If using Directx, refer to Directx sample about Normal Map. For example, Directx12 chapter 19, normal map. There is code sample shows how to create it.
And it's necessary to create normal map using shader.
This is a signature. Any samples given are not meant to have error checking or show best practices. They are meant to just illustrate a point. I may also give inefficient code or introduce some problems to discourage copy/paste coding. This is because
the major point of my posts is to aid in the learning process.