Many thanks to them!
For comparison, see here:
http://kishalmi.servus.at/3D/bumpcode/
Based on algorithm in: Mikkelsen M. S.: Simulation of Wrinkled Surfaces Revisited.
http://jbit.net/~sparky/sfgrad_bump/mm_sfgrad_bump.pdf
This fixes bugs:
#24591: Artefacts/strange normal mapping when anti-aliasing is on
#24735: Error at the Normal function.
#24962: Normals are not calculated correctly if anti-aliasing is off
#25103: Weird artefacts in Normal
This will break render compatibility a bit, but fixing this bugs would have also
done that, so in this case it should be acceptable.
Patch committed with these modifications:
* Bump method Old/3-Tap/5-Tap option in UI, 3-Tap is default
* Only compute normal perturbation vectors when needed
* Fix some middle of block variable definitions for MSVC