Why do so Many Auto-retop Tools Spiral and Why do People Not Seem to Care?

flamingmonkey93 · May 31 2024

For context, my job involves taking 3d scans of furniture and retopping them to a more useable, renderable state. We do not however bring in or use colour scan data due to how a single piece of furniture will have numerous kinds of materials applied to it.
Naturally this is tedious. There are numerous ways to speed things up, with much more efficient tools and software like Topogun etc.

However, when it comes to just overall fully automatic retopping tools these always leave some sort of unsightly, and often unworkable spiralling geometry.

So, to my question above really.
You see so many of these auto-retopping tools and the praises sung by them, but if they constantly give spiralling geometry is this a result that is not actually cared about/effects the workflow? or is there just more work needed to be done from out side in order to make these auto-retopping tools work?

e.g. Are the spirals a non-issue, because of how the diffuse is brought in and baked onto the mesh. Or that they're painted in 3D with the likes of substance and thus weird seam placements are a thing of the past.

poopipe · May 31 2024

if you're looking at conventional (non-ML) algorithms there really aren't any very good ones for inferring a direction of flow from an arbitrary cloud of points cos it's just not a thing you can express mathematically.

ML is probably the answer to this one. it's an ideally suited problem ...
That of course means you'll be waiting a while for anything decent to show up. Nobody's funding anything useful when there's money to be made generating porn and gathering personal data from users

I've not poked around much in several years but zbrush's guide painting was probably the best way to handle the issue in practice.

gnoop · May 31 2024

If a 3d scan is really hi res with sharp edges Zbrush Zremesher with "detect edges" on does pretty nice job actually without much of spiraling edge loops. As well as 3d max one. The issue are things like blades with triangle profile where it can't recognize the cutting edge . Boxes and cylinders with holes are often sort of okish.

Also i prefer to use topology brush with Shift to draw straight lines on hard surface objects . Zremesher works with any curve brush.

iam717 · Jun 1 2024

zbrush's guide painting was probably the best way to handle the issue in practice.

Yeah, & op, when i care to it i do the zremesh,topogun route to cut out the b.s. if you want a method to try, but i agree.

Couldn't they just use patterned geo with proper topology to be unified with the math-algorithm they use(like do it like this, patterning and not spiraling,"lazy-method")? like cylinders for clothing and pretty much anything else, except for some hard-surface works. (+ abnormal/unique creations/cases).

Michael Knubben · Jun 1 2024

The spirals are an issue, it's just a hard problem to solve automatically. Giving the algorithm facegroups/materials to cut the mesh up into multiple parts and to mark hard edges helps, but it's still hard to get a usable mesh out without manual fixing.

I use Exoside's Quadremesher (the same algorithm as Zbrush's) and it's nice, but needs manual work to guide it.

Shrike · Jun 11 2024

I would look into houdini, they recently were showing some good looking scan optimization features I think but never did it myself

Eric Chadwick · Jun 12 2024

3ds Max has some really good options lately for tweaking how the retopology is generated, worth a look

https://www.youtube.com/watch?v=Pg2Nm-fwyME

Why do so Many Auto-retop Tools Spiral and Why do People Not Seem to Care?

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