does that from time to time. Solid inspector isn’t infallible.
I wonder if viewing the model in Perspective instead of Parallel projection would make a difference? I am not a programmer, but I guess that camera position has a role in determining what is inside or outside.
True, but the plugin’s current iteration is so awesome that after my having used it literally thousands of times, I’ve not ever had anything this bad happen with it. Bit of history on how the model was made. The “insets” on the bin were carved using solid tools. That shaping was all done on only 1/4 of the bin, since the uniqueness all resides there and only there. The 1/4 component was then mirrored to make a half, and then those two mirrored to make a whole. After getting the above problem no matter how I tried, I also then also tried rotating a copy of the 1/2 component instead of mirroring. No joy. I tried exploding the whole bin component and regrouping. No joy. I tried making all the geometry firm instead of soft and smooth. I made sure all geometry is on the same tag (formerly known as layers). I even tried rotating the whole component 30 degrees, exploding, making it a group. Same 913 faces, get falsely perceived as reversed. 
If it reports as a solid in SolidInspector² and Entity Info then you should be able to fixed the wayward faces…
Edit the group/component.
Select a face that’s oriented as you’d expect and right-click > Orient…
All connected faces should rearrange to match that face’s orientation…
You’d think. See screen shots.
It does not report as a solid unless those 913 faces are left reversed. When I leave them reversed, then get “all shiny,” then right-click and orient faces, I get the following weirdness.
For “solids,” proper orientation is based on which side of the skin of the solid is facing outwards. It has nothing to do with camera angles. At least one plugin exists that allows switching orientation of all selected faces on any geometry (even those not solid or even close to it) to “face” an existing camera. But that has nothing to do with this. In a non-solid (i.e. the shape would not be an airtight container if existing in the real world) there is no right or wrong way to orient the faces because only solids have a proper “inside” and “outside.”
Any chance you could share the model? I have seen plenty of instances where SI gave a false report, but nothing of this size.
I just now solved it. The key was I happened to notice (see screen shot #5 in my prior post) that only after some wrangling after “orient faces” I got one report of an “internal face.” I located that, switched on “show hidden geometry,” cleaned up that area, then cycled the Solid Inspector plugin through several iterations of “fixing” “reversed faces” and I am finally at a solid that’s right.
I’ve noticed that both solid inspector and the orient faces can be confused by certain odd ways that faces meet. I can’t nail down exactly what does it (and I suspect that neither can the SketchUp developers else they would fix it).
I know. I was just thinking that @thomthom 's algorithm might be using some kind of projection method to determine what is “inside” and what out, and if camera location might have a role.
I hear you. I was grasping at straws until I found the culprit, a tiny polygon-ish area less than half a millimeter in size.
I made a post on my FB page about this not so long ago.
Fixit 101
A quick tip for anyone struggling to make complex solids.
When creating solids Thomthom’s Solid Inspector is a brilliant tool, but sometimes it doesn’t find and fix all the errors. It can leave you with a non solid and no real clue as to what the issue may be.
Anton S’ very handy Fixit101 can often find and fix the missing issues for you. Available from Sketchucation.
Cool tip! Thank you!!
It doesn’t. It works by traversing the surface and checking the normals. But there are edge-cases where the algorithm can be thrown off. If the model can be shared I could try to find what causes it in this model.
It was not the fault of your excellent plugin, but rather the model had a spot of bad geometry in it. It was tiny, and tough to locate. I gather that probably no plugin of this nature is infallible, but in this case it was my flawed model.
You can share the original model to help Thomthom to improve the behavior for those cases too…
The original model already had the flawed geometry fixed and the file saved, so I cannot provide the problematic version to Thomthom at this time.
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