It seems to me like this is something very much outside the scope of MyPaint. Isn’t it easier to just use e.g. Blender together with a texture reloading add-on (https://github.com/samytichadou/Auto_Reload_Images-Blender_addon)? That way you can work on your texture in MyPaint and see the results using Blender’s render preview.
Additionally, normal maps are often created for use with specific geometry, so I don’t see a generic flat preview being very useful. Apart from that, isn’t it very unusual to work with normal maps manually, except for minor edits? My experience is that they are almost always generated in one way or another.
I think the issue is misunderstood here. This isn’t a 3d model. This is a 2d drawing, with a painted normal map. I’m not doing anything with textures at this point.
It is a bit niche, but it is it’s own medium and can give you better results than generated normal maps. Typically hand drawn normal maps are done in photoshop because of the 3d preview it has.
I’ll give blender a shot, but I’m not a 3d artist and have never touched the software before.
Ah, I sort of understand the use-case now. I still think this is out-of-scope for MyPaint, but I can see where it might be useful for asset-generation. Out of curiosity, do you have any links to tutorials or examples of this kind of workflow?
To me it seems more clunky and less powerful than “just using blender”, but I tend to forget the amount of time I had to spend with 3d-software back in the day to reach my current proficiency.