Hard edges vs soft edges

Development Asset Creation
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1

My question relates to this paragraph from the Unreal Performance guide; Limit UV seams and hard edges as it results in more vertices for the hardware. In the worst case, high poly meshes with hard edges result in 3 times more vertices than reported in modelling applications.

The difference in cost is clear to me but what I am wondering is if I import a hard edged model from Maya and then use a normal map to average/soften out the vertex normals in Unreal, is that normal map changing the edge quality of the mesh in Unreal or am I locked into the edge softness/hardness that the mesh had on import? Essentially what I am asking is; can a normal map avoid the 3x extra cost that is associated with hard edged models in UE?

I appreciate any help clarifying this.

2

No, normal maps are just textures laid on top of a model, it still has all those splits.

Generally you don’t really need to worry much about hard edges, polycount isn’t a huge concern on modern hardware. The biggest thing is you need to know is hard edges require matching UV splits to get normal maps to work without artifacts.