How to calculate the object space normal map based on the low-poly mesh and tangent space normal map

How to calculate normals with tangent space normal map connected.
Or, how to convert the low-poly mesh and tangent space normal map to object space normal map.
image

My implementation results are not quite the same as those in Blender, but the source code is a bit hard to read for beginners, so I would appreciate some guidance(reference documents or links) from my predecessors.

Thanks~

Hi jinhao-luo,

This forum is only for development-related questions. Are you asking about specifics of certain functions in Blender’s source code? If so, it’ll be clearer if you directly mention which functions you’re asking about.

If this is not about development of Blender itself, your message is unfortunately out of scope of this forum (check the blue bar at the top for links to potentially better-suited places).

Sybren