I'm working on a Lego project where I build models out of Lego bricks in LDD and then import them into Blender via various hoops - inside Blender I then optimize them before loading them into Unity for a small game.

The problem is that Lego has so much geometry inside a big model, because it consists of many small bricks that all have studs and at least 6 sides.

I'm thinking that there must be some kind of tool that can raycast all around outside the model and then delete/group/select all internal faces. Do any of you know of such a tool or where to find more information on this subject? Even just a more correct term would be helpful for my google ventures :)

Here is an image of my model with some of the sides hidden so you can see all the abundant leftover data

Thank you! <3

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    $\begingroup$ relevant blender.stackexchange.com/questions/18916/… $\endgroup$
    – rob
    Commented Oct 3, 2018 at 8:39
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    $\begingroup$ hmmm, I tried creating a Grid fill of boxes and then Joined them altogether. The resultant mesh approximates lots of Lego brick meshes but Selecting Internal Faces did not work and trying to Remove Doubles / Decimate removed to much geometry at least then Select Internal Faces did select internal faces but in a way that further messed up the Mesh. So YMMV $\endgroup$
    – rob
    Commented Oct 3, 2018 at 9:16
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    $\begingroup$ Could you provide a small sample file? Or at least some detail re geometry in a screenshot. $\endgroup$
    – batFINGER
    Commented Oct 3, 2018 at 11:44
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    $\begingroup$ So the "limit selection to visible" was the techinque that has worked the best so far - I rotate all around the models and select with circle select, and then invert selection and delete - but it's not deleting all the inside faces. Maybe they're too close to the outside layer, but it shouldn't be $\endgroup$
    – Dulcis
    Commented Oct 3, 2018 at 12:23
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    $\begingroup$ if you exported it as an ldraw file, you could use MeshLab (available on Ldraw.org). Meshlab can be used to remove the interior of a brick. $\endgroup$
    – Millard
    Commented Oct 12, 2019 at 2:20

1 Answer 1


One trick I used in 3ds max once, was to bake a tiny AO map. Auto uvif you can. Or maybe can vertex color as well.

But basically whatever faces were totally black, I then selected / deleted. Since we're then basically fully hidden from view.


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