Cinema 4D / BodyPaint 3D Program Documentation Reference BodyPaint 3D Select Bitmap Menu
Function available in CINEMA 4D Prime, Visualize, Broadcast, Studio & BodyPaint 3D

Grow Selection

Use this command to expand a selection by a specified number of pixels. A value of between 1 and 100 can be entered. Selections that are expanded larger than the texture surface will be cut off at the texture’s edge.