Recently, me and my colleague stumbled upon a particularly weird issue in whish Painter's performance was so low that it was loading each Texture Set for 15 minutes upon switching.
To put it into more detail, we are working on a project that requires hand-painted masks. The way we're doing it is simply by creating new Fill Layers with black masks and just drawing on them. All work files are just meshes imported into fresh scenes without any baked textures. Which is another point - there are no generators or procedular masks used on Fill Layers. Just brushes. Texture Sets don't even have Normals or AOs.
I should also note that we're painting in both 2k and 4k resolutions and it doesn't make much of a difference. Disabling other Materials from the view eases the pain slightly, but not enough unfortunately.
By my understanding Painter has troubles saving custom drawn masks, because the way it saves them is entirely different from saving generators. Am I right to assume that masks with generators are just a bunch of numbers that are easily saved, meanwhile custom drawn masks are harder to save because they're projections? I'd need some confirmation on that point as I'd really like to know what's going on here.
In addition, we've tried every solution listed in Performance guides and none of that helped.
Substance version tests
Adobe Substance 3D Painter ver 7.2.1
We've tried newer version, which was 7.2.1 and it was probably the biggest performance loss on that version, it couldn't even handle 4 layers on each Texture Set (each on 1k resolution) and switching between them took up to 5 minutes).
Substance Painter 2020 6.2.2
This was the main version we've been working with for the last year and it was good until this particular issue.