Baking. Soft VS hard normals on low poly mesh.

somawheels

When you bake a highpoly mesh onto a lowpoly mesh, should you give the lowpoly mesh hard or soft face-normals?

Alex_J

depends if you need the edge to look soft or hard.

https://polycount.com/discussion/107196/youre-making-me-hard-making-sense-of-hard-edges-uvs-normal-maps-and-vertex-counts#latest

gnoop

The edges where UV seams are  could be split/hard /sharp  since a game engine would split such edges anyway and edge vertex count will be doubled at such edges.

Any other edges should be smooth/soft  and making them hard  where no UV seems are  just makes extra redundant vertexes to calculate  and troubles for normal map baking. 

If adjacent  faces within same UV island are 90 degree to each other  it should rather have bevel /chamfer  with its vertex normals edited/rotated perpendicularly to those faces . It's necessary to get rid of smooth shading gradients on what supposed to be flat surface.

There is no problem to make hard/sharp edge looking beveled or rounded  by means of  normal map only (if necessary) . It just needs a special approach. A support edge loop along that sharp edge with perfectly perpendicular vertex normals.  After normal map baking such loops must be deleted.