I was working on a model today and I need to make the black surface into a normal surface so that the ship's cockpit is solid. I am unable to select the black surface. I tried using the flip normals feature, but I was still unable to select it. Any advice on how to make it into a solid is greatly appreciated. Thanks. :)

Edit: Here's the link to the file https://drive.google.com/file/d/1mbTdeeZqhNJx-WlXNqF8mD8QYDSI3Vh_/view?usp=sharing

The weired surface in meshmixer

  • $\begingroup$ Would you consider to attach the file to determine more precisely the failure mode? Even if you don't wish to attach the entire file, use plane cut and cut the plane just below the cockpit. This would maintain any IP considerations for your model. $\endgroup$
    – fred_dot_u
    Apr 26, 2018 at 0:47
  • $\begingroup$ Just added a google drive link. $\endgroup$ Apr 26, 2018 at 4:21
  • 1
    $\begingroup$ Hi Brendan! Have you found and fixed the problem? If so, has the answer below led you to the solution? Please vote to accept the answer so this question is not bumped up once in a while and can be removed from the unanswered question list. You may even add your own solution and accept that after 48 hours! If you have not been able to address the problem please update your question. $\endgroup$
    – 0scar
    Jul 25, 2018 at 13:02

2 Answers 2


With the model file available, I was able to use Edit, Generate Face Groups. This allows one to continue with Select, {set small cursor}, select reversed panels, Edit, Flip Normals.

The above steps resolve the cockpit windows, but meshmixer's Analysis, Inspector shows a sea-urchin-presentation of other flaws, including what appears to be zero thickness walls in some locations.

  • $\begingroup$ I can fix the walls using the make solid feature. I will give this a try and tell you how it goes. $\endgroup$ Apr 26, 2018 at 15:55
  • $\begingroup$ Sometimes the cursor in select mode won't follow the mouse. Any ideas on how to fix this? $\endgroup$ Apr 26, 2018 at 16:49
  • $\begingroup$ I've had that happen when the cursor size is excessive for the area being selected or sometimes when it's lag/delay due to the processing involved. $\endgroup$
    – fred_dot_u
    Apr 26, 2018 at 18:23
  • $\begingroup$ I'm not sure. I have the brush size set to 1 and I'm running meshmixer on an inspiron 15 7000 gaming, which has no problem running 2 games at one, so I don't think that the processing speed is an issue. $\endgroup$ Apr 27, 2018 at 21:28

Opening the file in Meshmixer and then using the Analysis > Inspector tool creates a colorful note, showing LOTS of errors in this model:

Default settings Analysis look at the model

A lot of the magenta errors, a few blue ones. Magenta means "this detail has a small surface area, we'd delete it". Blue means "Here's a hole in the surface, we'd stitch it". The black surface is pink as are some details we want to preserve, so let's change what is considered small: Pushing the Small Thresh to the left (0 mm) removes all the pink and leaves only blue and a few red spots. Like the windscreens, they are red now.

Analysis look with 0mm small threshold

Red means "here are some non-manifold regions, we'd create a surface to fix this". After clicking on Auto Repair All it looks like this, having fixed a lot of these pins but definitely not all of them, as the MeshMixer engine runs against its limits trying to fix this sea urchin. But it is much better.

After Auto Repair

This is still a messed up model containing 416 non-closed shells (only 401 after repair), but now there is a surface at the windows, yet not a very good one. Another example of this model's many errors: the port intake consists of 17 times the same thing copy-pasted next to itself - and it has no lower surface, making this just an open surface and not a solid object

Port intake

In my honest opinion, it would be more effective to fix this with Blender on a vertex level and stitching all the orphaned surfaces together. This model was most likely made for a video game and fixing up game models for 3D printing is at times pretty much recreating it from scratch.


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