topic Re: Boolean differences and offsets in Meshmixer Forum

Boolean differences and offsets

Anonymous — Wed, 15 Apr 2020 02:43:50 GMT

I need some help. I have a dental Model (pink) and a dental splint(green) and an attachment that I need to add to the splint (purple). the problem is I need the splint to be offset from the tooth surface by .1mm. As you can see in the attached image you can see it works except for the area that that attachment is placed. how can I offset that area so i can have an accurate fitting splint?

Re: Boolean differences and offsets

hfcandrew — Wed, 15 Apr 2020 14:21:28 GMT

Before you do your boolean difference, scale your model bigger with an offset: Select all>Edit>Offset (Set distance to 0.1mm)

Re: Boolean differences and offsets

Anonymous — Wed, 15 Apr 2020 19:33:26 GMT

Thanks for the suggestion, I tried that and I get this error.

Re: Boolean differences and offsets

hfcandrew — Wed, 15 Apr 2020 19:41:25 GMT

Every mesh is so different, it is impossible to tell what the issue is without the .stls. can you post them? this tool can fail if it it not solid and has non-manifold pieces or flipped normals etc.

Re: Boolean differences and offsets

Anonymous — Wed, 15 Apr 2020 20:09:42 GMT

I tried making the dental model a solid and still have the same issue.

Re: Boolean differences and offsets

hfcandrew — Thu, 16 Apr 2020 03:20:08 GMT

Sorry, I always have trouble following what people want done.

Do want Shell {Max1}.stt to boolean union to purple piece in your original post? If so can you also attach that model?

Re: Boolean differences and offsets

Anonymous — Thu, 16 Apr 2020 15:23:15 GMT

Sorry that was my bad I need to be the boolean difference between the shell and the remove undercuts model. I need the remove undercuts model to remove pieces of the shell model. does that help?

Re: Boolean differences and offsets

hfcandrew — Thu, 16 Apr 2020 20:49:28 GMT

Are you sure to sent me the correct pair of models? The teeth looks nothing the same.

And in complex geometry such as teeth it will make hundred of subtraction boundaries instead of like 2 or 3, thus more likely to fail.

https://help.autodesk.com/view/MSHMXR/2019/ENU/?guid=GUID-355503DE-889B-4168-8398-084F9BBD508B

Also the order in which you select the objects matters, so for this you will want to select "Shell" then "undercut".

Re: Boolean differences and offsets

Anonymous — Thu, 16 Apr 2020 21:12:40 GMT

ok lets try these two files. I need "teeth" to subtract shell.

Re: Boolean differences and offsets

hfcandrew — Fri, 17 Apr 2020 02:43:15 GMT

This looks better, looks like it should work, but it is still failing. There are a few oddities in that 'shell' had any extra body in it. Go Edit>Separate Shells. So I deleted that chunk out, but it still failed.

Then also there are hole in the tips of the molars punched through on 'shell' tool but the tool doesn't even fail at those points anyways.

A good test to see if that model will work in any circumstance at all is to try to same operation but using a simple primative such as the sphere against both object. If a simple shape doesn't work for both objects, then using both objects together certainly will not work.

I can get a boolean subtraction to work with a sphere and 'teeth' but not for a sphere and 'shell'.

I'm stumped again! This looks like another job again for our resident MM superhero @Anonymous

Sorry my friend, I'm stuck too!

Re: Boolean differences and offsets

Anonymous — Mon, 20 Apr 2020 08:43:02 GMT

@Anonymous

Run SeparateShells on your Shell object and discard the interior cavity object after that.

Run MakeSolid on the Teeth object. Switch to Accurate mode and set a higher SolidAccuracy and MeshDensity. Set OffsetDistance to the value the gap between Shell object and Teeth shall be finally:

SELECT the "contact surface" on your Shell object and Transform it to give a clear intersection towards the Teeth (the problem with Booleans are redundant surfaces resulting in a never ending number of intersections)

Now run BooleanDifference on Shell - Solid result:

Removing not needed particles there's a constant gap between Shell and Teeth now:

Re: Boolean differences and offsets

Anonymous — Wed, 26 Aug 2020 13:19:53 GMT

I have problems like Paul performing B-diff between dental model before and after wax-up.

I solidified scansion before trying B-diff
I inspect two different meshing and a lot of red and blue lines. (Unfortunately I don't understand what red an blue line are! i think errors but i can't check)

If I accept I had "tools error" window

suggestion?

Re: Boolean differences and offsets

hfcandrew — Wed, 26 Aug 2020 13:31:46 GMT

Red lines show non-manifold triangles.

Blue lines show open boundaries.

These can be corrected with the inspector tool: https://help.autodesk.com/view/MSHMXR/2019/ENU/?guid=GUID-83BC663B-FA1C-46D3-8C2F-82EB6892DFC3

Try that nad see if the above mentioned process works.