alrighty here's a question for you (just read your post about answering 3D modeling questions - big agree on tumblrs format being much better for that sort of thing)
so i run a vroid model, and i would really like to make new outfits and hair styles for my model without having to redo all the blendshapes, animated textures, etc.
is there a way to take another model and slap an existing face on it (maybe in blender)?
whether or not this is a question you're able to answer thanks very much for reading. love your work and i hope you can thrive here on tumblr!
hi! do note when i answer any of these questions, this is coming from the POV of someone who has never worked with vroid but im fairly and confidently familiar with the <1.0 vrm format.
the best solution i can give you in terms of creating new outfits and hair is to have a base model made (a base model without hair or clothing with the base characteristics/textures/etc retained). however, i'm not sure how feasible this is with vroid, given that it's a program i'm not super familiar with.
HOWEVER, if you're familiar with unity, and if not i 100% implore you to begin familiarizing yourself with the game engine as .vrm and vrm-reading vtubing software run off of unity. UniVRMExtensions, a modified iteration of the UniVRM unitypackage for importing, editing, and exporting vrm files in unity, can be used to copy and paste blendclip data from one model to another. i've used it for a good handful of months now and i can attest to it's usefulness in some scenarios like the one you're talking about.
UniVRMExtensions doesn't use the most recent version of UniVRM, which shouldnt really be an issue. the version used by univrmextensions also doesn't outdate vsfavatar if you happen to use that format as well.
materials, regardless of their properties, can be dragged and dropped onto meshes in unity, or those material properties can be copied and pasted from one material to another. the tutorial im linking here is for component copy and pasting, but it works in the scenario i'm referring to as well.
as for removing heads for replacement in blender, it's as simple as importing the vrm using saturday06's vrm addon to import your model, expanding the armature, and deleting whatever the head mesh is called by either deleting it from the outliner window or directly from the viewport (see an outliner screenshot below this paragraph).
also, fun tip! you can open up a separate instance of blender, import the vrm of the model with meshes you want to bring into the original one you want replaced, select that head mesh, go to the modifier tab (as shown in the next screenshot) and delete the armature. you can then ctrl+c to copy the mesh when selected in the viewport. if you do not delete the armature beforehand, the skeleton and likely any objects or other components that are connected to that armature will carry with the head you want to copy.
you can then go into your original blender instance where you want to paste the head, ctrl+v, and then go back to the modifier tab, select the armature modifier, and in the object box, select the armature of the vrm model. double check and make sure your head still has it's vertex groups, as it should, by selecting the model's armature and going into pose mode, as shown here in the upper left corner of the screen.
rotate or move the head and neck bones, as well as the eyes, and if everythings still working, press A to select all the bones and right click, and selecting Clear User Transforms to reset the pose. you should be good then to reexport to vrm and bring the model into unity, and either copying the blendclips using the extension i've talked about previously or remaking the shapekeys (if you use arkit) using HANA Tool's clipbuilder, which can create the blendclips for the arkit shapekeys you already have made for your model's head; i use it for my own from scratch models to save time when porting to VRM format. this specific tool from this unitypackage does NOT remake your shapekeys, to clarify; just creates blendclips with the ones already existing on your model.
i hope this helps, apologies if this is a lot!