Hi! In Blender (4.1), going into edit mode, you can preview the split vertex normals (taking into account hard edges) here: Functions to modify the vertex normals manually, with vertices selected in edit mode, can be found under "Mesh > Normals > ..." - or shortcut "alt + N": To flatten the vertex normals, you would copy…
Yeah heavy gradients in a tangent space normal map or differences in shading between the low and high poly causes: More shading errors if the baked normal map tangent space isn't synced with the engine More shading errors if there's not enough resolution More shading errors the heavier the texture compression More obvious…