1. why soft edge and hard edge is imp?Is it because, I wanna show this edge more prominently comparing to others?Or it also has some other job to do??
Something like, a pipe will have soft edge in the main body but the the outline of a groove, the edge should be hard.
The edge that pass through are white are soft edges and the ones indicated by red lines are hard edge.
and what is the meaning of edges having angle between 0 to 180?is it like soft hard edge?
2. Normal map don't work correctly if the hard edges are not kept separate.It is most likely those edges(!) has two normals of different angles.
so, it there any method of making a hard edge smooth without costing extra polygon.