I am pretty new to Unity and after hours of searching I have finally figured out how to set everything up for (baked) global illumination to work for my model.
However the model is an export from a CAD program and so the mesh is rather bad quality (it seems it is optimized by the CAD program for minimum number of triangles). At least I am implicitely assuming that this is a bad quality mesh because it would by standard of finite element meshes, which of course doesn't directly apply here.
So what I am observing is three resolution problems (see images):
1) the lighting in the scene is somewhat "cloudy" although the faces are evenly colored and there are no lights that could explain the patterns (see eg. area inside drawn red rectangle)
2) there are slight jumps in brightness visible at the edges of the triangles of the mesh (see red arrows and, for comparison image of mesh)
3) the shadows are pixelated (see red ellipse, yes I have already tried to change shadow quality to high in the project settings, but to no avail)
Because there are so many settings that affect lighting, I assume it will take me hours if not days with trial and error to figure that out.
Which settings are likely to be responsible for these three problems?
I found a display mode of the scene view, called: Baked Global Illumination->UV Charts that probably explains the first problem, but I don't know how to interpret it, see third image below: