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I have a very large and complex model that I'm working on, and I need to separate the external faces from the rest of the mesh for various reasons.

I decided to try making use of the Limit Selection to Visible feature to select all of the external faces, and then use the P command to separate the mesh.

Unfortunately, I'm having some trouble actually selecting all of the external faces this way. I had planned on dragging the Border Select over the entire object, then rotating through the appropriate angles and repeating until all of the faces were selected however, the selection tools aren't selecting all of the visible faces.

This is what happens when I'm zoomed out and I use the Border Select on a region of the model. Upon close inspection (zooming back in) I can see that there are a lot of faces that weren't selected. [See image directly below]

Selection while zoomed out

If I use the Border Select on the same region while zoomed in, it selects a lot more of the faces; though still not all of them. [See image directly below]

Selection while Zoomed in

It seems like the selection accuracy decreases, the further your view is from the model.

I need a way to select ALL of the visible faces. Is there a way to fix the selection accuracy, or a feature that I'm missing? Does anyone know of a script (or would be willing to make one) that is able to do this?

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    $\begingroup$ Try to select one of the front faces and select similar Shift+G>Normal and then you can extend selection with Ctrl and + $\endgroup$
    – Denis
    Commented Dec 17, 2016 at 21:28
  • $\begingroup$ If the outer shell is totally separate from the inner faces just hover one vertex of the outer part and press L to select all linked, or select one of it's vertices and press Ctrl+L to select all connected. $\endgroup$
    – Duarte Farrajota Ramos ♦
    Commented Dec 17, 2016 at 22:37
  • $\begingroup$ Denis and Duarte, thank you for your suggestions. The outer shell is in fact connected to the inner shell so unfortunately the Extend Selection (Ctrl + +) "bleeds" into the inner shell. $\endgroup$
    – Dennis
    Commented Dec 17, 2016 at 23:06
  • $\begingroup$ Mr Zak, thanks for your response. I cannot upload the full part, however I did slice a piece from the mesh that can serve as a good example of the overall part. As you'll find, the internal geometry is quite bad, which is one of the reasons that I want to separate the external faces from the rest of the mesh. Here is the example mesh: <img src="http://blend-exchange.giantcowfilms.com/embedImage.png?bid=2390" /> $\endgroup$
    – Dennis
    Commented Dec 18, 2016 at 0:25
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    $\begingroup$ Well yes, that's complex thing. The simplest way as of now is to enter Weight paint and paint weight of 1 on the outer part with Limit Selection checked. Weight Paint is not as bad at selecting as Edit mode. After that you might want to clear zero (or almost zero)-weights vertices, like here. Note that it won't make everything good - i.sstatic.net/CC3wG.jpg. Still I couldn't call the outer topology good as well.. $\endgroup$
    – Mr Zak
    Commented Dec 18, 2016 at 12:55

2 Answers 2

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  1. Select one of the front faces and hit Shift+G and from the menu select Normal.
  2. Hit F6 to bring Select Similar operator menu and adjust the Threshold until all the front faces are selected.
  3. Use Ctrl++ to extend the selection
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The simplest way to select only one part of that mesh would be to enter Weight paint and paint weight of 1 on, for example, outer part with Limit Selection To Visible checked:

screenshot-wight-painting-selection

After that you might want to correct some weights which came through the outer part to the inner part:

screenshot-fixing-weight-paint

Then clear zero (or almost zero)-weights vertices, left after the second step with Clean tool from the Toolshelf as outlined here - How to batch remove zero-weight vertices from vgroup?. Note that selecitng in this way won't make everything, because the resulting selection isn't really clean:

screenshot-final-selection

It might be a good start; you can eliminate some of the selected vertices by toggling Face selection mode.

As was said it is not a perfect solution, but I think it is the best way to accomplish this as of now. I appreciate the suggestions that everyone provided, and I believe I can put this question to rest for now. If anyone else comes up with an alternate solution at some point in the future, that would be great.

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  • $\begingroup$ Please incorporate some details in your answers here as that's how this site works so not jsut copy-pasting comment. Thanks. $\endgroup$
    – Mr Zak
    Commented Dec 19, 2016 at 15:40

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