Reversed Faces
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I've been using SketchUp for around 15 years as an architect, incorporating it into my daily work routine. Over the course of my career, I've rendered and 3D-printed hundreds of projects, but have always been frustrated by the issue of reversed faces, which can be soul-crushing to deal with. While I've tried numerous tools to fix this issue, I'm currently facing a project with thousands of faces that are not properly oriented. Unfortunately, fixing them all manually is not an option for me, as I need them to be perfectly oriented in order to 3D-print the object.
What I find puzzling is that SketchUp is able to depict these incorrectly oriented faces correctly as blue faces in its monochrome face style. However, neither SketchUp nor any other tool I've tried can seem to select and reverse them all effectively, often causing some of the correct faces to be changed as well. It's a real mess. Nonetheless, I'm curious as to why SketchUp is able to display these faces correctly despite the difficulty in selecting and reversing them. Perhaps some developers out there could shed some light on this issue and recommend the best tool to correctly orient faces. (I'm currently using SketchUp 2020-2022 on an Apple M1 Max with 64 GB RAM and macOS Ventura 13.2 (22D49)).
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CAD apps will struggle to orient faces 'correctly' if the source geometry is not tailored to be flipped.
There are many face orientation tools out there. If you go here https://sketchucation.com/pluginstore and search 'reverse' you'll see many.
Which one is the best? I tend to use a few because its normally a case where a tool helps with 70% then I switch to another to to tackle the stubborn 30%. Until I finally have the minimal amount of manual flipping to do.
Didier's and TIG's tools are my go to choices.
SketchUp Plugins | PluginStore | SketchUcation
SketchUp Plugin and Extension Store by SketchUcation provides free downloads of hundreds of SketchUp extensions and plugins
(sketchucation.com)
SketchUp Plugins | PluginStore | SketchUcation
SketchUp Plugin and Extension Store by SketchUcation provides free downloads of hundreds of SketchUp extensions and plugins
(sketchucation.com)
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What is the source of the geometry for your model? Perhaps the best thing would be to go back to the source and correct the issue there.
If modeling from scratch in SketchUp, it's best to learn techniques to avoid creating the reversed faces and fix them immediately when they do occur. I rarely see reversed faces as I'm modeling even in very complex models. I've set the back face color to something that is easily picked out and I reverse the faces immediately in the cases where they do appear.
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@dave r said:
What is the source of the geometry for your model? Perhaps the best thing would be to go back to the source and correct the issue there.
That's the issue: the buildings were sourced from public data files. I don't encounter any problems with incorrectly oriented faces when working with my own files.
However, what I find confusing is that even though SketchUp is able to identify these faces as blue faces, they are not selectable. I'm curious to know the reason behind this limitation.
Given that I've tried various plugins already, I can imagine that the developers must have also experienced similar frustrations when trying to program tools to select wrongly oriented faces. It seems illogical to me that none of the plugins are able to select them with 100% accuracy.
Currently, I'm dealing with models containing more than 250,000 faces, of which 10% are reversed. I have yet to find a satisfactory way to combine the available tools to achieve the desired result.
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@nikopol said:
However, what I find confusing is that even though SketchUp is able to identify these faces as blue faces, they are not selectable. I'm curious to know the reason behind this limitation.
It would be helpful if you could share the model file or at least part of it.
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This is a model I have already spent a lot of time on, manually reversing some of the faces. However, I still have 200 more to clean, so I need to find an automated solution to get this done.
http://www.kaestle.ch/files/H10_test.skp.zip
Thank you, and regards,
Roger -
I get a message indicating it can't be downloaderd securely.
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I was able to download the zip file, but had to tell Windoze to keep (via the dropdown indicator arrow) instead of canceling the download.
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You haven't explained why you want to reverse some of the faces.
Unless you want to 3d-print this the reversed faces are somewhat irrelevant.
The geometry is unlikely to ever be 'solid' of 3d-printing compatibility anyway - many buildings intersect the surface etc...
If you simply want to 'paint' materials onto some faces you can apply them to front or rear-faces, but if you want to use a render app the rear-faces will often not display as expected showing white/black etc...
In that case you need to do more editing and manually reverse incorrectly oriented faces. No software will be 100% fool-proof in automating that process... -
@tig said:
Unless you want to 3d-print this the reversed faces are somewhat irrelevant.
@nikopol said:
"I need them to be perfectly oriented in order to 3D-print the object."
That's the crux of the issue. While the STL file I receive is generally printable, any reversed faces do not print and instead generate unsightly artifacts. Unfortunately, none of the other programs I use to clean STL files, such as MeshLab, Netfabb, Meshmixer, Chitubox, or LycheeSlicer, are able to fix the reversed faces either.
Regards, Roger
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Maybe share a singular mesh with both correct and incorrect normals that fails to orient via SketchUp command or Extension.
Then we can troubleshoot. I'd be interested to see if these meshes report as solid too.
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@nikopol said:
It seems illogical to me that none of the plugins are able to select them with 100% accuracy.
By chance, did you try FredoTools::AutoReverseFaces, which is part of FredoTools (and free).
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