I created normal map from high resolution sculpting. And connect it to glossy shader with minimal number of roughness. When i rendered it in Cycles plane object looks like shading flat, but it smooth.
normal map is 2048x2048
multiresolution is very high at 10
i tried it for glossy shader as same as for anisotropic shader. The result is same thing.
for other 2048x2048 normal map same result (flatness jagged artefacts)
File format and color depth of the normal map?
File format PNG color depth 24 bit / 8 bit per channel /
And if that’s not enough, you can always switch to use cubic interpolation instead of linear.
the problem is still exist
For normal maps, it’s better to use PNG48 (16bpc) or EXR (fp16/32). 8 bits per channel will lead to precision errors.