Best Way to Hollow out Objects

I need a way to accurately hollow out my models. I've tried creating a box inside my model and inverting the normals but i sumtimes get erors from shapeways when ordering the model because its too thin ! I use 3ds max and have tried to create a shell aswell but my models are too complicated and it causes a lot of problems with my mesh.

So i was wondering how everyone else hollows out their models? Whats the best way to do it!? Thanks!

Hey there emcfarlane;


I read your post shortly after you put in up but was hesitant to reply because I don't use 3DS MAX.

However since no one else is tossing anything out, I'll give you a little info on how I go about it.

I use Blender and have used several different methodologies to accomplish the 'hollowing' of a model.

First off; before you try to hollow out your model, always make sure of the following:
1) Your mesh is manifold. [CTRL+ALT+SHIFT+M]
2) Your normals are properly oriented. [CTRL+N]
3) That you apply any scale and rotation [CTRL-A]

Method 1
Blender has a built in Python script called 'Solidify Selection' and there is another that you can down load called 'Solidify mesh' that both create an inner wall relative to the outer surface based on input from you. I use this every once in a while as the results can be sketchy.

Method 2
Another approach I have employed in Blender is Extruding the entire surface, and then scaling relitive to the Normals.
[E] [Extrude Regon] [ESC] and then [ALT+S]
This is slightly different than normal scaling and I have had fairly good results with it.

Method 3
In a few cases where the complexity of the mesh was rather intense, I have simply made a copy of the entire mesh [Shift+D], and then scaled it down. or [ALT+S] and then actually edited the 'Inner' mesh to remove portions that were too thin and any portions of the mesh that intersect. (Overlap). then rebuld the mesh into a single model [CTRL+J] and finally, re-orient the normals with [CTRL+N]


You can always try posting a copy of your model in the forums to see if someone will help you fix it as well.

I don't know 3DS MAX either, but in KeyCreator, I shell the solid then create a solid of the same dimensions as the hole I made, with the thickness I specified in the shelling to close it back up.

Thanks WiKKiDWidgets and Youknowwho4eva.

I'll try blender always found it too complicated before, But thanks for the fast replies. Great forum.

What I relly wanted to know if theres a method, script or program that will hollow a mesh out to exactly 1mm. That would be great!

hehe, ya baby! That would be nice!!

But I think the issue facing a script would be that most 3D formats do not contain dimensional data. I.e. A model That I specify as 10mmx10mmx10mm could just as well be 10'x10'x10' as far as most applications are concerned. (One of the primary differences between modeling tools and CAD software). I'm surprised Meshlab and Accutrans don't have a nifty feature like that.

Mmm stil can't relly find a great way to hollow out objects. Anyone else with other ideas? :confused

By the way is the printing thickness in all ways. For example could we have a really flat object thats say 0.5 mm high but long enough width and height. Also whats the meterial restrictions on stainless steel havent seen anything about it?
Thanks for help in advance

I actually did the same and it does seem to work fine. I got no errors on the first submit. I haven't gotten the result back though, so I don't know how it will turn out. But, an inverted box seems like a valid way to me. Shell is a way to go, but it can cause overlapping polygons.

To hand you a solution for the standard checks. In max there is a "STL check" modifier. If your model passes this check, it should be manifold and closed and it should pass most shapeways checks. STL check can also highlight the problem area's for you. Do note it's better to keep the object manifold while you're making it than trying to fix it at the end.

Thickness is of course not checked in this way, but you might be able to create some volumetric material to detect problems in a render of your object. I go as thin as about 0.8 mm on the model I submitted yesterday.

Hmm your wish list solution, My software I can thicken a sheet body. So if I had a solid, exploded it into faces, and thickened those to 1 mm, theoretically it would do what your asking for. Is it possible for you to copy your model, shrink it by a percentage, then subtract it from the original? it wouldn't be uniform but it'd be close.

No not possible. Find best way is too manually create inside of model. It takes time but if done right works. Sorry I havent replied have been frustaded with my models as shapeways has not delivered them! Mix ups or something.

I work with wings 3d and I am a newbie.
in wings there is the "intrude" command which seems to hollow out nicely.
But I have to measure afterwards. if the measure is not ok I have to go back
and do it again.

unfortunately I saved the hollowed model for a 1/72 scale model which turned out too expensive. then I had to size it to 1/144 and the walls became too thin.
This I resolved by
- select all faces
- click away all outer faces, so you have selected all faces on the inside of the
hollow
- "move normal" of these faces and move them toward the 0-point.
be sure your model has the 0-point at it's center.

since this is all relative, not all walls grow the same amount...

Regards,
Ronald van Aalst

In max you can duplicate the outermodel. Next scale the innermodel or better relax the innermodel.. Then make a compound where you substract model b from model A ..
For complicated models you have to do a lot of cleaning up .keep some copies from your original models before you make the compound .

Actually, you don't need to make a compound. Just attaching the outside and inside is enough. And there is also modifier which does this all at once, shell.

MeshLab is by far the most effective tool I've tried for this.

The filter you're looking for is called "Uniform Mesh Resampling." Run it sort of like my tutorial here, except that instead of doing it twice, to make an outer and an inner shell, you just do it once and use the inner shell.

If, and only if, you're sure that your model is manifold, then you can also specify a negative "Offset" to the filter, exactly equal to (minus) your desired wall thickness, and you will receive only the inner shell, with no outer shell to delete.

Making the hole from inside to outside, so that the material can drain, is up to you. PLEASE don't just trap material - Shapeways won't charge you for it because it won't show up in volume calculations, but they lose it just the same, whereas all other poweder is reused.

I have a couple solid parts here that cost out to $35.00 each to print so I figure a project to learn how to hollow them out would be a good lesson and save me some $$$ at the same time. I have reviewed the tutorials here and read the forum threads on the subject and my question is, Do the basic steps involved hold true while hollowing out a part as a cut away ? Meaning one face (base) would end up completely open or is there a different set of steps to follow. I would compare to what I am after as an end result would be something like a bowl that has the open face rather than a hollow ball that is completely inclosed with the outer layer.

Cheers

Shapeways has a very sophisticated software for the MeshMedic - i would like to suggest adding an option to the upload page like this:

[ ] Please manually fix my model if the upload fails.
Please also hollow my model by [ X ] mm .

That software will hollow your model exactly the amount of mm you ask it across any curve of the model in a very efficient way - this way you get to have and offer an AFFORDABLE model in terms of printing cost.

Otherwise i doubt any other hollowing methods could give you an exact volume/price control of your model.

Here is an example :







Cheers,
Dizingof

Yes that is an interesting option. Though not very easy to build. I do have it on my wish list.

- Robert

I am certainly not the one to be handing out tech advice, but I will offer my meager suggestion here. I work in AutoCAD 2009. The one time I ever tried this, I just used the Scale function, scaled to the center of the piece, then Subtract to remove the smaller solid from the larger. Worked great!

I've never used other software, but if you could try something similar, just using a minimally scaled down copy of your solid to subtract from your original, it might work. You can even take measurements point ot point from the smaller to larger piece before Subtracting to ensure thickness. This solution took me about a minute to perform.

Scaling really isn't the best option I think, since it generally only works with simple models and the thickness might vary a lot. In 3DS max you can use the shell modifier to easily create a thin layer version of your object. That way is a lot more rigid, though it might still need some manual fixing.

I like the Meshlab technique noted above, but if I have a complicated model, I'll use Rhino. Try a negative offset mesh with the option solidify.

hope this helps,
Troy

Hi understand the concept. i have found tutorials for that process:
https://www.shapeways.com/tutorials/creating-hollow-objects.

I come from an art background and actually bought zbrush to avoid learning blender. I surely can not afford rhino or 3dmax or maya... at the moment. I will search for 'subtraction' in zbrush. If i can not find it I will start the blender tutorials...rrrr... To be frank, blender looks like somebody threw up a bunch of letter and numbers. To all software designers --- Less is more----

Problem with being a noob is that I get lost unless i can find the specific tutorial to teach me how to subtract in the specific software with pictures.

Below is a message that i found describing the blender process that i will attempt to follow:












I use Blender and have used several different methodologies to accomplish the 'hollowing' of a model.

First off; before you try to hollow out your model, always make sure of the following:
(All commands are for Blender)

1) Your mesh is manifold. [CTRL+ALT+SHIFT+M]
2) Your normals are properly oriented. [CTRL+N]
3) That you apply any scale and rotation [CTRL-A]

Method 1
Blender has a built in Python script called 'Solidify Selection' and there is another that you can down load called 'Solidify mesh' that both create an inner wall relative to the outer surface based on input from you. I use this every once in a while as the results can be sketchy.

Method 2
Another approach I have employed in Blender is Extruding the entire surface, and then scaling relitive to the Normals.
[E] [Extrude Regon] [ESC] and then [ALT+S]
This is slightly different than normal scaling and I have had fairly good results with it.

Method 3
In a few cases where the complexity of the mesh was rather intense, I have simply made a copy of the entire mesh [Shift+D], and then scaled it down. or [ALT+S] and then actually edited the 'Inner' mesh to remove portions that were too thin and any portions of the mesh that intersect. (Overlap). then rebuld the mesh into a single model [CTRL+J] and finally, re-orient the normals with [CTRL+N]


You can always try posting a copy of your model in the forums to see if someone will help you fix it as well.