The tySmooth modifier is an optimized and multi-threaded version of 3ds Max’s built-in smooth modifier.
Auto Smooth: When disabled, no mesh faces will share smoothing groups. When enabled, mesh faces will be assigned smoothing groups based on the angles between their adjacent faces.
Prevent indirect smoothing: re-processes smoothing groups generated by the auto-smooth function, in order to prevent indirect smoothing.
Indirect smoothing happens when adjacent faces (which do not satisfy the angle threshold condition) end up as members of the same smoothing group because they are connected by other adjacent faces which do satisfy the angle threshold condition. “Prevent indirect smoothing” attempts to rectify this problem by shuffling smoothing groups in a way that keeps properly-smoothed adjacent faces as members of the same group, while keeping indirectly-smoothed adjacent faces as members of different groups. Enabling this feature has a performance cost that will cause the auto-smooth algorithm to run slower.
Protect MatID boundaries: when enabled, faces with different material ID values will not be added to the same smoothing groups.
Threshold: the angle threshold to use, to compare adjacent faces. If the angle between adjacent faces is less than this value, they will be assigned to the same smoothing group.
If “remove explicit normals” is disabled, meshes with explicit normals assigned to them may appear to be unaffected by the tySmooth modifier, because even though tySmooth will change the mesh’s smoothing groups, the smoothing group change will have no effect on the mesh’s visual appearance.