Face filling frustration!

Hi again everyone,

Having more noob difficulty here…

I have been tinkering with this dumb blockout for HOURS, and I can’t get all the roofs to fill in at the same time. I’m finally down to the last one, but it refuses to fill, and I can’t understand why. Sorry the model looks messy, here’s what I’ve done to troubleshoot so far–after many hours of having the exact same issues with other parts of the model, and then suddenly they form faces, but it’s not clear what was wrong:

  1. Set angle guides for the roof on every wall corner, and verify that they’re identical.
  2. Measure every linear dimension of every room, and ensure all corners are square.
  3. Draw lines over angle guides to facilitate accurate snapping.
  4. Draw diagonal lines from corner to corner of open faces; sometimes a triangle will form, but only in one direction; sometimes it won’t.
  5. Check and recheck and recheck AGAIN that rooflines which filled are at the exact same angle as those that refuse to fill, and that all borders of open faces are symmetrical.

This is extremely frustrating, because I can’t imagine what I might be doing wrong on such a simple geometric structure; and when it suddenly works, I don’t know why it worked either.

Thanks to all of you for your generally prompt and detailed feedback! [Assuming anyone wishes to liberate me from my private purgatory. I’m going kookoo bananas here. I’ve tried everything I could think of several times before posting this.]

AMENDED to add this technique I just thought of…

I cleared the half-roof and filled in the flat plane atop the walls:

Then I drew a midline and moved it up to snap to the roof apex, which created a split face on the side that wouldn’t fill. But I can’t figure out why the perimeter is out of alignment; all measures look identical around the frame:

Why does SU consistently choose to flat-fill one side of the roof, but not the other?

That indicates that the edges outlining that roof are not in the same plane. SketchUp will not twist a face like you could twist a sheet of plywood or OSB if the trusses aren’t in a perfect plane.

You could avoid that issue and reduce the amount of work you are doing to create guides by using inferencing off of the first roof.

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Thank you for the suggestion, but I have been doing that over and over and over again, every which way I can think of, all day today, and it behaves unpredictably. Sometimes it fills the faces, sometimes it doesn’t. I use inferencing and shift-locking, but I also use many other techniques that also are not working.

@DaveR is right. That line that showed up in the side that was giving your trouble is your clue. It’s split into two faces when you pulled the ridge up from below:

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Yes, I know, but nothing else I tried before that worked either.

Have you tried simply starting over with that side extension and extruding the shape you want? Nice and clean that way.
Jul-17-2025 16-59-30

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Thank you, good idea, I’ll try that right now. But I would also like to figure out why it’s not working, so I know for the future.

That may be hard to determine. If you don’t know how it happened to begin with, there’s not a lot we can do to go back in time to verify.

OK, that extrude solved it! Thank you for taking the time to make the video. I guess from now on, I should just make every building unit a separate group, and then merge them if necessary [which I need to do for the roof-building plugin].

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Working with groups is a good idea. Remember you can always explode to merge after drafting or copy and paste in place inside of a group or component. When you have loose geometry sticking to loose geometry, if you’re not super careful, that’s how those little errors can pop up and cause headaches.

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I’ve become fluent at modeling in a way as to avoid the “chewing gum” of ungrouped geometry, but it sure would cause me less grief if I did groups even when I don’t need to. This face-filling ordeal has been an albatross around my neck. I don’t even feel like I learned anything, because I never figured out what was confusing SU about my geometry. Thank you for solving my problem!

A few tricks I use for finding inconsistent edges and faces:

  1. Under styles, change the Edge Style to “color by axis”
    This will highlight for you anything that is not “on axis”. You can also reposition your model Axis to match the angle of the roof, so it will highlight those as well. (then afterwards you will want to reset your model axis back to default)

  2. Add dimensions to some of the edges that you want to check. Adjust your Dimension settings so that it shows many decimal places.

  3. To detect any overlapping faces, paint all faces with a darkish colour and use X-ray mode, or make that colour slightly transparent. Then you can see where faces are ‘doubled up’ upon each other.

Also - when modelling angled roof areas, particularly if you are using Rotate or Copy Rotate, you may find that invisible (softened/hidden) edges area created by SketchUp. From time to time it’s a good idea to use “View > Hidden Geometry” to reveal them. You can use the Soften Edges slider and reduce it to 0. ( For some reason SketchUp defaults to having the Soften Edges slider part-way up, which can automatically hide some edges…I dont like this default behaviour).
The View/ Hidden Geometry is a very good tool set to a keyboard shortcut, then you can toggle it on and off as you model.

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Not sure if this was covered but one source of error creep is the Length Snapping setting. Try turning it off:

Also, you can hover the Tape Measure tool over vertices to show position. If the position has a tilde ( ~ ) it’s not exact which can be a clue that things have gone out of whack:

Or:

Thank you! Solid gold tips right there. One thing I knew about already was frequently checking for hidden geometry, but I didn’t think about the softened edges. I will make a wallet card out of your suggestions…

Thank you. I never have length snapping on. And I always look for that ~, which I did spot on one problematic line segment, but I couldn’t figure out why. I still don’t know why I was having all this trouble, but I think in the future grouping will make the process much easier. Also, the comment from AK_SAM just above has some good tips I didn’t know about, if you’re interested. Thank you for taking the time to make those screenshots for me!

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