Unwrapping mesh to existing UV map?
I'm just a lowly modder, and some of the game meshes I'm trying to edit have really poor geometry, to the point of not really being modifiable in any significant way. My current problem model, is a tiger which I'm repurposing into a head for a human character. It's not symmetrical, lots of split vertices, and the triangles are extremely wonky on certain parts.
Is there a proper workflow, for making a sculpt around a template, then UV unwrapping in the exact same way the original was unwrapped? I need to keep the same texture files, as making new ones is way beyond my skills, and break compatibility with texture replacers.
Here's the diffuse file, for reference: https://i.imgur.com/WatlguZ.png
I prefer using Maya in general, but can also use 3DS Max.
Replies
Can you show the model you're starting from? It may not be as unusable as you think.
Generally it's tough to reuse an existing uv layout for a character mesh. Hard surface models tend to be more forgiving, as with trim sheets.
Here's a great example of a modular character workflow:
http://wiki.polycount.com/wiki/SkankerzeroModularCharacterSystem
Oh, of course. Don't know why I left that out: https://www.mediafire.com/file/8xa803okneggd5q/Big_Cat.7z/file
I've included the tiger mesh I've had endless grief with, male player head + torso, and female player head + torso. The workflow is to manipulate the skeleton as much as possible, so that the head intersects with the neck gap and completely covers it. Then try and get as nice a flow into the torso as possible, transfer skin weights from the torso, and hope to go they look OK.
But, uh, they look awful for animal meshes that don't have much detail. The stretching of the neck bones are horrific. And there are vertex gaps galore, so I can't really do detailed editing. Merging the vertices, sculpting, then exporting back causes massive issues with the UVs, and of course, loses the skinning.
Can't open a zip here on my phone. How about an image or two?
You'll probably have an easier time to retopo the original model, unwrap it however you please, and then bake the original textures onto your new model.
The key information on the original is the form of the model, the textures, and the rigging. That is all stuff you can easily bake onto a new model with clean geometry and whatever UV's you want.
If you are using maya, look into the NG skin tools plugin for easy rigging toolset. Copy/paste skin weights is super easy with that plugin. Maybe default tools are fine too but its been so long since I used them I dont recall.
For baking the textures my go to is Marmoset Toolbag. Again, probably default tools for that may be fine but I don't remember anymore. But baking the PBR textures - or any sort of textures - from one model to another is really easy thing to do. Just follow standard baking guidelines and essentially you can transfer textures from any model to another - most of the time thats my preferred workflow when editing an existing model.
Fair deuce.
https://i.imgur.com/g5rRinD.png
https://i.imgur.com/0oMftam.png
https://i.imgur.com/l3995uX.png
https://i.imgur.com/HODfCA4.png
IME, the default tools for 3DS Max and Maya are really bleh at best, for copying skin weights. I'll check out NG.
Being able to transfer textures from different models is perfect. For the retopology, I'm guessing a specific tool will be needed for as close to a 1+1 match as possible, rather than sculpting around the original mesh to get something similar? My process for sculpting is to fire up Mudbox, which is pretty basic as far as tools go compared to ZBrush, afaik.
The Polycount guide for baking is a right ordeal, working with multiple source meshes. Is there a more appropriate guide for doing this? It's very technical as well, and I've not done baking before either.
Another stumbling block, is weighting the fur billboards. Especially on more "fluffy" creatures, such as male lions, where there are loads billboards intersecting polygons around the neck and cranium. What's the run-down with that? In my experience, copying skin weights from a model to polygons that stretch away are...Well, very, very stretchy when animated.
Thanks for the info, it's good to know that there's definitely a way to solve these issues.
Well, you first have to manage expectations. You are tackling many different complicated disciplines here. There is quite a bit to learn in order to be able to do a good job with all these different task.
For weighting the fur planes, I'd set the initial bind settings to something like "closest joint" and then limit the influence to one joint. Also with NG skin tools, you can work with layers like in photoshop, so you could start with a binding like that and then also copy weights from the main model on a separate layer, and try blending the layers together and see how that works out. Just spitball idea.
For retopo and baking - it's pretty simple really. Think of the original model as a template. You can set it to a "live" mesh in maya, then use the quad draw tool to retopo directly on it. It's pretty efficient with a bit of practice. There is dedicated retopo tools but from what I have seen, they aren't a significant improvement over the basic quad draw workflow.
So you just build a new mesh directly on top of the old one, and then you bake from the old to the new. If you want symmetry that the original doesnt have that is no big deal. Just retopo half the model and then bake. Afterwards you can adjust the mirroring of your UV's as needed.
That sounds simple but there is quite a few substeps of course. But just like, commit a week to practice basic baking and you'll get it. A simple practice exercise would be to take the tiger, duplicate it, assign a new material to the duplicate, flip its UV's around, then bake the old models textures onto the new one. This will help you understand the basic idea - that you can transfer info from one model to another so long as the surface geometry is close enough together.
Another thing you can do - something I do a lot - is get some free scanned items from sketchfab (liek a pair of shoes for instance), set that scan to be a live mesh in maya, retopo it using quad draw tools, and then bake the scans textures onto your new game appropriate topology. Same idea in action.
Well, first of all the model you linked is far from being as wonky as you make it sound ... The meshing is clean and the unwrap is flawless. It not having a centerline is a bit odd but nothing crazy, and the split edges are trivial to fix and seem to just be the consequence of a conversion that split the model according to the UVs. They're in no way a consequence of bad modeling.
Anyways. You need to be familiar with three things :
1-being confortable with unwrapping models (which indeed can be easily done over an existing texture - it's just a matter of using similar seams)
2-baking textures from a source model to a target model - which, as complex as it may sound, is something that 100% of game artists managed to learn. I am sure you can too.
3-baking textures within a single model from one UV channel to another, which is a very elegant way of optimising a texture like here.
To anwrap a mesh to another mesh existing UV you just need to project that UV from one mesh to another . Both Maya attribute transfer, Max projection modifier and Blender data transfer modifier can do it. Sometimes it may take a few manual fixes around seams although .
There is also a special soft that can directly wrap one mesh over another https://www.russian3dscanner.com/