Maya STL import grief

[Tim Leydecker]

Hello,

when importing *.stl files into Maya, there´s this wonderful effect
of each of a mesh´s triangles coming in "unmerged" bloating the file,
corrupting the data.

Simple test:

Create>Polygon Primitives>Sphere

382 vertices

---

Export as Sphere.STL

---

Import that Sphere.STL back in = 2280 vertices

---

Compare Sphere.STL export by imported into Blender = 382 vertices

---


This makes Maya an absolute bomb for handling any *.STL files.

Especially when handing off/over *.STL and then dealing with people that
may not be aware of this (e.g. clients...)

---

Can someone confirm, please?

Cheers,

tim

[Steve Davy]

Yep, I got the exact result you described 🙁

---

From: 'Tim Leydecker' via maya_he3d <maya...@googlegroups.com>
Sent: Friday, December 6, 2024 2:59 AM
To: Maya Group <maya...@googlegroups.com>
Subject: [maya_he3d] Maya STL import grief

 

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[Tim Leydecker]

Thanks for checking!


Now I need to go and find that good old bug report form link
I kept bookmarked/open tab for many years.

Maya is still the backbone for processing files in many
pipelines and editing things for use downstream.

Surprising how this didn´t ring all the alarms already.

*.STL is really *hot* atm with (resin) 3D printing getting so popular
and *.obj is not really an alternative for the people on the Blender
side where many things can go wrong on importing an *.obj there
(depending on import settings).

Microsoft also did a great move hiding away their 3D builder app.

Probably thought let´s replace it with something cooler, then didn´t.

---

I am so glad that history seems to always repeat itself,
that continuity is so comforting once you are dialed in
for survial mode anyway :-)

Expect the worst, brace, brace.

---

Thanks for again for checking,

Cheers,

tim

Am 07.12.2024 um 22:24 schrieb Steve Davy:
> Yep, I got the exact result you described 🙁

> ------------------------------------------------------------------------
> *From:* 'Tim Leydecker' via maya_he3d <maya...@googlegroups.com>
> *Sent:* Friday, December 6, 2024 2:59 AM
> *To:* Maya Group <maya...@googlegroups.com>
> *Subject:* [maya_he3d] Maya STL import grief

> maya_he3d/ba8072db-9bf4-4c30-8957-a2b30ee56508%40gmx.de <https://
> groups.google.com/d/msgid/maya_he3d/ba8072db-9bf4-4c30-8957-
> a2b30ee56508%40gmx.de>.

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[GoLeafsGo]

There is a "merge vertices" option for STL Import.  Open the File -> Import option box, set the File Type to STLImport, and check the file type specific options at the bottom.

-Tim

[Steve Davy]

I don't see any options for STL import file type... at least not in Maya 2023. It says "No options available".

But if that should be there and for some reason isn't, it at least explains the problem.

---

From: maya...@googlegroups.com <maya...@googlegroups.com> on behalf of GoLeafsGo <tim.f...@gmail.com>
Sent: Monday, December 9, 2024 5:34 AM
To: maya_he3d <maya...@googlegroups.com>
Subject: Re: [maya_he3d] Maya STL import grief

 

To view this discussion visit https://groups.google.com/d/msgid/maya_he3d/466d4116-6300-429a-ab69-d73ee07a313cn%40googlegroups.com.

[GoLeafsGo]

Ah :-(  Yeah, there was a bug where the STL translator wasn't registering itself correctly and Maya didn't know about it's script to create the options UI.  I'd forgotten about that even though I logged the bug.

On import there's really only two options though and it's not hard to set the options yourself, just run this:  

optionVar -sv "STLImportOptions" ";mergeVertices=1;vertexTolerance=0.01;"

You can turn merging on or off, and set the tolerance it uses to decide what verts to merge, those are the only two options in your version of Maya.

-Tim

[Tim Leydecker]

It seems my previous mail didn´t go through.

Thanks for sharing those importer options:

optionVar -sv "STLImportOptions" ";mergeVertices=1;vertexTolerance=0.01;"

---

I ran a the test with two spheres exported from Maya 2020.4
as *.stl and imported into Blender 4.3

On import into Blender, those spheres come in as one object
and vertices/shells are merged correctly, meaning that the
two sphere shells are not merged in a non-manifold way where
they touch.

This implies that the Maya Exporter is writing out useful data
but the Maya Importer is flawed/limited.

I´ll give the STLImportOptions a go but I suspect it will
create non-manifold geometry if it´s a simple merge by distance
function under the hood instead of correctly reading the file...

Let me see.

Two spheres touching only on one vertice should result in
at least two shells, not one shells merged into non-manifold geo.


See below for "two spheres" test scenario for more detail

---



//That previous mail that was lost somewhere



---

Thanks for checking through the *.stl Import Options.

I don´t have this "Merge vertices" Option in 2020.4 either.

---

Worth testing if this works for shells that aren´t meant to
be merged and 2 vertices of seperate shells at same position
ending up getting merged

or

if the Import respects original shells as one would actually need.

E.g. is the file import really correct?


Manually merging vertices by (tiny) distance breaks the desired
results when using that as a workaround pre-Import Option setting.

---

Would be good to know if that Importer Option is actually
respecting shells or just merging by (tiny) distance as a
limited hotfix, too.

---

Test for 2024:

Create>Polygon Primitives>Sphere

Duplicate Sphere

Translate Duplicate by Y=2 (two spheres will touch on 1 top/bottom vertice)

Export both spheres together as *.stl

Re-Import with "Merge Vertices" and check if those vertices are now
merged...

---


Also worth checking how the Normals/Shading is affected in general.

---


Cheers,

tim

P.S: Sorry, can´t do this test at home, only have 2020.x at home.

[Tim Leydecker]

Am 09.12.2024 um 21:04 schrieb Steve Davy:
> I don't see any options for STL import file type... at least not in Maya
> 2023. It says "No options available".
>
> But if that should be there and for some reason isn't, it at least
> explains the problem.

> ------------------------------------------------------------------------
> *From:* maya...@googlegroups.com <maya...@googlegroups.com> on
> behalf of GoLeafsGo <tim.f...@gmail.com>
> *Sent:* Monday, December 9, 2024 5:34 AM
> *To:* maya_he3d <maya...@googlegroups.com>
> *Subject:* Re: [maya_he3d] Maya STL import grief

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