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Fun with Meshlab

Discussion in 'Digis - Digital Miniatures 3D Modeling' started by RKapuaala, Jun 21, 2012.

  1. RKapuaala Active Member

    Printing 3D figures when you don't know what you're doing is really expensive especially if you want to go to the larger sizes. The best way to cut the costs (even shapways will tell you) is to hallow out your model. Frosted Ultra Detail material allows wall thickness of .3 mm,,, that's less than 1/64th of an inch! That's also a lot of savings if you can get your model with consistent wall thickness'es of that size.
    I spent a lot of time on getting this model as thin walled as I could using a combination of sculptris and meshmixer.
    As you can see it is pretty close, but very irregular and the wall thickness is no where near .3mm but much thicker, especially in some places. I spent 3 days getting that figure hallowed out and although it decreased the cost of the figure in the scales 1:24 to 1:12 it was still way over a hundred bucks in 1:8 scale for frosted detail material, and 200 for FUD. So I finally set out to learn some of the free ware that I had downloaded to see if something would make this procedure faster and more accurate. I tried wall thickness in Hexigon,,,, what a mess! I tried extrusions in Meshmixer. Extrusions in Meshmixer were very good, but took time and to make them work efficiently the model had to be broken in to parts. That would be great, but I've yet to figure out a way to join them back together correctly.
    Finally exasperated, I posted the question in Shapeways forum, and with 12 hours I got a single reply with the exact steps to make a uniform cavity like the one below.
    This is a 1mm wall exactly on a 1:8 scale figure. The price for the frosted Ultra Detailed material to print this figure is below 100 dollars. The added advantage is that with the hallow spaces, it will be easy for me to disarticulate the figure and add some nice joinery so I can cast kits of this figure after adding some hair.
    Here is what you need to make this work.
    Sculptris - To create the model and make modifications to the mesh after inserting the cavity.
    Meshmixer- To help modify the cavity and to combine the cavity with the outer shell
    Meshlab - To create the cavity to export the cavity to an object file.
    Step One
    Create your mesh in sculptris and export it to an Wave front object formatted file.
    Step two
    Import your mesh into Meshmixer. Cut your holes for venting out the support material and for connecting the mesh. To do that follow this procedure:
    A. Select a round spot on the top of the head with the select tool.
    B. click on the modify selection tab and select smooth boundaries. The accept the boundaries if they look nice and round and smooth or increase the smooth amount in the tool properties menu at the side.
    C. type and x to remove the material. Repeat A and B for as many vents as you want to create. Shapeways recommends 2mm venting holes for remving support material.
    D. Last export your modified mesh to a wavefront object file.
    Step Three
    Open up meshlab. Import your previouis mesh into mesh lab and create a unified mesh resample.
    To do that follow the steps below.
    A. After importing click on the filter tab and select the Remeshing, simplification and reconstruction option. Another menu will pop down.
    B. from the menu select Uniform Mesh resampling
    C. A dialogue box will appear. Check the Absolute Distance option.
    D. Set the Precision (abs %) world units parameter (the first text field) to the appropriate precission. For me it was .0569. My mesh was 5.69 units tall.
    E. now set the Offset world units paramter below the first one to the overall thickness of your modle. I set mine to .04 which is equal to about 1mm. I could have set it lower but I am worried about the strength of the walls a modle this size.
    F. Now hit apply.
    Don't worry that your model has disappeared in a cacoon like form. This is the resampled mesh with a consistent volume all the way around your mesh. You need to save the mesh as another object file then exit Meshlab.
    Step Four
    Now open up Meshmixer and import the mesh you created in Meshlab. You are going to modify this mesh so that you can use it as a cavity in your model. To do that follow these steps.
    A. Open the selects paint brush again.
    B. Carefully paint around your original vent holes with a wide enough swatch that when you paint the rest of the mesh you won't accidentally paint inside the hole.
    C. Now paint (select) the rest of the outside surface and double check to see that it is all painted before moving to the next step.
    D. Now pull down the Modify Selection tab again and select smooth boundaries. Then click accept if they look good. Type x to remove the painted area.
    You are now looking at the inside cavity of your model. It will be a uniform distance from the inside walls of your model. You need to export this as a wavefront file before moving to the next step.
    Step Five
    Now that you have saved your cavity you should import the mesh with holes in it and append it to the current scene. Meshmixer has a nice little invisibility tool. Use that to check out your meshes fit before you move on and weld the meshes together. If they are off a little I find it easier to repair in Sculptris but you will need to combine the two meshes to do that and export them to another wavefront obj file.
    After the meshes are all tuned up import them back into meshmixer and weld the holes together. Its that simple. Here is an image of the first part I attempted this proceedure on.
    Its a head, and is good enough to print separately. I went back and did the hole body in its pose.
    I did not include the hair how ever. Just didn't have an image of the bald nude. I will probably do the hair later, but I'm not real happy with it and I think I can do better modeling with clay and make the mold from that.
  2. RKapuaala Active Member

    I just finished sculpting and hallowing out this figure. It took a little more effort to hallow out than the previous one. I think it waqs due to the fact that I didn't do a deep enough negative extrude for the vent holes. 2.jpg
    This one turn out much better than my first sculpt of a man in tights. I am getting more used to the tools now. I find a lot of uses for the extrusion and bridge options in Meshmixer.

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