Meshmixer Separate Shells: too many separate shells! (expecting 2 result is 166)

[jamesbeckett73]

Hi there, my first post:

I split a model into two parts using "plane cut" - with the option "select (keep both)"

When "separate shells" my model breaks into 166 in place of expected 2!! This is after heavy processing time.

I break the model down into a smaller selection to try and trace the problem and observe the same effect, albeit with fewer parts due to smaller selection. Screen shot shows smaller selection version.

Any advice appreciated to achieve a simple two shell separation...

Meshmixer 3.5.474 and OS High Sierra 10.13.5

[jamesbeckett73]

Been at this for days now, but it seems I am able to solve through:

Analysis > Inspector > Flat Fill

so can now "Separate Shells" into the desired amount, due to a fixing geometry.

The new problem created is the messing up of my texture, and on export means my next program is unable to import the texture in its natural state. Seen in the attachment is a pink fill which I suspect to be the culprit.

I experimented with every parameter in Inspector to no avail....

ARgggggggggrrggg.

Any help appreciated.

[Anonymous]

The first thing is to make sure whether you're dealing with a single surface. Scans (think this is some kind of surface reconstruction) often own outliers (small surfaces not connected to the either surface):

Run EDIT/SeparateShells on your source mesh. If MM finds several shells discard all but the either surface.

On this single surface start (do NOT do AutoRepairAll on a single sided surface) Inspector. If there's only a single blue marker sphere all is fine and Cancel Inspector.

If there are more markers either: Click all the spheres but the one pointing to the outer boundary one by one to fix the detected issues (unfortunately there's no RepairAllBut the outer boundary).

Or: Switch of texture rendering by dragging the default shader (next to the + ) from SHADERS onto your object for a better view of face groups (your texture is still kept). Make sure you're on MeshColorMode= GroupColor(Default) (see Preferences). Now SELECT a piece at the boundary of the mesh and do Modify/CreateFaceGroup. If there are more than one group at the boundary Inspector will fill the hole with a new face group. So you might do AutoRepairAll in Inspector, go to SELECT, select this infill group by double click and discard it.

Now a planar cut of a single surface without inside errors might still result in problems if there are undercuts cut by  PlaneCut due to surface noise. E.g. at extreme:

If you'd do the cut in CutType=Slice(KeepBoth) and you'd do Separate after that cut the upper example will result in 5 objects. Although it's not ideal one might solve this doing PlaneCut in CutType=SliceGroups. This results in this:

Now SELECT the main group (e.g. the white one) by double click:

Hit Y to separate:

Now there's a non connected piece at the brown side (the undercut closest to the viewer). So make the brown object the active one and do EDIT/SeparateShells:

Activate all the split parts from brown + the white object, run Combine and finally EDIT/CloseCracks on the combined object. Now there are two objects only (transformed for a better view):

Note about MM's texture handling:

As soon as MM needs to "invent" textures by interpolation it creates a second texture image for areas where it could not simply split existing faces and it's texture snippet along. Seems your target application doesn't support more than one texture per file. So you need to find an app joining several textures to a single texture map. MM doesn't do this.

[jamesbeckett73]

Thank you Magweb, all clear and I am able to go further.

A question if it is the appropriate place - after "separating shells" to 6, I have a dramatically reduced CPU performance. I have plenty of extra drive space and run 16Gig ram (.mix file is 194mb). I read your response to this post:

https://forums.autodesk.com/t5/meshmixer/meshmixer-is-killing-my-cpu/td-p/8462843

Any further tips or a hunch why things slow down so much?

Thanks in advance,

[Anonymous]

Here a single shell textured mesh with a 200MB textured .obj file and a texture image of 17.5MB gives a memory load of about 2GB. This load increases quickly if one does a split (depends much on the number of pieces ).

So clear the UndoHistory frequently. E.g. the undo of the step to split my example mesh into 2 pieces needs about 0.5GB memory which may be released clearing the UndoHistory.

Another thing which might slow down your system is MM's autosaving interval. By default it saves the current scene each 60 seconds. Working with larger files you might want to change this default setting. To do it you'll need to edit meshmixer.ini while MM is down: See this thread

[Anonymous]

DOWNLOAD    3DBuilder form microsoft Store its insane for splitting models  it auto fixes ur model perfectly  and you can split just like meshmixer iwht the keep both options 

[Anonymous]

Once you septerate your parts oyull see them at the bottom right in a tab you can just drag out of the app right into your slicer os drag half of the model out into slicer slice it then get other half actually super dman cool and no one uses it

[Anonymous]

can also subtract another object form its nterseciton so you could make action figure pins and such for the arms SOOOOOOOOOOOOOOOOOOOOOOOOOOOO much easier and better than meshmixes dont think just try t its free on microsoft store im having a blast with it  wotn drag into Creality software but does Drag and drop into CURA perfectly i actually like having all mypieces in a seperate app i can just click and drag into the slicer from super handy best app WINDOWS got