Reference Cinema 4D Basic Features BodyPaint 3D Select Bitmap Menu
Function available in CINEMA 4D Prime, Visualize, Broadcast, Studio & BodyPaint 3D

Feather

Feather...

Feather softens the edges of an existing selection. A dialog appears when you select the command. Enter the width of the feathering — you can enter values from 0 to 1,000. Click OK to apply the feathering.