Full Version: Auto-retopology algorithms compared

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Yes, looking at the page's instructions, it's a command line tool at the moment. I'm a reasonable Terminal noob on the Mac, so I'd love to see detailed instructions how I could install and use this.

Thanks!

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Hi Metin and Pilou,

you need Developer Tools (C compiler and CMake) to compile the program and the you need also the
listed dependencies compiled, in order to use the program. And yes, Pilou it is a command line program.

Regards
Stefan

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Hi Metin,

> Michael, this could be an interesting algorithm to implement in Moi, don't you think?

Well it's a polygon modeling operation that inputs polygons and output polygons, so it's probably not a great fit for MoI currently with MoI having no polygon modeling functionality in it.

- Michael

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Hi all,
I like to add to this discussion on re-topology "Instant Field Aligned Meshes".....
"....The software converts geometry to uniform quad or triangle meshes, automatically following the curvature of the geometry and snapping edges to sharp features on the model."...etc
http://www.cgchannel.com/2015/11/download-free-auto-retopology-tool-instant-meshes/
http://igl.ethz.ch/projects/instant-meshes/
https://www.foundry.com/trends/design-visualisation/mitsuba-renderer-instant-meshes

regards
O.

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Hi Metin,

to give you a better overview what to do... first install Apple's Developer Tools and it' command line utilities + CMake.
Once done install a package manager like MacPorts or Homebrew, to install the listed dependencies.

After that you simply follow the steps outlined on the Github page to download/compile and use the program.

Hope this helps.

Regards
Stefan

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Hi Ken,

the link you give refers to Instant Meshes, which Mentin and i have mentioned.
Instant Meshes however creates more singularities in polygon meshes than
QuadriFlow, hence the reason why i posted this.

Regards
Stefan

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Hi Stefan,

many thanks for clarifying this issue and apologies for being late !

best wishes
Ken

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Thanks Stefan!

I'm afraid this is a bit too much hassle for me. I've always avoided going the Homebrew route. Back in the good ol' Amiga days I loved to dive deep into such things. Nowadays I've developed enough patience to wait for an easily usable implementation, without hacks and workarounds. :)

But I'm eager to use it as soon as there's a GUI or integration, maybe into Blender. I've started a topic at the Blender Artists forum about it:

https://blenderartists.org/t/new-quad-auto-retopology-algorithm/1124406

If you respond to the thread, it will be bumped up to the top of the thread list again. ;)

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Hi Michael,

OK. I thought it could be an ideal algorithm to implement with regard to your plans for polygon to NURBS conversion inside MoI.

I was thinking of an import dialog offering to retopologize an imported polygon mesh using the algorithm, and add the option of subdivision like in the tools by Max, comparable to Stefan's bunny test.

On the other side, the algorithm could offer perfect quad-poly topology output inside the mesh export dialog, ready for subdivision in a polygon-based 3D editor.

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Hi Metin, from a quick glance it looks like it's more oriented towards processing organic shapes. I'm not sure what would happen if you tried to feed it a CAD model with a mixture of large and small features in it.

- Michael

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Good point, Michael.

Looking at the Siggraph paper...

http://stanford.edu/%7Ejingweih/papers/quadriflow/quadriflow.pdf

... the algorithm includes a sharp edge detection feature:

Image Attachments:
Screen Shot 2018-08-29 at 12.48.12.png 

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Hi Metin,

I understand. ;-) Maybe this topic should be posted at the 3D Coat forum, because
i think they have also Instant Meshes now included in the latest beta(s) of 3D Coat.

Maybe Andrew is faster than the Blender folks?!

Regards
Stefan

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Good suggestion, Stefan, thanks. I'm going to post it at the 3D-Coat forum as well.

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Hi Metin,

> ... the algorithm includes a sharp edge detection feature:

Yes that probably helps some CAD models from just being completely destroyed but I'd think that having a uniform size output is not going to work well with many mechanical objects.

It would be good to see the result on something like this for example:
https://grabcad.com/library/engine-v-twin-4-valve-heads-1

In the paper there is one screenshot of a motorcycle that was converted and it looks pretty weird to me, many areas are mutated pretty significantly.

This isn't to say at all that it's not a useful tool when used where it is intended.

- Michael

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Hi Metin, I've attached an example CAD model here (taken from https://grabcad.com/library/ngoc-mai-tug-boat-1), it would be interesting to see what the output is on these:



- Michael

Attachments:
QuadTest_3dm.zip

Image Attachments:
quad_test_screenshot.jpg 

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Hi Michael,

I've ran your example through QuadriFlow using these parameters:

quadriflow -i examples/Untitled.obj -o examples/untitled_quadriflow.obj -f 3200

The result is pretty bad, and that's an understatement (first one comes from N-gon OBJ, the second from Tri OBJ):





Adding the -sharp option gave me a segfault on the first, and abort trap error on the second run. So no results at all.

Too bad ...

- Fabien

Image Attachments:
Schermafbeelding 2018-08-30 om 09.28.33.png  Schermafbeelding 2018-08-30 om 09.38.30.png 

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Hi Fabien, thanks for testing it. That definitely shows to me that it would be really weird to try and bundle that directly with MoI, since that's the kind of stuff that MoI is good at making.

And that doesn't mean that QuadriFlow is bad, just that it is not intended to work on CAD models.

It's also really cool that the authors set it up to compile on multiple platforms and released it under a permissive license as well.

- Michael

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Come on guys, this algorithm turns technical models into art, what more could you ask for? ;)

OK, I'm convinced. Please keep your polygon mesher as it is, Michael! :D

It's a pity though. For a moment I thought Quadriflow could form the ideal connection between NURBS and quad-poly subdivision modeling.

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Hi Metin, yes over the years I have learned that you often need to take research paper results with a grain of salt, you can't just assume that the results that are shown apply to every situation. Which is fine though, it shouldn't be required that only things that give perfect results in all cases should be published.

But adopting it as a built in feature that users will get surprised by when they use it is a pretty different matter.

- Michael

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Agreed!

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