What would be the point baking from multiple highres meshes onto a single lowres mesh? If you have a single lowres mesh, use a single highres mesh.
To avoid baking artifacts from neighboring parts. For game assets, sometimes it's best to have a single mesh, but to get a good bake with a mesh that has parts close to each other, wouldn't multi-mesh bake be best, but then you have to handle going back to the single mesh?
What do you mean by 'low poly single mesh with multiple material IDs'? You have a lowres mesh and created multiple TextureSets from material assignments?
Yes, multiple material id's mean multiple texture sets.
Having multiple highres meshes only makes sense if you have multiple corresponding lowres meshes and want to use the 'match by mesh name' feature. You can have a single lowres mesh and multiple highres meshes, it won't have any influence on anything though (in comparison to having a single highres mesh), and you can't use the 'match by mesh name' feature.
I understand that, but in this video series:
https://academy.substance3d.com/courses/substance-painter-model-preparation/youtube-3pft-kodkg0..at the end, Wes ends up with a high res fbx file with multi high res parts, a low res fbx with mult parts and an ID fbx with only 2 low res parts, but doesn't show what he uses in painter. I understand he can use the high res if he only wants high res mult mesh, he could also use the low res multi part and take advantage of the bake by name and add in the high res multi part for the baking mesh, but what is the point of the ID fbx?
I got lost here and in other videos, people (Wes included) start out by creating a new painter project with an fbx low res, not specifying if it is single or multi part mesh, then when they get to explain the baking and bake by name do they illustrate going back into the modeling program and splitting the parts up into _low and _high. Which I assume at that point they have to then use an fbx _low with multi meshes.
But there is a disconnect in my thinking I am asking about here. It seems if painter can separate texture sets based on material IDs, could it also bake the parts of the mesh like this too without needing the mesh to be actually split in multi-mesh _low parts?
Wes in some other videos (the lantern series) explained baking ID artifacts that were solved by splitting up the mesh into _low and _high parts. I thought since this has to do with IDs, maybe the painter project mesh doesn't need to split up and can be a single mesh but with multiple mat IDs/texture sets...so I was asking if the single mesh used in painter (in my case my low res single mesh model) can utilize the bake by name feature using an fbx _high multi part mesh that has the same material IDs as what's on the low res single mesh model? Meaning, painter's bake by name would focus on the material IDs to bake regardless of the meshes (project mesh and fbx _high multi-mesh bake mesh) being single or mult.
That way I can put together my low res single mesh in my modeling program that has the mat IDs setup, and in painter, utilize the good bake by name separation using a _high res parted out fbx, and in the end still use my single low res mesh with good bake and IDs/texture sets separated which is my goal.