1. #1
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    May 2012

    Default Hollowing Out a Mesh / Creating and Combining Shells

    I'd like to hollow out one of my 3D meshes that I plan to print via Shapeways. I've seen multiple references recommending doing this to cut down on the cost of materials, but I haven't been able to find many tutorials for doing so.

    Here's the process I've used so far:

    • Sculptris to create the model
    • MeshLab to save the exported OBJ as an STL
    • NetFabb to clean up the mesh and set the scale

    The full version of NetFabb ($900) has a simple point and click function for hollowing out a model. However, I'm looking for cheaper alternatives. Below is a link to a tutorial for hollowing out a mesh using the free versions of MeshLab and NetFabb.


    (I print the whole URL so you can see what you're clicking on.)

    The problem is that NetFabb wants to work with an STL file. Once you hollow out the model, you have to "punch" a hole through the model somewhere. As you know, Sculptris doesn't handle STL files. (I suppose I could save it as an OBJ file, but that's a lot of exporting back and forth between file types.) So I can't use Sculptris to punch the hole through the hollowed out model.

    Does anybody know of free/inexpensive software for punching a hole through the hollowed out mesh saved as an STL file? Or is there a better way to hollow out a Sculptris model?


    (I tired doing a forum search with no positive results.)
    Last edited by Dr. Soupie; 05-17-12 at 12:31 PM.

  2. #2
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    Jun 2011


    Wings3d has an "Intrude" function. You select any polygon, Right-click and select Intrude, then drag the mouse just a little and it will build a Manifold skin, However, you may have problems depending on your model. First, Wings3d gets real slow after about 300k polys, and, as Intrude uses the face-normals for reference, you may end up with some polygons crossing on the inside of the model. There might be a fix for this in Meshlab...

  3. #3
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    Dec 2011


    Can't he just bridge the hole in meshmixer ?

  4. #4
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    Jun 2011

    Default re

    His problem is just the opposite, I've never tried 3D-printing but I've read about it. The idea is to Hollow your model out, making just an outer shell to print ... less plastic, less money to print. In this case Wings3d -Intrude, I think blender has Solidify Modifier will do something similar. As a final resort, Blender's booleans work well also. This will leave the skin thicker, but It should be Manifold!

    Red maybe right though, I do believe Meshmixer has some tools geared towards 3D-printing, including a way to have it Printed from their site ...... As far as conversion, Meshlab should have that covered ...

  5. #5
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    Dec 2007


    Depending on how detailed your mesh is, or how much you would be losing by going back a step,you can do it right in ZB. Just turn your mesh into a DynaMesh. Make sure project is on and your resolution is high enough tomretain as much of the detail as you can. Then use insert bruschetta (cube or cylinder) on the bottom were you would want a hole (not sure if you need to press Alt to make it a subtract but I do) then, unmask but don't remesh. Instead click on Make Shell after messing with the thickness. If your mesh has a lot of detail, it may take some time and you'll have to use a bit of guess work how think to ,are it, but it works a treat. If you've lost some detail, just go back and result it. Then make sure you decimate before exporting - done.

  6. #6
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    Apr 2004


    Meshmixer v7u3 creates same junk on extrude with negative offset as Max 2012. Dynamesh is the best so far. By eye of course since there won't be any precise Negative Offset in Normal Direction tool probably. Combine in Meshlab or Max, boolean in Max to punch a drainage hole. The guy who did the tutorial in Max also does it by eye, pushing in the inside part by hand.
    Meshlab loves to crash on higher precision values that would allow build higher-res inside surface.

    Better than ZEdit Pro for 2500USD or Netfabb for 700USD.

  7. #7

    Default shelling for prototyping

    Don't know if this is still of any use, but I've got a workflow that is working reasonable well for me, if somewhat convoluted!

    1. export outer mesh from maya/zbrush - good idea to decimate if it's got lots of detail.
    2. import into Meshlab (free)
    3. do a: Filter>Remeshing..>Uniform Mesh Resampling - precision 0.3 (lower humber takes longer), Offset -.8 (for 0.8mm wall thickness) check> Clean and >Multisample... ...and wait.
    4. export inner shell as obj
    5. decimate in Zbush.
    6. import into Maya, I do a clean up here, delete scraggly bits merge etc, really rough, then flip the normals of the inner shell and combine the 2 meshes.
    7. you may want to boolean a couple of holes trough the mesh too, otherwise shapeways still reads it as a solid form not a thin shell.
    8. do a check and clean in NetFabb (free) export and upload.

    the Maya steps are only beacause it's what im used to and where i built the original Objs

    this is working for me at reducing my print costs heaps!! like 50% or more

  8. #8
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    Apr 2013

    Default Curvy

    I've been looking at one called Curvy. It's possible to export it to that, make a copy, reduce it, move it into place, adjust [make the parent semi transparent and coloured, and adjust the child to fit], then subtract the child. The developer seems to think it'll work. It's about £50 UK money [around $80??].

    Does anyone know of a free program [for a Mac] which will work??


    PS The 3D program Cheetah [$100] allows for shell thickening. I think Cheetah is only for Macs, though.

    Last edited by McBryde; 04-10-13 at 05:37 AM.

  9. #9
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    Jun 2013

    Default boolean with blender, without color

    Name: 'Muli Boolean Union'
    Blender: 242
    Group: 'Misc'
    Tooltip: 'trying'
    from Blender import *
    from Blender import Draw, Scene, Object
    from Blender.Mathutils import Rand
    # runs through all objects and boolean:union them together
    def supb(scn, sel):
    i = 0
    for objss in sel:
    if i == 0:
    objFirst = objss
    i = 1
    else: # i == 1
    if i == 1:
    objSecond = objss
    i = 2

    # adding modifier
    mods = objFirst.modifiers # adding a modifier
    mod = mods.append(Modifier.Types.BOOLEAN) # with boolean
    mod[Modifier.Settings.OPERATION] = 1 # and union

    # doing the modifier
    mod[Modifier.Settings.OBJECT] = objSecond # adding the element to the modifier
    objFirst.makeDisplayList() # doing the modifier

    # deleting the old two
    # scn.unlink( objFirst )
    scn.unlink( objSecond )
    i = 3
    Window.RedrawAll() #??
    def main():
    scn = Scene.GetCurrent()
    if not scn.objects.context:

    sel = scn.objects.context
    objects = [ob for ob in scn.objects.context]
    Count = len(objects)
    # i = 0
    # while i < 10:
    # i = i + 1
    f = Count
    for i in range(0, f):
    supb( scn, sel )
    sel = scn.objects.context


    if __name__ == '__main__':
    i use this script for Multi Union booleoan objects."
    The Color of the objects get lost, thought finally there is only one object."
    have fun

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