How to go from Triangle, Game-Ready Mesh -> Retopology to Quads -> Same UV Map -> Sculpt?

FiftyTifty · Aug 2021

Yeah Skyrim modding woes. I know, I know. Bear with me.

I've got quite the conundrum. I want to create new sculpts, as well as modify the skinning for a specific source mesh. Unfortunately, due to parlour modding and all that, there's no access to the source quad meshes. Only the final, game-ready mesh which is in a proprietary format. Now, getting it converted to FBX and back? That's easy, no problem. But past that, there be dragons.

Sculpting triangles is abhorrent in my experience. So I've been having a shot at 3DS Max's retopology modifier. But I've not quite any idea what I'm doing. Especially with how I'm meant to modify the settings, so that tri-dense areas become quad-dense, and tri-sparse areas become tri-sparse. The only real way I've found to maintain the body shape of the original mesh, was to jack up the polys from 15,000 to 300,000. Which isn't right.

And then there's the issue of the UV maps. There are an uncountable number of mods that rely upon a select few body UV maps. I can only think of two off the top of my head, and they're used for damn near every appearance mod ever. Not only that, the software I found to generate the most perfect morphs for the source mesh, without modifying anything other than vertex positions, requires the UV map to be identical.

3DS Max isn't a hard requirement, it's just what I've got to work with at the moment. So recommended tools/plugins/scripts/whatever, are welcome.

It's a very odd use case, and I've found no information on doing this after searching a bunch. Needless to say, I'm in dire need of insight. Any at all is appreciated.

If it helps, here are a few images showing what I am working with.

Source UV map: https://imgur.com/2kXMLeJ

UV Map punted out by topology modifier: https://imgur.com/3tc2mQg

Source mesh showing problematic topology for the modifier: https://imgur.com/z2vA2jY

Result after blindly tweaking settings to try and keep the overall body shape: https://imgur.com/qcWv0Qn

gnoop · Aug 2021

Every 3d package has an automatic way to turn tris to quads. I did it in Max with some modifier. The name slipped my mind and I run out of subscription currently. In Blender it's ALt+J in edit mode,

You can also use re-meshers . Zbrush one for example and then project UV from original model to re-meshed one. 3d max does it through projection modifier but I prefer Blenders data transfer for that since it works on the fly. Seams areas usually need some manual fixing after projection although.

FiftyTifty · Aug 2021

gnoop said:

Every 3d package has an automatic way to turn tris to quads. I did it in Max with some modifier. The name slipped my mind and I run out of subscription currently. In Blender it's ALt+J in edit mode,
You can also use re-meshers . Zbrush one for example and then project UV from original model to re-meshed one. 3d max does it through projection modifier but I prefer Blenders data transfer for that since it works on the fly. Seams areas usually need some manual fixing after projection although.

Hmm. The Quadify Mesh modifier doesn't change the model at all. Took a look at ZBrush, and that wasn't intuitive at all, it'd need a step-by-step guide as nothing makes sense. I'll see if I can get something going with Blender, thanks.

Edit: Woah. It actually works in Blender. Alt+J didn't do anything, but using right-click -> Tris To Quads did the trick. Thanks a bunch, this is so much better.

FiftyTifty · Aug 2021

New problem found. I use Mudbox for sculpting, and the original mesh comes with split vertices around the UV edges. I welded them before putting them into Mudbox, now I need to split them to get back to the original vertex count.

Is that possible? Failing that, is there a way to bind vertices in Mudbox so they stick together?

thomasp · Aug 2021

If you need them to be the same vertex count, don't you need the original vertex order too? In my experience that's not so straight forward to copy unless the mesh happens to be a single contiguous surface.

Anyway sounds like you'd be better off setting up a morph from the exported, quadrangulated model to a version of that mesh with shape modifications done in mudbox applied, then skin wrapping (Max term) the actual game mesh to that, deforming it into the new desired shape using the morph and re-exporting it.

No idea what Skyrim assets are like though and imgur links always come up empty for me so it's a literal stab in the dark.

FiftyTifty · Aug 2021

thomasp said:

If you need them to be the same vertex count, don't you need the original vertex order too? In my experience that's not so straight forward to copy unless the mesh happens to be a single contiguous surface.

Anyway sounds like you'd be better off setting up a morph from the exported, quadrangulated model to a version of that mesh with shape modifications done in mudbox applied, then skin wrapping (Max term) the actual game mesh to that, deforming it into the new desired shape using the morph and re-exporting it.

No idea what Skyrim assets are like though and imgur links always come up empty for me so it's a literal stab in the dark.

As the game assets are processed to be used by the game engine, the vertices that border the UV islands are split. And they are very weirdly split at that. The torso is split in half, the underside of the breasts are disconnected from the ribcage, and each of the legs separate at the hip.

Worse still, the torso is a separate model from the hands, feet, and head. So there are gaps at the wrists, neck, and ankles.

To make sculpts, the edge vertices need to stick together. As far as I can tell, there's no way to do that outside of merging the edges. But that's all that changes the vertex count. Then they need split again, otherwise the model becomes a chaotic mess when exported into the game's .nif mesh format.

Does skin wrapping work with rather different mesh shapes? I'm intending to create a variety of sculpts, ranging from skinny, to muscular, to fat, to bodybuilder, to obese.

There is an argument that says sod it, and make my own quad based body, with an identical UV map, and identical (or better!) skin weights. But that's a huge undertaking way beyond my current skill-set.

How to go from Triangle, Game-Ready Mesh -> Retopology to Quads -> Same UV Map -> Sculpt?

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