Correcting reversed faces

Correcting reversed faces can be a pain. Luckily, there are plugins to help you deal with them quickly, such as TIG’s Fix Reversed Face Materials plugin. TIG points out that if you are drafting properly, you shouldn’t have reversed faces in the first place. I have been trying to find out how SU determines whether a face is outer or inner to try to correct bad practice. It seems pretty haphazard to me at the moment. Can anyone point me to an article that explains it?

I don’t know of an article that explains it. There are things you can do to prevent them. A common situation that results in reversed faces comes when drawing a floor plan on a face drawn on the ground plane.

The reversed faces aren’t desirable in this case but the result shouldn’t be a surprise. SketchUp is doing exactly what it should. Look at it from the opposite side.

There are some other cases where reversed faces should be expected such as when using Intersect Faces to create a hole in which the “cutter” has normally oriented faces.

Sometimes Follow Me operations result in reversed faces and that one seems to be a little harder to pin down.

In any case where you get reversed faces, fixing them right away is the best and easiest way to work. Keep your model clean as you go and you’ll find the whole modeling process easier.

Good advice. However, the problem sometimes occurs with models imported or with legacy drawings. I did come across something that rather cleverly identifies all reverse faces in a model and then allows you to correct in one go. But it’s quite expensive as a plugin and it’s not form one of the trusted resource centres, so I am not tempted to invest. You can see it here:

No article known although there must be one or more.
Creating a face adjacent to an existing face may trigger SketchUp to use the same face_normal, giving you corresponding oriented faces, especially with the ‘Rectangle’ tool.
Tip: have a shortcut key set up for ‘Reverse Face’ and when hovering with some tool like ‘Follow Me’ over faces they’ll select. At that time press the shorcut key. It’s quite fast.

If you download Didier Bur’s Automatic Face Reverser, it includes a document that I think tries to explain how SU determines a face orientation. Not sure I followed it, but it seems to be there! See here:

Yes. I find it especially annoying with components from the 3D Warehouse. It’s one of the reasons I almost never use components from there. It’s easier and faster for me to draw them properly from scratch myself than to repair someone else’s garbage.

I guess if you need the capabilities it could be worth it. If you have to fix a bunch of your own older drawings, you could find it worth it. How much is your time worth? Or maybe it makes sense to redraw your old models instead of trying to repair them. You probably have a better, more efficient workflow now.

That’s an excellent tip!

Don’t know if it’s a Mac thing, but I cannot find Reverse Face in the list for creating shortcuts. It is in the right click options built into normal operations, though.

If a shortcut is a context menu option, you need to have the relevant action active to be able to set the shortcut.
In other words, select a face and then go looking for the shortcut.

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You may have to have a face selecte prior to looking into the list of available shortcuts. The list expands upon certain selections when wanting to create a new shortcut key. It’s sort of context sensitive, the list shown.
it only looks like I copied Box’s answer :smile: but didn’t

I attach a screen print of what I see in Preferences/Shortcuts. No Reverse Faces, even with a face selected.

Looks like you also have the edges of the face selected. Select only the face and try it.

Thanks @DaveR, that did it!

… there is also the r-click option to orient faces - use it on a “correct” face and the rest should flip to match the one you selected.

Indeed. I hadn’t used that before but it certainly speeds things up.