@ecoin you are clearly undertaking a major and and detailed project which has discovered some bugs within the creation of Babylon.js meshes regarding text orientation. This can be very frustrating. What I am attempting to do is to analyse what and where the bugs are so they can be accurately presented to the core team along with possible solutions.
Depending where you see the light coming from you can see the 2D normal texture as having bumps or indents. I would argue that, like the left handed system, going for bumps and indents is a choice not a bug. Unrecei
ved expectations are not always a bug. You could argue that it is a wrong choice, however whether it is a bug or a wrong choice there is a way of applying a correction.
The cylinder and sphere are different issues. The text on the cylinder is reflected and no matter how you rotate the cylinder the text will remain reflected. The issue with the sphere is a viewing one, a rotation of 180o corrects the view.
Whilst what I said above is true on second thoughts it is not the only way, assigning uv values differently to vertices during mesh construction would solve some of the issues. For example in the following PG the text direction is corrected with external faceUV, with an added parameter to CreateCylinder something similar could be done on construction.
Not sure how you created the wall in your example, using a hole, as in this
PG wall.
Like the cylinder the polygon text issue for all faces would not be solved by the three functions I suggested
Sorry if I was not clear but to correct for RHS number 2 would also be necessary and applied first.
I have put forward some solutions in the feature request section 